From b9c9bb264b0c9853a89493d0975ad40c47002b01 Mon Sep 17 00:00:00 2001
From: alemuntoni <muntoni.alessandro@gmail.com>
Date: Fri, 4 Nov 2022 10:41:49 +0100
Subject: [PATCH 1/4] remove nexus submodule and download it using cmake

---
 .gitmodules                                   |  3 ---
 src/external/newuoa.cmake                     |  4 +--
 src/external/nexus                            |  1 -
 src/external/nexus.cmake                      | 27 ++++++++++++++++---
 .../filter_io_nxs/CMakeLists.txt              |  4 +--
 5 files changed, 27 insertions(+), 12 deletions(-)
 delete mode 160000 src/external/nexus

diff --git a/.gitmodules b/.gitmodules
index a892ada73..90e29d2f6 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -2,6 +2,3 @@
 	path = src/vcglib
 	url = https://github.com/cnr-isti-vclab/vcglib
 	branch = devel
-[submodule "src/external/nexus"]
-	path = src/external/nexus
-	url = https://github.com/cnr-isti-vclab/nexus
diff --git a/src/external/newuoa.cmake b/src/external/newuoa.cmake
index 73821e8fe..3f065ae7d 100644
--- a/src/external/newuoa.cmake
+++ b/src/external/newuoa.cmake
@@ -2,11 +2,11 @@
 # Copyright 2019, 2020, Visual Computing Lab, ISTI - Italian National Research Council
 # SPDX-License-Identifier: BSL-1.0
 
-option(ALLOW_BUNDLED_NEWUOA "Allow use of bundled newuoa source" ON)
+option(MESHLAB_ALLOW_BUNDLED_NEWUOA "Allow use of bundled newuoa source" ON)
 
 set(NEWUOA_DIR ${VCGDIR}/wrap/newuoa)
 
-if(ALLOW_BUNDLED_NEWUOA AND EXISTS "${NEWUOA_DIR}/include/newuoa.h")
+if(MESHLAB_ALLOW_BUNDLED_NEWUOA AND EXISTS "${NEWUOA_DIR}/include/newuoa.h")
 	message(STATUS "- newuoa - using bundled source")
 	add_library(external-newuoa INTERFACE)
 	target_include_directories(external-newuoa INTERFACE ${NEWUOA_DIR}/include)
diff --git a/src/external/nexus b/src/external/nexus
deleted file mode 160000
index 9f56edab7..000000000
--- a/src/external/nexus
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 9f56edab7cf80d2d4a654e65be087ebd973f66bd
diff --git a/src/external/nexus.cmake b/src/external/nexus.cmake
index 1e1d1e69a..d8bccf0aa 100644
--- a/src/external/nexus.cmake
+++ b/src/external/nexus.cmake
@@ -2,12 +2,31 @@
 # Copyright 2019, 2020, Visual Computing Lab, ISTI - Italian National Research Council
 # SPDX-License-Identifier: BSL-1.0
 
-option(ALLOW_BUNDLED_NEXUS "Allow use of bundled nexus source" ON)
+option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS "Allow download and use of nexus source" ON)
+
+if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS)
+	# todo - make release of nexus and corto
+	set(NEXUS_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/nexus-master)
+	set(CORTO_DIR ${NEXUS_DIR}/src/corto)
+
+	if (NOT EXISTS "${NEXUS_DIR}/CMakeLists.txt")
+		set(NEXUS_LINK https://github.com/cnr-isti-vclab/nexus/archive/refs/heads/master.zip)
+		download_and_unzip(${NEXUS_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "nexus")
+	endif()
+
+	if (NOT EXISTS "${CORTO_DIR}/CMakeLists.txt")
+		file(REMOVE_RECURSE ${NEXUS_DIR}/src/corto)
+		set(CORTO_LINK https://github.com/cnr-isti-vclab/corto/archive/refs/heads/master.zip)
+		download_and_unzip(${CORTO_LINK} "${NEXUS_DIR}/src/" "corto")
+		file(RENAME ${NEXUS_DIR}/src/corto-master ${NEXUS_DIR}/src/corto)
+	endif()
+
+	message(STATUS "- nexus - using downloaded source")
 
-if(ALLOW_BUNDLED_NEXUS AND EXISTS "${CMAKE_CURRENT_LIST_DIR}/nexus/CMakeLists.txt")
-	message(STATUS "- nexus - using bundled source")
 	set (BUILD_NXS_BUILD OFF)
 	set (BUILD_NXS_EDIT OFF)
 	set (BUILD_NXS_VIEW OFF)
-	add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/nexus EXCLUDE_FROM_ALL)
+	add_subdirectory(${NEXUS_DIR} EXCLUDE_FROM_ALL)
+	add_library(external-nexus INTERFACE)
+	target_link_libraries(external-nexus INTERFACE nexus)
 endif()
diff --git a/src/meshlabplugins/filter_io_nxs/CMakeLists.txt b/src/meshlabplugins/filter_io_nxs/CMakeLists.txt
index bfe48051c..c6b734348 100644
--- a/src/meshlabplugins/filter_io_nxs/CMakeLists.txt
+++ b/src/meshlabplugins/filter_io_nxs/CMakeLists.txt
@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: BSL-1.0
 
 # Only build if we have nexus
-if (TARGET nexus)
+if (TARGET external-nexus)
 
 	set(SOURCES filter_io_nxs.cpp)
 
@@ -10,7 +10,7 @@ if (TARGET nexus)
 
 	add_meshlab_plugin(filter_io_nxs MODULE ${SOURCES} ${HEADERS})
 
-	target_link_libraries(filter_io_nxs PRIVATE nexus)
+	target_link_libraries(filter_io_nxs PRIVATE external-nexus)
 
 else()
 	message(STATUS "Skipping filter_io_nxs - missing nexus")

From 468990d34645fa34fd79cd1b5ba46b7990549edb Mon Sep 17 00:00:00 2001
From: alemuntoni <muntoni.alessandro@gmail.com>
Date: Fri, 4 Nov 2022 12:20:48 +0100
Subject: [PATCH 2/4] better management of download archives

---
 src/cmake/meshlab_tools.cmake |  36 +++++++----
 src/external/boost.cmake      |  21 +++++--
 src/external/cgal.cmake       | 110 ++++++++++++++++++++--------------
 src/external/e57.cmake        |  29 +++++----
 src/external/easyexif.cmake   |  21 +++++--
 src/external/glew.cmake       |  39 +++++++-----
 src/external/levmar.cmake     |  40 ++++++++-----
 src/external/lib3ds.cmake     | 106 +++++++++++++++++---------------
 src/external/libigl.cmake     |  21 +++++--
 src/external/muparser.cmake   |  36 ++++++-----
 src/external/nexus.cmake      |  45 +++++++++-----
 src/external/openctm.cmake    |  57 ++++++++++--------
 src/external/qhull.cmake      |  32 ++++++----
 src/external/ssynth.cmake     |  28 +++++----
 src/external/tinygltf.cmake   |  21 +++++--
 src/external/u3d.cmake        |  39 +++++++-----
 src/external/xerces.cmake     |  43 +++++++------
 17 files changed, 448 insertions(+), 276 deletions(-)

diff --git a/src/cmake/meshlab_tools.cmake b/src/cmake/meshlab_tools.cmake
index a0a6972ee..9e2c0f77b 100644
--- a/src/cmake/meshlab_tools.cmake
+++ b/src/cmake/meshlab_tools.cmake
@@ -35,19 +35,35 @@ endfunction()
 # - link: download link
 # - dir: directory where the archive will be extracted
 # - name: a name used only for log
-function(download_and_unzip link dir name)
+function(download_and_unzip)
+	set(download_and_unzip_SUCCESS FALSE PARENT_SCOPE)
+	set(options)
+	set(oneValueArgs SHA NAME DIR)
+	set(multiValueArgs LINK)
+	cmake_parse_arguments(DAU
+		"${options}" "${oneValueArgs}"
+		"${multiValueArgs}" ${ARGN})
+
+	list(LENGTH DAU_LINK NUMBER_OF_LINKS)
+	if(NUMBER_OF_LINKS LESS 1)
+		message(FATAL_ERROR "Need to specify at least a download link.")
+	endif()
+
 	set(ZIP ${CMAKE_CURRENT_LIST_DIR}/tmp.zip)
 
-	message(STATUS "Downloading ${name}...")
+	foreach(LINK ${DAU_LINK})
+		message(STATUS "Downloading ${DAU_NAME} from ${LINK}")
 
-	file(DOWNLOAD ${link} ${ZIP})
-	message(STATUS "${name} downloaded.")
-	message(STATUS "Extracting ${name} archive...")
-	file(ARCHIVE_EXTRACT
-		INPUT ${ZIP}
-		DESTINATION ${dir})
-	message(STATUS "${name} archive extracted.")
-	file(REMOVE ${ZIP})
+		file(DOWNLOAD ${LINK} ${ZIP})
+		message(STATUS "${DAU_NAME} downloaded.")
+		message(STATUS "Extracting ${DAU_NAME} archive...")
+		file(ARCHIVE_EXTRACT
+			INPUT ${ZIP}
+			DESTINATION ${DAU_DIR})
+		message(STATUS "${DAU_NAME} archive extracted.")
+		file(REMOVE ${ZIP})
+		set(download_and_unzip_SUCCESS TRUE PARENT_SCOPE)
+	endforeach()
 endfunction()
 
 # make quiet some portions of cmake
diff --git a/src/external/boost.cmake b/src/external/boost.cmake
index ae696746f..46ea6fa20 100644
--- a/src/external/boost.cmake
+++ b/src/external/boost.cmake
@@ -15,14 +15,23 @@ if(MESHLAB_ALLOW_SYSTEM_BOOST AND TARGET Boost::boost)
 		target_link_libraries(external-boost INTERFACE Boost::thread)
 	endif()
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_BOOST)
-	set(BOOST_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/boost_1_75_0)
+	set(BOOST_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/boost_1_75_0")
+	set(BOOST_CHECK "${BOOST_DIR}/boost/version.hpp")
 
-	if (NOT EXISTS "${BOOST_DIR}/boost/version.hpp")
+	if (NOT EXISTS ${BOOST_CHECK})
 		set(BOOST_LINK https://boostorg.jfrog.io/artifactory/main/release/1.75.0/source/boost_1_75_0.zip)
-		download_and_unzip(${BOOST_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "Boost")
+		download_and_unzip(
+			LINK ${BOOST_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "Boost")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- Boost - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- Boost - using downloaded source")
-	add_library(external-boost INTERFACE)
-	target_include_directories(external-boost INTERFACE "${BOOST_DIR}")
+	if (EXISTS ${BOOST_CHECK})
+		message(STATUS "- Boost - using downloaded source")
+		add_library(external-boost INTERFACE)
+		target_include_directories(external-boost INTERFACE "${BOOST_DIR}")
+	endif()
 endif()
diff --git a/src/external/cgal.cmake b/src/external/cgal.cmake
index 9240796bb..ddeb7a2c0 100644
--- a/src/external/cgal.cmake
+++ b/src/external/cgal.cmake
@@ -14,57 +14,77 @@ if(MESHLAB_ALLOW_SYSTEM_CGAL AND TARGET CGAL::CGAL)
 	target_link_libraries(external-cgal INTERFACE CGAL::CGAL Threads::Threads)
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_CGAL)
 	set(CGAL_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/CGAL-5.2.1")
+	set(CGAL_CHECK "${CGAL_DIR}/include/CGAL/version.h")
+	set(CGAL_WIN_CHECK "${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.lib")
 
-	if (NOT EXISTS "${CGAL_DIR}/include/CGAL/version.h")
+	set(CGAL_DOWNLOAD_SUCCESS TRUE)
+
+	if (NOT EXISTS ${CGAL_CHECK})
 		set(CGAL_LINK https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1.zip)
-		download_and_unzip(${CGAL_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "CGAL")
+		download_and_unzip(
+			LINK ${CGAL_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "CGAL")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- CGAL - download failed.")
+			set(CGAL_DOWNLOAD_SUCCESS FALSE)
+		endif()
+	endif()
+
+	if (WIN32 AND NOT EXISTS ${CGAL_WIN_CHECK})
+		set(CGAL_AUX_LINK https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1-win64-auxiliary-libraries-gmp-mpfr.zip)
+		download_and_unzip(
+			LINK ${CGAL_AUX_LINK}
+			DIR ${CGAL_DIR}
+			NAME "CGAL auxiliary libraries")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- CGAL auxiliary libraries - download failed.")
+			set(CGAL_DOWNLOAD_SUCCESS FALSE)
+		endif()
+	endif()
+
+	if (CGAL_DOWNLOAD_SUCCESS)
+		message(STATUS "- CGAL - using downloaded source")
+		add_library(external-cgal INTERFACE)
+		target_include_directories(external-cgal INTERFACE "${CGAL_DIR}/include/")
 
 		if (WIN32)
-			set(CGAL_AUX_LINK https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1-win64-auxiliary-libraries-gmp-mpfr.zip)
-			download_and_unzip(${CGAL_AUX_LINK} ${CGAL_DIR} "CGAL auxiliary libraries")
+			add_library(mpfr SHARED IMPORTED GLOBAL)
+			set_property(TARGET mpfr PROPERTY IMPORTED_IMPLIB "${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.lib")
+			set_property(TARGET mpfr PROPERTY IMPORTED_LOCATION "${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.dll")
+			target_include_directories(mpfr INTERFACE "${CGAL_DIR}/auxiliary/gmp/include")
+
+			add_library(gmp SHARED IMPORTED GLOBAL)
+			set_property(TARGET gmp PROPERTY IMPORTED_IMPLIB "${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.lib")
+			set_property(TARGET gmp PROPERTY IMPORTED_LOCATION "${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.dll")
+			target_link_libraries(external-cgal INTERFACE gmp mpfr Threads::Threads)
+		else()
+			find_package(GMP)
+			target_include_directories(external-cgal SYSTEM INTERFACE ${GMP_INCLUDE_DIRS})
+			target_link_libraries(external-cgal INTERFACE ${GMP_LIBRARIES} mpfr Threads::Threads)
 		endif()
-	endif()
 
-	message(STATUS "- CGAL - using downloaded source")
-	add_library(external-cgal INTERFACE)
-	target_include_directories(external-cgal INTERFACE "${CGAL_DIR}/include/")
-
-	if (WIN32)
-		add_library(mpfr SHARED IMPORTED GLOBAL)
-		set_property(TARGET mpfr PROPERTY IMPORTED_IMPLIB "${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.lib")
-		set_property(TARGET mpfr PROPERTY IMPORTED_LOCATION "${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.dll")
-		target_include_directories(mpfr INTERFACE "${CGAL_DIR}/auxiliary/gmp/include")
-
-		add_library(gmp SHARED IMPORTED GLOBAL)
-		set_property(TARGET gmp PROPERTY IMPORTED_IMPLIB "${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.lib")
-		set_property(TARGET gmp PROPERTY IMPORTED_LOCATION "${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.dll")
-		target_link_libraries(external-cgal INTERFACE gmp mpfr Threads::Threads)
-	else()
-		find_package(GMP)
-		target_include_directories(external-cgal SYSTEM INTERFACE ${GMP_INCLUDE_DIRS})
-		target_link_libraries(external-cgal INTERFACE ${GMP_LIBRARIES} mpfr Threads::Threads)
-	endif()
-
-	if (WIN32)
-		if (DEFINED MESHLAB_LIB_OUTPUT_DIR)
-			file(
-				COPY
-					${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.lib
-					${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.dll
-					${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.lib
-					${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.dll
-				DESTINATION
-					${MESHLAB_LIB_OUTPUT_DIR})
-		endif()
-		if (DEFINED MESHLAB_LIB_INSTALL_DIR)
-			install(
-				FILES
-					${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.lib
-					${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.dll
-					${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.lib
-					${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.dll
-				DESTINATION
-					${MESHLAB_LIB_INSTALL_DIR})
+		if (WIN32)
+			if (DEFINED MESHLAB_LIB_OUTPUT_DIR)
+				file(
+					COPY
+						${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.lib
+						${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.dll
+						${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.lib
+						${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.dll
+					DESTINATION
+						${MESHLAB_LIB_OUTPUT_DIR})
+			endif()
+			if (DEFINED MESHLAB_LIB_INSTALL_DIR)
+				install(
+					FILES
+						${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.lib
+						${CGAL_DIR}/auxiliary/gmp/lib/libmpfr-4.dll
+						${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.lib
+						${CGAL_DIR}/auxiliary/gmp/lib/libgmp-10.dll
+					DESTINATION
+						${MESHLAB_LIB_INSTALL_DIR})
+			endif()
 		endif()
 	endif()
 else()
diff --git a/src/external/e57.cmake b/src/external/e57.cmake
index 61968cf4b..af27fae05 100644
--- a/src/external/e57.cmake
+++ b/src/external/e57.cmake
@@ -6,22 +6,31 @@ option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIBE57 "Allow download and use of libE57For
 
 if (TARGET XercesC::XercesC)
 	if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIBE57)
-		set(LIBE57_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/libE57Format-2.3.0)
+		set(LIBE57_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/libE57Format-2.3.0")
+		set(LIBE57_CHECK "${LIBE57_DIR}/CMakeLists.txt")
 
-		if (NOT EXISTS ${LIBE57_DIR}/CMakeLists.txt)
+		if (NOT EXISTS ${LIBE57_CHECK})
 			set(LIBE57_LINK https://github.com/asmaloney/libE57Format/archive/refs/tags/v2.3.0.zip)
-			download_and_unzip(${LIBE57_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "LibE57")
+			download_and_unzip(
+				LINK ${LIBE57_LINK}
+				DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+				NAME "LibE57")
+			if (NOT download_and_unzip_SUCCESS)
+				message(STATUS "- LibE57 - download failed.")
+			endif()
 		endif()
 
-		message(STATUS "- libE57 - using downloaded source")
+		if (EXISTS ${LIBE57_CHECK})
+			message(STATUS "- libE57 - using downloaded source")
 
-		set(MESSAGE_QUIET ON)
-		add_subdirectory(${LIBE57_DIR} EXCLUDE_FROM_ALL)
-		unset(MESSAGE_QUIET)
+			set(MESSAGE_QUIET ON)
+			add_subdirectory(${LIBE57_DIR} EXCLUDE_FROM_ALL)
+			unset(MESSAGE_QUIET)
 
-		add_library(external-libE57 INTERFACE)
-		target_link_libraries(external-libE57 INTERFACE E57Format)
-		install(TARGETS E57Format DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+			add_library(external-libE57 INTERFACE)
+			target_link_libraries(external-libE57 INTERFACE E57Format)
+			install(TARGETS E57Format DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+		endif()
 	endif()
 else()
 	message(STATUS - "Cannot build e57 because Xerces dependence not satisfied.")
diff --git a/src/external/easyexif.cmake b/src/external/easyexif.cmake
index cddf15b67..ce18b8053 100644
--- a/src/external/easyexif.cmake
+++ b/src/external/easyexif.cmake
@@ -5,16 +5,25 @@
 option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_EASYEXIF "Allow download and use of EasyExif source" ON)
 
 if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_EASYEXIF)
-	set(EASYEXIF_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/easyexif-1.0)
+	set(EASYEXIF_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/easyexif-1.0")
+	set(EASYEXIF_CHECK "${EASYEXIF_DIR}/exif.h")
 
-	if (NOT EXISTS "${EASYEXIF_DIR}/exif.h")
+	if (NOT EXISTS ${EASYEXIF_CHECK})
 		set(EASYEXIF_LINK https://github.com/mayanklahiri/easyexif/archive/refs/tags/v1.0.zip)
-		download_and_unzip(${EASYEXIF_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "EasyExif")
+		download_and_unzip(
+			LINK ${EASYEXIF_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "EasyExif")
+		if (NOT download_and_unzip_SUCCESS)
+			message(FATAL_ERROR "- EasyExif - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- EasyExif - using downloaded source")
-	add_library(external-easyexif STATIC ${EASYEXIF_DIR}/exif.h ${EASYEXIF_DIR}/exif.cpp)
-	target_include_directories(external-easyexif PUBLIC ${EASYEXIF_DIR})
+	if (EXISTS ${EASYEXIF_CHECK})
+		message(STATUS "- EasyExif - using downloaded source")
+		add_library(external-easyexif STATIC ${EASYEXIF_DIR}/exif.h ${EASYEXIF_DIR}/exif.cpp)
+		target_include_directories(external-easyexif PUBLIC ${EASYEXIF_DIR})
+	endif()
 else()
 	message(
 		FATAL_ERROR
diff --git a/src/external/glew.cmake b/src/external/glew.cmake
index b1174370c..a304e0632 100644
--- a/src/external/glew.cmake
+++ b/src/external/glew.cmake
@@ -24,26 +24,35 @@ if(MESHLAB_ALLOW_SYSTEM_GLEW AND HAVE_SYSTEM_GLEW)
 		message(FATAL_ERROR "OpenGL not found or your CMake version is too old!")
 	endif()
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_GLEW)
-	set(GLEW_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/glew-2.2.0)
+	set(GLEW_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/glew-2.2.0")
+	set(GLEW_CHECK "${GLEW_DIR}/src/glew.c")
 
-	if (NOT EXISTS "${GLEW_DIR}/src/glew.c")
+	if (NOT EXISTS ${GLEW_CHECK})
 		set(GLEW_LINK https://github.com/nigels-com/glew/releases/download/glew-2.2.0/glew-2.2.0.zip)
-		download_and_unzip(${GLEW_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "GLEW")
+		download_and_unzip(
+			LINK ${GLEW_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "GLEW")
+		if (NOT download_and_unzip_SUCCESS)
+			message(FATAL_ERROR "- GLEW - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- GLEW - using downloaded source")
-	add_library(external-glew SHARED "${GLEW_DIR}/src/glew.c")
-	target_include_directories(external-glew SYSTEM PUBLIC ${GLEW_DIR}/include)
-	if(TARGET OpenGL::GL)
-		target_link_libraries(external-glew PUBLIC OpenGL::GL)
-	elseif(TARGET OpenGL::OpenGL)
-		target_link_libraries(external-glew PUBLIC OpenGL::OpenGL)
-	else()
-		message(FATAL_ERROR "OpenGL not found or your CMake version is too old!")
-	endif()
+	if (EXISTS ${GLEW_CHECK})
+		message(STATUS "- GLEW - using downloaded source")
+		add_library(external-glew SHARED "${GLEW_DIR}/src/glew.c")
+		target_include_directories(external-glew SYSTEM PUBLIC ${GLEW_DIR}/include)
+		if(TARGET OpenGL::GL)
+			target_link_libraries(external-glew PUBLIC OpenGL::GL)
+		elseif(TARGET OpenGL::OpenGL)
+			target_link_libraries(external-glew PUBLIC OpenGL::OpenGL)
+		else()
+			message(FATAL_ERROR "OpenGL not found or your CMake version is too old!")
+		endif()
 
-	target_link_libraries(external-glew PRIVATE external-disable-warnings)
-	install(TARGETS external-glew DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+		target_link_libraries(external-glew PRIVATE external-disable-warnings)
+		install(TARGETS external-glew DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+	endif()
 else()
 	message(
 		FATAL_ERROR
diff --git a/src/external/levmar.cmake b/src/external/levmar.cmake
index 7b71bd2a2..57ebb8648 100644
--- a/src/external/levmar.cmake
+++ b/src/external/levmar.cmake
@@ -5,25 +5,33 @@
 option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LEVMAR "Allow download and use of levmar source" ON)
 
 if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LEVMAR)
-	set(LEVMAR_VER 2.6)
-	set(LEVMAR_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/levmar-${LEVMAR_VER})
+	set(LEVMAR_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/levmar-2.6")
+	set(LEVMAR_CHECK "${LEVMAR_DIR}/lm.h")
 
-	if (NOT EXISTS "${LEVMAR_DIR}/lm.h")
-		set(LEVMAR_LINK http://users.ics.forth.gr/~lourakis/levmar/levmar-${LEVMAR_VER}.tgz)
-		download_and_unzip(${LEVMAR_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "Levmar")
+	if (NOT EXISTS ${LEVMAR_CHECK})
+		set(LEVMAR_LINK http://users.ics.forth.gr/~lourakis/levmar/levmar-2.6.tgz)
+		download_and_unzip(
+			LINK ${LEVMAR_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "Levmar")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- Levmar - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- levmar - using downloaded source")
+	if (EXISTS ${LEVMAR_CHECK})
+		message(STATUS "- levmar - using downloaded source")
 
-	set(HAVE_LAPACK 0 CACHE BOOL "Do we have LAPACK/BLAS?")
-	set(BUILD_DEMO OFF)
-	set(MESSAGE_QUIET ON)
-	add_subdirectory(${LEVMAR_DIR})
-	unset(MESSAGE_QUIET)
-	unset(HAVE_LAPACK)
-	unset(BUILD_DEMO)
+		set(HAVE_LAPACK 0 CACHE BOOL "Do we have LAPACK/BLAS?")
+		set(BUILD_DEMO OFF)
+		set(MESSAGE_QUIET ON)
+		add_subdirectory(${LEVMAR_DIR})
+		unset(MESSAGE_QUIET)
+		unset(HAVE_LAPACK)
+		unset(BUILD_DEMO)
 
-	add_library(external-levmar INTERFACE)
-	target_link_libraries(external-levmar INTERFACE levmar)
-	target_include_directories(external-levmar INTERFACE ${LEVMAR_DIR})
+		add_library(external-levmar INTERFACE)
+		target_link_libraries(external-levmar INTERFACE levmar)
+		target_include_directories(external-levmar INTERFACE ${LEVMAR_DIR})
+	endif()
 endif()
diff --git a/src/external/lib3ds.cmake b/src/external/lib3ds.cmake
index e06ac9bb7..5c03328e5 100644
--- a/src/external/lib3ds.cmake
+++ b/src/external/lib3ds.cmake
@@ -13,57 +13,65 @@ if(MESHLAB_ALLOW_SYSTEM_LIB3DS AND TARGET Lib3ds::Lib3ds)
 	add_library(external-lib3ds INTERFACE)
 	target_link_libraries(external-lib3ds INTERFACE Lib3ds::Lib3ds)
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIB3DS)
-	set(LIB3DS_VER 1.3.0)
-	set(LIB3DS_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/lib3ds-${LIB3DS_VER})
+	set(LIB3DS_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/lib3ds-1.3.0")
+	set(LIB3DS_CHECK "${LIB3DS_DIR}/lib3ds/types.h")
 
-	if (NOT EXISTS "${LIB3DS_DIR}/lib3ds/types.h")
-		set(LIB3DS_LINK http://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/lib3ds/lib3ds-${LIB3DS_VER}.zip)
-		download_and_unzip(${LIB3DS_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "Lib3DS")
+	if (NOT EXISTS ${LIB3DS_CHECK})
+		set(LIB3DS_LINK http://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/lib3ds/lib3ds-1.3.0.zip)
+		download_and_unzip(
+			LINK ${LIB3DS_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "Lib3DS")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- Lib3DS - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- lib3ds - using downloaded source")
-	add_library(
-		external-lib3ds SHARED
-		"${LIB3DS_DIR}/lib3ds/atmosphere.c"
-		"${LIB3DS_DIR}/lib3ds/atmosphere.h"
-		"${LIB3DS_DIR}/lib3ds/background.c"
-		"${LIB3DS_DIR}/lib3ds/background.h"
-		"${LIB3DS_DIR}/lib3ds/camera.c"
-		"${LIB3DS_DIR}/lib3ds/camera.h"
-		"${LIB3DS_DIR}/lib3ds/chunk.c"
-		"${LIB3DS_DIR}/lib3ds/chunk.h"
-		"${LIB3DS_DIR}/lib3ds/chunktable.h"
-		"${LIB3DS_DIR}/lib3ds/ease.c"
-		"${LIB3DS_DIR}/lib3ds/ease.h"
-		"${LIB3DS_DIR}/lib3ds/file.c"
-		"${LIB3DS_DIR}/lib3ds/file.h"
-		"${LIB3DS_DIR}/lib3ds/io.c"
-		"${LIB3DS_DIR}/lib3ds/io.h"
-		"${LIB3DS_DIR}/lib3ds/light.c"
-		"${LIB3DS_DIR}/lib3ds/light.h"
-		"${LIB3DS_DIR}/lib3ds/material.c"
-		"${LIB3DS_DIR}/lib3ds/material.h"
-		"${LIB3DS_DIR}/lib3ds/matrix.c"
-		"${LIB3DS_DIR}/lib3ds/matrix.h"
-		"${LIB3DS_DIR}/lib3ds/mesh.c"
-		"${LIB3DS_DIR}/lib3ds/mesh.h"
-		"${LIB3DS_DIR}/lib3ds/node.c"
-		"${LIB3DS_DIR}/lib3ds/node.h"
-		"${LIB3DS_DIR}/lib3ds/quat.c"
-		"${LIB3DS_DIR}/lib3ds/quat.h"
-		"${LIB3DS_DIR}/lib3ds/shadow.c"
-		"${LIB3DS_DIR}/lib3ds/shadow.h"
-		"${LIB3DS_DIR}/lib3ds/tcb.c"
-		"${LIB3DS_DIR}/lib3ds/tcb.h"
-		"${LIB3DS_DIR}/lib3ds/tracks.c"
-		"${LIB3DS_DIR}/lib3ds/tracks.h"
-		"${LIB3DS_DIR}/lib3ds/types.h"
-		"${LIB3DS_DIR}/lib3ds/vector.c"
-		"${LIB3DS_DIR}/lib3ds/vector.h"
-		"${LIB3DS_DIR}/lib3ds/viewport.c"
-		"${LIB3DS_DIR}/lib3ds/viewport.h")
+	if (EXISTS ${LIB3DS_CHECK})
+		message(STATUS "- lib3ds - using downloaded source")
+		add_library(
+			external-lib3ds SHARED
+			"${LIB3DS_DIR}/lib3ds/atmosphere.c"
+			"${LIB3DS_DIR}/lib3ds/atmosphere.h"
+			"${LIB3DS_DIR}/lib3ds/background.c"
+			"${LIB3DS_DIR}/lib3ds/background.h"
+			"${LIB3DS_DIR}/lib3ds/camera.c"
+			"${LIB3DS_DIR}/lib3ds/camera.h"
+			"${LIB3DS_DIR}/lib3ds/chunk.c"
+			"${LIB3DS_DIR}/lib3ds/chunk.h"
+			"${LIB3DS_DIR}/lib3ds/chunktable.h"
+			"${LIB3DS_DIR}/lib3ds/ease.c"
+			"${LIB3DS_DIR}/lib3ds/ease.h"
+			"${LIB3DS_DIR}/lib3ds/file.c"
+			"${LIB3DS_DIR}/lib3ds/file.h"
+			"${LIB3DS_DIR}/lib3ds/io.c"
+			"${LIB3DS_DIR}/lib3ds/io.h"
+			"${LIB3DS_DIR}/lib3ds/light.c"
+			"${LIB3DS_DIR}/lib3ds/light.h"
+			"${LIB3DS_DIR}/lib3ds/material.c"
+			"${LIB3DS_DIR}/lib3ds/material.h"
+			"${LIB3DS_DIR}/lib3ds/matrix.c"
+			"${LIB3DS_DIR}/lib3ds/matrix.h"
+			"${LIB3DS_DIR}/lib3ds/mesh.c"
+			"${LIB3DS_DIR}/lib3ds/mesh.h"
+			"${LIB3DS_DIR}/lib3ds/node.c"
+			"${LIB3DS_DIR}/lib3ds/node.h"
+			"${LIB3DS_DIR}/lib3ds/quat.c"
+			"${LIB3DS_DIR}/lib3ds/quat.h"
+			"${LIB3DS_DIR}/lib3ds/shadow.c"
+			"${LIB3DS_DIR}/lib3ds/shadow.h"
+			"${LIB3DS_DIR}/lib3ds/tcb.c"
+			"${LIB3DS_DIR}/lib3ds/tcb.h"
+			"${LIB3DS_DIR}/lib3ds/tracks.c"
+			"${LIB3DS_DIR}/lib3ds/tracks.h"
+			"${LIB3DS_DIR}/lib3ds/types.h"
+			"${LIB3DS_DIR}/lib3ds/vector.c"
+			"${LIB3DS_DIR}/lib3ds/vector.h"
+			"${LIB3DS_DIR}/lib3ds/viewport.c"
+			"${LIB3DS_DIR}/lib3ds/viewport.h")
 
-	target_include_directories(external-lib3ds SYSTEM PUBLIC "${LIB3DS_DIR}")
-	target_link_libraries(external-lib3ds PRIVATE external-disable-warnings)
-	install(TARGETS external-lib3ds DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+		target_include_directories(external-lib3ds SYSTEM PUBLIC "${LIB3DS_DIR}")
+		target_link_libraries(external-lib3ds PRIVATE external-disable-warnings)
+		install(TARGETS external-lib3ds DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+	endif()
 endif()
diff --git a/src/external/libigl.cmake b/src/external/libigl.cmake
index 6c50b274e..0d9bc58ed 100644
--- a/src/external/libigl.cmake
+++ b/src/external/libigl.cmake
@@ -5,14 +5,23 @@
 option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIBIGL "Allow download and use of LibIGL source" ON)
 
 if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIBIGL)
-	set(LIBIGL_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/libigl-2.4.0)
+	set(LIBIGL_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/libigl-2.4.0")
+	set(LIBIGL_CHECK "${LIBIGL_DIR}/include/igl/igl_inline.h")
 
-	if (NOT EXISTS "${LIBIGL_DIR}/include/igl/igl_inline.h")
+	if (NOT EXISTS ${LIBIGL_CHECK})
 		set(LIBIGL_LINK https://github.com/libigl/libigl/archive/refs/tags/v2.4.0.zip)
-		download_and_unzip(${LIBIGL_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "LibIGL")
+		download_and_unzip(
+			LINK ${LIBIGL_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "LibIGL")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- LibIGL - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- libigl - using downloaded source")
-	add_library(external-libigl INTERFACE)
-	target_include_directories(external-libigl INTERFACE "${LIBIGL_DIR}/include/")
+	if (EXISTS ${LIBIGL_CHECK})
+		message(STATUS "- libigl - using downloaded source")
+		add_library(external-libigl INTERFACE)
+		target_include_directories(external-libigl INTERFACE "${LIBIGL_DIR}/include/")
+	endif()
 endif()
diff --git a/src/external/muparser.cmake b/src/external/muparser.cmake
index d4f945c8e..d5672b0c9 100644
--- a/src/external/muparser.cmake
+++ b/src/external/muparser.cmake
@@ -12,23 +12,31 @@ if(MESHLAB_ALLOW_SYSTEM_MUPARSER AND TARGET muparser::muparser)
 	add_library(external-muparser INTERFACE)
 	target_link_libraries(external-muparser INTERFACE muparser::muparser)
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_MUPARSER)
-	set(MUPARSER_VER 2.3.3-1)
-	set(MUPARSER_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/muparser-${MUPARSER_VER})
+	set(MUPARSER_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/muparser-2.3.3-1")
+	set(MUPARSER_CHECK "${MUPARSER_DIR}/src/muParser.cpp")
 
-	if (NOT EXISTS "${MUPARSER_DIR}/src/muParser.cpp")
-		set(MUPARSER_LINK https://github.com/beltoforion/muparser/archive/refs/tags/v${MUPARSER_VER}.zip)
-		download_and_unzip(${MUPARSER_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "muparser")
+	if (NOT EXISTS ${MUPARSER_CHECK})
+		set(MUPARSER_LINK https://github.com/beltoforion/muparser/archive/refs/tags/v2.3.3-1.zip)
+		download_and_unzip(
+			LINK ${MUPARSER_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "muparser")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- muparser - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- muparser - using downloaded source")
+	if (EXISTS ${MUPARSER_CHECK})
+		message(STATUS "- muparser - using downloaded source")
 
-	set(ENABLE_SAMPLES OFF)
-	set(MESSAGE_QUIET ON)
-	add_subdirectory(${MUPARSER_DIR})
-	unset(MESSAGE_QUIET)
-	unset(ENABLE_SAMPLES)
+		set(ENABLE_SAMPLES OFF)
+		set(MESSAGE_QUIET ON)
+		add_subdirectory(${MUPARSER_DIR})
+		unset(MESSAGE_QUIET)
+		unset(ENABLE_SAMPLES)
 
-	add_library(external-muparser INTERFACE)
-	target_link_libraries(external-muparser INTERFACE muparser)
-	install(TARGETS muparser DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+		add_library(external-muparser INTERFACE)
+		target_link_libraries(external-muparser INTERFACE muparser)
+		install(TARGETS muparser DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+	endif()
 endif()
diff --git a/src/external/nexus.cmake b/src/external/nexus.cmake
index d8bccf0aa..baded8450 100644
--- a/src/external/nexus.cmake
+++ b/src/external/nexus.cmake
@@ -6,27 +6,44 @@ option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS "Allow download and use of nexus sour
 
 if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS)
 	# todo - make release of nexus and corto
-	set(NEXUS_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/nexus-master)
-	set(CORTO_DIR ${NEXUS_DIR}/src/corto)
+	set(NEXUS_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/nexus-master")
+	set(NEXUS_CHECK "${NEXUS_DIR}/CMakeLists.txt")
+	set(CORTO_DIR "${NEXUS_DIR}/src/corto")
+	set(CORTO_CHECK "${CORTO_DIR}/CMakeLists.txt")
 
-	if (NOT EXISTS "${NEXUS_DIR}/CMakeLists.txt")
+	if (NOT EXISTS ${NEXUS_CHECK})
 		set(NEXUS_LINK https://github.com/cnr-isti-vclab/nexus/archive/refs/heads/master.zip)
-		download_and_unzip(${NEXUS_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "nexus")
+		download_and_unzip(
+			LINK ${NEXUS_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "nexus")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- nexus - download failed.")
+		endif()
 	endif()
 
-	if (NOT EXISTS "${CORTO_DIR}/CMakeLists.txt")
+	if (NOT EXISTS ${CORTO_CHECK})
 		file(REMOVE_RECURSE ${NEXUS_DIR}/src/corto)
 		set(CORTO_LINK https://github.com/cnr-isti-vclab/corto/archive/refs/heads/master.zip)
-		download_and_unzip(${CORTO_LINK} "${NEXUS_DIR}/src/" "corto")
-		file(RENAME ${NEXUS_DIR}/src/corto-master ${NEXUS_DIR}/src/corto)
+		download_and_unzip(
+			LINK ${CORTO_LINK}
+			DIR "${NEXUS_DIR}/src/"
+			NAME "corto")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- corto - download failed.")
+		else()
+			file(RENAME ${NEXUS_DIR}/src/corto-master ${NEXUS_DIR}/src/corto)
+		endif()
 	endif()
 
-	message(STATUS "- nexus - using downloaded source")
+	if (EXISTS ${NEXUS_CHECK} AND EXISTS ${CORTO_CHECK})
+		message(STATUS "- nexus - using downloaded source")
 
-	set (BUILD_NXS_BUILD OFF)
-	set (BUILD_NXS_EDIT OFF)
-	set (BUILD_NXS_VIEW OFF)
-	add_subdirectory(${NEXUS_DIR} EXCLUDE_FROM_ALL)
-	add_library(external-nexus INTERFACE)
-	target_link_libraries(external-nexus INTERFACE nexus)
+		set (BUILD_NXS_BUILD OFF)
+		set (BUILD_NXS_EDIT OFF)
+		set (BUILD_NXS_VIEW OFF)
+		add_subdirectory(${NEXUS_DIR} EXCLUDE_FROM_ALL)
+		add_library(external-nexus INTERFACE)
+		target_link_libraries(external-nexus INTERFACE nexus)
+	endif()
 endif()
diff --git a/src/external/openctm.cmake b/src/external/openctm.cmake
index 041563dae..abe51f5f2 100644
--- a/src/external/openctm.cmake
+++ b/src/external/openctm.cmake
@@ -12,33 +12,42 @@ if(MESHLAB_ALLOW_SYSTEM_OPENCTM AND TARGET OpenCTM::OpenCTM)
 	add_library(external-openctm INTERFACE)
 	target_link_libraries(external-openctm INTERFACE OpenCTM::OpenCTM)
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_OPENCTM)
-	set(OPENCTM_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/OpenCTM-1.0.3)
+	set(OPENCTM_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/OpenCTM-1.0.3")
+	set(OPENCTM_CHECK "${OPENCTM_DIR}/lib/openctm.c")
 
-	if (NOT EXISTS "${OPENCTM_DIR}/lib/openctm.c")
+	if (NOT EXISTS ${OPENCTM_CHECK})
 		set(OPENCTM_LINK https://sourceforge.net/projects/openctm/files/OpenCTM-1.0.3/OpenCTM-1.0.3-src.zip/download)
-		download_and_unzip(${OPENCTM_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "OpenCTM")
+		download_and_unzip(
+			LINK ${OPENCTM_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "OpenCTM")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- OpenCTM - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- OpenCTM - using downloaded source")
-	add_library(
-		external-openctm STATIC
-		"${OPENCTM_DIR}/lib/openctm.c"
-		"${OPENCTM_DIR}/lib/stream.c"
-		"${OPENCTM_DIR}/lib/compressRAW.c"
-		"${OPENCTM_DIR}/lib/compressMG1.c"
-		"${OPENCTM_DIR}/lib/compressMG2.c"
-		"${OPENCTM_DIR}/lib/liblzma/Alloc.c"
-		"${OPENCTM_DIR}/lib/liblzma/LzFind.c"
-		"${OPENCTM_DIR}/lib/liblzma/LzmaDec.c"
-		"${OPENCTM_DIR}/lib/liblzma/LzmaEnc.c"
-		"${OPENCTM_DIR}/lib/liblzma/LzmaLib.c")
-	target_compile_definitions(external-openctm PUBLIC OPENCTM_STATIC)
-	target_include_directories(
-		external-openctm SYSTEM
-		PUBLIC "${OPENCTM_DIR}/lib" SYSTEM
-		PRIVATE "${OPENCTM_DIR}/lib/liblzma")
-	if(MSVC)
-		target_compile_definitions(external-openctm PRIVATE _CRT_SECURE_NO_WARNINGS)
+	if (EXISTS ${OPENCTM_CHECK})
+		message(STATUS "- OpenCTM - using downloaded source")
+		add_library(
+			external-openctm STATIC
+			"${OPENCTM_DIR}/lib/openctm.c"
+			"${OPENCTM_DIR}/lib/stream.c"
+			"${OPENCTM_DIR}/lib/compressRAW.c"
+			"${OPENCTM_DIR}/lib/compressMG1.c"
+			"${OPENCTM_DIR}/lib/compressMG2.c"
+			"${OPENCTM_DIR}/lib/liblzma/Alloc.c"
+			"${OPENCTM_DIR}/lib/liblzma/LzFind.c"
+			"${OPENCTM_DIR}/lib/liblzma/LzmaDec.c"
+			"${OPENCTM_DIR}/lib/liblzma/LzmaEnc.c"
+			"${OPENCTM_DIR}/lib/liblzma/LzmaLib.c")
+		target_compile_definitions(external-openctm PUBLIC OPENCTM_STATIC)
+		target_include_directories(
+			external-openctm SYSTEM
+			PUBLIC "${OPENCTM_DIR}/lib" SYSTEM
+			PRIVATE "${OPENCTM_DIR}/lib/liblzma")
+		if(MSVC)
+			target_compile_definitions(external-openctm PRIVATE _CRT_SECURE_NO_WARNINGS)
+		endif()
+		target_link_libraries(external-openctm PRIVATE external-disable-warnings)
 	endif()
-	target_link_libraries(external-openctm PRIVATE external-disable-warnings)
 endif()
diff --git a/src/external/qhull.cmake b/src/external/qhull.cmake
index 23a002497..2e11f8ed4 100644
--- a/src/external/qhull.cmake
+++ b/src/external/qhull.cmake
@@ -12,21 +12,29 @@ if(MESHLAB_ALLOW_SYSTEM_QHULL AND TARGET Qhull::qhull_r)
 	add_library(external-qhull INTERFACE)
 	target_link_libraries(external-qhull INTERFACE Qhull::qhull_r)
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_QHULL)
-	set(QHULL_VER 2020.2)
-	set(QHULL_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/qhull-${QHULL_VER})
+	set(QHULL_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/qhull-2020.2")
+	set(QHULL_CHECK "${QHULL_DIR}/src/libqhull_r/libqhull_r.h")
 
-	if (NOT EXISTS "${QHULL_DIR}/src/libqhull_r/libqhull_r.h")
-		set(QHULL_LINK https://github.com/qhull/qhull/archive/refs/tags/${QHULL_VER}.zip)
-		download_and_unzip(${QHULL_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "Qhull")
+	if (NOT EXISTS ${QHULL_CHECK})
+		set(QHULL_LINK https://github.com/qhull/qhull/archive/refs/tags/2020.2.zip)
+		download_and_unzip(
+			LINK ${QHULL_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "Qhull")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- Qhull - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- qhull - using downloaded source")
+	if (EXISTS ${QHULL_CHECK})
+		message(STATUS "- qhull - using downloaded source")
 
-	set(MESSAGE_QUIET ON)
-	add_subdirectory(${QHULL_DIR} EXCLUDE_FROM_ALL)
-	unset(MESSAGE_QUIET)
+		set(MESSAGE_QUIET ON)
+		add_subdirectory(${QHULL_DIR} EXCLUDE_FROM_ALL)
+		unset(MESSAGE_QUIET)
 
-	add_library(external-qhull INTERFACE)
-	target_link_libraries(external-qhull INTERFACE qhullstatic_r)
-	target_include_directories(external-qhull INTERFACE "${QHULL_DIR}/src")
+		add_library(external-qhull INTERFACE)
+		target_link_libraries(external-qhull INTERFACE qhullstatic_r)
+		target_include_directories(external-qhull INTERFACE "${QHULL_DIR}/src")
+	endif()
 endif()
diff --git a/src/external/ssynth.cmake b/src/external/ssynth.cmake
index 3c782e564..a27207f14 100644
--- a/src/external/ssynth.cmake
+++ b/src/external/ssynth.cmake
@@ -2,20 +2,28 @@
 # Copyright 2019, 2020, Visual Computing Lab, ISTI - Italian National Research Council
 # SPDX-License-Identifier: BSL-1.0
 
-option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_STRUCTURE_SYNTH "Allow use of bundled structure-synth source" ON)
+option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_STRUCTURE_SYNTH "Allow use of bundled Structure Synth source" ON)
 
 if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_STRUCTURE_SYNTH)
-	set(SSYNTH_VER 1.5.1)
-	set(SSYNTH_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/StructureSynth-${SSYNTH_VER})
+	set(SSYNTH_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/StructureSynth-1.5.1")
+	set(SSYNTH_CHECK "${SSYNTH_DIR}/StructureSynth/Model/Action.h")
 
-	if (NOT EXISTS "${SSYNTH_DIR}/StructureSynth/Model/Action.h")
-		set(SSYNTH_LINK "https://github.com/alemuntoni/StructureSynth/archive/refs/tags/${SSYNTH_VER}.zip")
-		download_and_unzip(${SSYNTH_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "Structure Synth")
+	if (NOT EXISTS ${SSYNTH_CHECK})
+		set(SSYNTH_LINK "https://github.com/alemuntoni/StructureSynth/archive/refs/tags/1.5.1.zip")
+		download_and_unzip(
+			LINK ${SSYNTH_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "Structure Synth")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- Structure Synth - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- structure-synth - using downloaded source")
+	if(EXISTS ${SSYNTH_CHECK})
+		message(STATUS "- Structure Synth - using downloaded source")
 
-	add_subdirectory(${SSYNTH_DIR})
-	add_library(external-ssynth INTERFACE)
-	target_link_libraries(external-ssynth INTERFACE structure-synth)
+		add_subdirectory(${SSYNTH_DIR})
+		add_library(external-ssynth INTERFACE)
+		target_link_libraries(external-ssynth INTERFACE structure-synth)
+	endif()
 endif()
diff --git a/src/external/tinygltf.cmake b/src/external/tinygltf.cmake
index 691ca19e0..d04bc99be 100644
--- a/src/external/tinygltf.cmake
+++ b/src/external/tinygltf.cmake
@@ -5,14 +5,23 @@
 option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_TINYGLTF "Allow download and use of tinyglTF source" ON)
 
 if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_TINYGLTF)
-	set(TINYGLTF_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/tinygltf-2.6.3)
+	set(TINYGLTF_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/tinygltf-2.6.3")
+	set(TINYGLTF_CHECK "${TINYGLTF_DIR}/tiny_gltf.h")
 
-	if (NOT EXISTS "${TINYGLTF_DIR}/tiny_gltf.h")
+	if (NOT EXISTS ${TINYGLTF_CHECK})
 		set(TINYGLTF_LINK https://github.com/syoyo/tinygltf/archive/refs/tags/v2.6.3.zip)
-		download_and_unzip(${TINYGLTF_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "tinygltf")
+		download_and_unzip(
+			LINK ${TINYGLTF_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "tinygltf")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- tinygltf - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- tiny glTF - using downloaded source")
-	add_library(external-tinygltf INTERFACE)
-	target_include_directories(external-tinygltf INTERFACE ${TINYGLTF_DIR})
+	if(EXISTS ${TINYGLTF_CHECK})
+		message(STATUS "- tiny glTF - using downloaded source")
+		add_library(external-tinygltf INTERFACE)
+		target_include_directories(external-tinygltf INTERFACE ${TINYGLTF_DIR})
+	endif()
 endif()
diff --git a/src/external/u3d.cmake b/src/external/u3d.cmake
index 25beee54e..c9037d5f6 100644
--- a/src/external/u3d.cmake
+++ b/src/external/u3d.cmake
@@ -6,24 +6,33 @@ option(MESHLAB_ALLOW_DOWNLOAD_SOURCE_U3D "Allow download and use of u3d source"
 
 if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_U3D)
 	# todo - make release of u3d
-	set(U3D_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/u3d-master)
+	set(U3D_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/u3d-master")
+	set(U3D_CHECK "${U3D_DIR}/CMakeLists.txt")
 
-	if (NOT EXISTS ${U3D_DIR}/CMakeLists.txt)
+	if (NOT EXISTS ${U3D_CHECK})
 		set(U3D_LINK https://github.com/alemuntoni/u3d/archive/refs/heads/master.zip)
-		download_and_unzip(${U3D_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "u3d")
+		download_and_unzip(
+			LINK ${U3D_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "u3d")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- u3d - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- u3d - using bundled source")
+	if (EXISTS ${U3D_CHECK})
+		message(STATUS "- u3d - using bundled source")
 
-	set(MESSAGE_QUIET ON)
-	add_subdirectory(${U3D_DIR})
-	unset(MESSAGE_QUIET)
-	install(
-		TARGETS
-			IFXCore
-			IFXExporting
-			IFXScheduling
-			IDTF-to-U3D-converter
-		DESTINATION
-			${MESHLAB_LIB_INSTALL_DIR})
+		set(MESSAGE_QUIET ON)
+		add_subdirectory(${U3D_DIR})
+		unset(MESSAGE_QUIET)
+		install(
+			TARGETS
+				IFXCore
+				IFXExporting
+				IFXScheduling
+				IDTF-to-U3D-converter
+			DESTINATION
+				${MESHLAB_LIB_INSTALL_DIR})
+	endif()
 endif()
diff --git a/src/external/xerces.cmake b/src/external/xerces.cmake
index 59df3092a..c170d4cdf 100644
--- a/src/external/xerces.cmake
+++ b/src/external/xerces.cmake
@@ -7,33 +7,40 @@ option(MESHLAB_ALLOW_SYSTEM_XERCES "Allow use of system-provided Xerces-C" ON)
 
 find_package(XercesC)
 
-# https://dlcdn.apache.org//xerces/c/3/sources/xerces-c-3.2.4.zip
-
 if(MESHLAB_ALLOW_SYSTEM_XERCES AND TARGET XercesC::XercesC)
-	message(STATUS "- XercesC - using system-provided library")
+	message(STATUS "- Xerces-C - using system-provided library")
 	add_library(external-xerces INTERFACE)
 	target_link_libraries(external-xerces INTERFACE XercesC::XercesC)
 elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_XERCES)
 	set(XERCES_C_VER 3.2.4)
-	set(XERCES_C_DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/xerces-c-${XERCES_C_VER})
+	set(XERCES_C_DIR "${MESHLAB_EXTERNAL_DOWNLOAD_DIR}/xerces-c-${XERCES_C_VER}")
+	set(XERCES_C_CHECK "${XERCES_C_DIR}/CMakeLists.txt")
 
-	if (NOT EXISTS ${XERCES_C_DIR}/CMakeLists.txt)
+	if(NOT EXISTS ${XERCES_C_CHECK})
 		set(XERCES_C_LINK https://dlcdn.apache.org//xerces/c/3/sources/xerces-c-${XERCES_C_VER}.zip)
-		download_and_unzip(${XERCES_C_LINK} ${MESHLAB_EXTERNAL_DOWNLOAD_DIR} "Xerces-C")
+		download_and_unzip(
+			LINK ${XERCES_C_LINK}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
+			NAME "Xerces-C")
+		if (NOT download_and_unzip_SUCCESS)
+			message(STATUS "- Xerces-C - download failed.")
+		endif()
 	endif()
 
-	message(STATUS "- XercesC - using downloaded source")
+	if(EXISTS ${XERCES_C_CHECK})
+		message(STATUS "- Xerces-C - using downloaded source")
 
-	set(MESSAGE_QUIET ON)
-	add_subdirectory(${XERCES_C_DIR} EXCLUDE_FROM_ALL)
-	unset(MESSAGE_QUIET)
+		set(MESSAGE_QUIET ON)
+		add_subdirectory(${XERCES_C_DIR} EXCLUDE_FROM_ALL)
+		unset(MESSAGE_QUIET)
 
-	add_library(external-xerces INTERFACE)
-	target_link_libraries(external-xerces INTERFACE xerces-c)
-	target_include_directories(
-		external-xerces INTERFACE
-		${XERCES_C_DIR}/src
-		${MESHLAB_EXTERNAL_BINARY_DIR}/xerces-c-${XERCES_C_VER}/src)
-	add_library(XercesC::XercesC ALIAS external-xerces)
-	install(TARGETS xerces-c DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+		add_library(external-xerces INTERFACE)
+		target_link_libraries(external-xerces INTERFACE xerces-c)
+		target_include_directories(
+			external-xerces INTERFACE
+			${XERCES_C_DIR}/src
+			${MESHLAB_EXTERNAL_BINARY_DIR}/xerces-c-${XERCES_C_VER}/src)
+		add_library(XercesC::XercesC ALIAS external-xerces)
+		install(TARGETS xerces-c DESTINATION ${MESHLAB_LIB_INSTALL_DIR})
+	endif()
 endif()

From d46e466c9db715fd33cf2f366b3ef959a9812c9d Mon Sep 17 00:00:00 2001
From: alemuntoni <muntoni.alessandro@gmail.com>
Date: Fri, 4 Nov 2022 15:43:43 +0100
Subject: [PATCH 3/4] using md5 when downloading external libraries

---
 src/cmake/meshlab_tools.cmake | 34 +++++++++++++++++++++++++---------
 src/external/boost.cmake      |  6 ++++--
 src/external/cgal.cmake       | 12 ++++++++----
 src/external/e57.cmake        |  6 ++++--
 src/external/easyexif.cmake   |  6 ++++--
 src/external/glew.cmake       |  6 ++++--
 src/external/levmar.cmake     |  6 ++++--
 src/external/lib3ds.cmake     |  6 ++++--
 src/external/libigl.cmake     |  6 ++++--
 src/external/muparser.cmake   |  6 ++++--
 src/external/nexus.cmake      | 12 ++++++++----
 src/external/openctm.cmake    |  6 ++++--
 src/external/qhull.cmake      |  6 ++++--
 src/external/ssynth.cmake     |  8 +++++---
 src/external/tinygltf.cmake   |  6 ++++--
 src/external/u3d.cmake        |  6 ++++--
 src/external/xerces.cmake     |  6 ++++--
 17 files changed, 98 insertions(+), 46 deletions(-)

diff --git a/src/cmake/meshlab_tools.cmake b/src/cmake/meshlab_tools.cmake
index 9e2c0f77b..626b39981 100644
--- a/src/cmake/meshlab_tools.cmake
+++ b/src/cmake/meshlab_tools.cmake
@@ -38,7 +38,7 @@ endfunction()
 function(download_and_unzip)
 	set(download_and_unzip_SUCCESS FALSE PARENT_SCOPE)
 	set(options)
-	set(oneValueArgs SHA NAME DIR)
+	set(oneValueArgs MD5 NAME DIR)
 	set(multiValueArgs LINK)
 	cmake_parse_arguments(DAU
 		"${options}" "${oneValueArgs}"
@@ -55,14 +55,30 @@ function(download_and_unzip)
 		message(STATUS "Downloading ${DAU_NAME} from ${LINK}")
 
 		file(DOWNLOAD ${LINK} ${ZIP})
-		message(STATUS "${DAU_NAME} downloaded.")
-		message(STATUS "Extracting ${DAU_NAME} archive...")
-		file(ARCHIVE_EXTRACT
-			INPUT ${ZIP}
-			DESTINATION ${DAU_DIR})
-		message(STATUS "${DAU_NAME} archive extracted.")
-		file(REMOVE ${ZIP})
-		set(download_and_unzip_SUCCESS TRUE PARENT_SCOPE)
+
+		file(MD5 ${ZIP} MD5SUM)
+
+		# no md5 argument given, no checksum needed...
+		if (NOT DEFINED DAU_MD5)
+			set(DAU_MD5 ${MD5SUM})
+		endif()
+
+		# manual md5 check, avoid to fail when a download fails
+		if(MD5SUM STREQUAL ${DAU_MD5}) # download successful
+			message(STATUS "${DAU_NAME} downloaded.")
+			message(STATUS "Extracting ${DAU_NAME} archive...")
+			file(ARCHIVE_EXTRACT
+				INPUT ${ZIP}
+				DESTINATION ${DAU_DIR})
+			message(STATUS "${DAU_NAME} archive extracted.")
+			file(REMOVE ${ZIP})
+			set(download_and_unzip_SUCCESS TRUE PARENT_SCOPE)
+			break() # done
+		else()
+			file(REMOVE ${ZIP})
+			message(STATUS "${DAU_NAME} download failed...")
+			# next link in DAU_LINK list...
+		endif()
 	endforeach()
 endfunction()
 
diff --git a/src/external/boost.cmake b/src/external/boost.cmake
index 46ea6fa20..7187dd305 100644
--- a/src/external/boost.cmake
+++ b/src/external/boost.cmake
@@ -20,10 +20,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_BOOST)
 
 	if (NOT EXISTS ${BOOST_CHECK})
 		set(BOOST_LINK https://boostorg.jfrog.io/artifactory/main/release/1.75.0/source/boost_1_75_0.zip)
+		set(BOOST_MD5 d3b276f6d22246171f93282910a1d583)
 		download_and_unzip(
+			NAME "Boost"
+			MD5 ${BOOST_MD5}
 			LINK ${BOOST_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "Boost")
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- Boost - download failed.")
 		endif()
diff --git a/src/external/cgal.cmake b/src/external/cgal.cmake
index ddeb7a2c0..3552a08ad 100644
--- a/src/external/cgal.cmake
+++ b/src/external/cgal.cmake
@@ -21,10 +21,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_CGAL)
 
 	if (NOT EXISTS ${CGAL_CHECK})
 		set(CGAL_LINK https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1.zip)
+		set(CGAL_MD5 1a999ab90ea4cf28f6aa17ea2af24876)
 		download_and_unzip(
+			NAME "CGAL"
 			LINK ${CGAL_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "CGAL")
+			MD5 ${CGAL_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- CGAL - download failed.")
 			set(CGAL_DOWNLOAD_SUCCESS FALSE)
@@ -33,10 +35,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_CGAL)
 
 	if (WIN32 AND NOT EXISTS ${CGAL_WIN_CHECK})
 		set(CGAL_AUX_LINK https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1-win64-auxiliary-libraries-gmp-mpfr.zip)
+		set(CGAL_AUX_MD5 247f4dca741c6b9a9be76286414070fa)
 		download_and_unzip(
+			NAME "CGAL auxiliary libraries"
 			LINK ${CGAL_AUX_LINK}
-			DIR ${CGAL_DIR}
-			NAME "CGAL auxiliary libraries")
+			MD5 ${CGAL_AUX_MD5}
+			DIR ${CGAL_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- CGAL auxiliary libraries - download failed.")
 			set(CGAL_DOWNLOAD_SUCCESS FALSE)
diff --git a/src/external/e57.cmake b/src/external/e57.cmake
index af27fae05..867b26a7b 100644
--- a/src/external/e57.cmake
+++ b/src/external/e57.cmake
@@ -11,10 +11,12 @@ if (TARGET XercesC::XercesC)
 
 		if (NOT EXISTS ${LIBE57_CHECK})
 			set(LIBE57_LINK https://github.com/asmaloney/libE57Format/archive/refs/tags/v2.3.0.zip)
+			set(LIBE57_MD5 958ada3883f9b60195f79bbab156f3e3)
 			download_and_unzip(
+				NAME "LibE57"
+				MD5 ${LIBE57_MD5}
 				LINK ${LIBE57_LINK}
-				DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-				NAME "LibE57")
+				DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 			if (NOT download_and_unzip_SUCCESS)
 				message(STATUS "- LibE57 - download failed.")
 			endif()
diff --git a/src/external/easyexif.cmake b/src/external/easyexif.cmake
index ce18b8053..d6f19b9ca 100644
--- a/src/external/easyexif.cmake
+++ b/src/external/easyexif.cmake
@@ -10,10 +10,12 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_EASYEXIF)
 
 	if (NOT EXISTS ${EASYEXIF_CHECK})
 		set(EASYEXIF_LINK https://github.com/mayanklahiri/easyexif/archive/refs/tags/v1.0.zip)
+		set(EASYEXIF_MD5 d46ec21b5c8ce13cda0fe66a4477a8c3)
 		download_and_unzip(
+			NAME "EasyExif"
 			LINK ${EASYEXIF_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "EasyExif")
+			MD5 ${EASYEXIF_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(FATAL_ERROR "- EasyExif - download failed.")
 		endif()
diff --git a/src/external/glew.cmake b/src/external/glew.cmake
index a304e0632..fff07871f 100644
--- a/src/external/glew.cmake
+++ b/src/external/glew.cmake
@@ -29,10 +29,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_GLEW)
 
 	if (NOT EXISTS ${GLEW_CHECK})
 		set(GLEW_LINK https://github.com/nigels-com/glew/releases/download/glew-2.2.0/glew-2.2.0.zip)
+		set(GLEW_MD5 970535b75b1b69ebd018a0fa05af63d1)
 		download_and_unzip(
+			NAME "GLEW"
 			LINK ${GLEW_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "GLEW")
+			MD5 ${GLEW_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(FATAL_ERROR "- GLEW - download failed.")
 		endif()
diff --git a/src/external/levmar.cmake b/src/external/levmar.cmake
index 57ebb8648..fb5de25db 100644
--- a/src/external/levmar.cmake
+++ b/src/external/levmar.cmake
@@ -10,10 +10,12 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LEVMAR)
 
 	if (NOT EXISTS ${LEVMAR_CHECK})
 		set(LEVMAR_LINK http://users.ics.forth.gr/~lourakis/levmar/levmar-2.6.tgz)
+		set(LEVMAR_MD5 16bc34efa1617219f241eef06427f13f)
 		download_and_unzip(
+			NAME "Levmar"
 			LINK ${LEVMAR_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "Levmar")
+			MD5 ${LEVMAR_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- Levmar - download failed.")
 		endif()
diff --git a/src/external/lib3ds.cmake b/src/external/lib3ds.cmake
index 5c03328e5..8d15dd076 100644
--- a/src/external/lib3ds.cmake
+++ b/src/external/lib3ds.cmake
@@ -18,10 +18,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIB3DS)
 
 	if (NOT EXISTS ${LIB3DS_CHECK})
 		set(LIB3DS_LINK http://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/lib3ds/lib3ds-1.3.0.zip)
+		set(LIB3DS_MD5 2572f7b0f29b591d494c1a0658b35c86)
 		download_and_unzip(
+			NAME "Lib3DS"
 			LINK ${LIB3DS_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "Lib3DS")
+			MD5 ${LIB3DS_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- Lib3DS - download failed.")
 		endif()
diff --git a/src/external/libigl.cmake b/src/external/libigl.cmake
index 0d9bc58ed..6554993c7 100644
--- a/src/external/libigl.cmake
+++ b/src/external/libigl.cmake
@@ -10,10 +10,12 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIBIGL)
 
 	if (NOT EXISTS ${LIBIGL_CHECK})
 		set(LIBIGL_LINK https://github.com/libigl/libigl/archive/refs/tags/v2.4.0.zip)
+		set(LIBIGL_MD5 0b4fea5dba2117b8db85c99a39a71f83)
 		download_and_unzip(
+			NAME "LibIGL"
 			LINK ${LIBIGL_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "LibIGL")
+			MD5 ${LIBIGL_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- LibIGL - download failed.")
 		endif()
diff --git a/src/external/muparser.cmake b/src/external/muparser.cmake
index d5672b0c9..ce33a7c0a 100644
--- a/src/external/muparser.cmake
+++ b/src/external/muparser.cmake
@@ -17,10 +17,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_MUPARSER)
 
 	if (NOT EXISTS ${MUPARSER_CHECK})
 		set(MUPARSER_LINK https://github.com/beltoforion/muparser/archive/refs/tags/v2.3.3-1.zip)
+		set(MUPARSER_MD5 8cf887ce460a405b8d8b966e0d5c94e3)
 		download_and_unzip(
+			NAME "muparser"
 			LINK ${MUPARSER_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "muparser")
+			MD5 ${MUPARSER_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- muparser - download failed.")
 		endif()
diff --git a/src/external/nexus.cmake b/src/external/nexus.cmake
index baded8450..9b22cdfdb 100644
--- a/src/external/nexus.cmake
+++ b/src/external/nexus.cmake
@@ -13,10 +13,12 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS)
 
 	if (NOT EXISTS ${NEXUS_CHECK})
 		set(NEXUS_LINK https://github.com/cnr-isti-vclab/nexus/archive/refs/heads/master.zip)
+		#set(NEXUS_MD5 3e50878dbaedd140f3e8c34d5af9a9d9)
 		download_and_unzip(
+			NAME "nexus"
 			LINK ${NEXUS_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "nexus")
+			#MD5 ${NEXUS_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- nexus - download failed.")
 		endif()
@@ -25,10 +27,12 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS)
 	if (NOT EXISTS ${CORTO_CHECK})
 		file(REMOVE_RECURSE ${NEXUS_DIR}/src/corto)
 		set(CORTO_LINK https://github.com/cnr-isti-vclab/corto/archive/refs/heads/master.zip)
+		#set(CORTO_MD5 ede1b41e369a8117d8f2f46fba89e11d)
 		download_and_unzip(
+			NAME "corto"
 			LINK ${CORTO_LINK}
-			DIR "${NEXUS_DIR}/src/"
-			NAME "corto")
+			#MD5 ${CORTO_MD5}
+			DIR "${NEXUS_DIR}/src/")
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- corto - download failed.")
 		else()
diff --git a/src/external/openctm.cmake b/src/external/openctm.cmake
index abe51f5f2..b293ef51c 100644
--- a/src/external/openctm.cmake
+++ b/src/external/openctm.cmake
@@ -17,10 +17,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_OPENCTM)
 
 	if (NOT EXISTS ${OPENCTM_CHECK})
 		set(OPENCTM_LINK https://sourceforge.net/projects/openctm/files/OpenCTM-1.0.3/OpenCTM-1.0.3-src.zip/download)
+		set(OPENCTM_MD5 a87b6a6509ae0712b4a55f8887dc6a54)
 		download_and_unzip(
+			NAME "OpenCTM"
 			LINK ${OPENCTM_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "OpenCTM")
+			MD5 ${OPENCTM_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- OpenCTM - download failed.")
 		endif()
diff --git a/src/external/qhull.cmake b/src/external/qhull.cmake
index 2e11f8ed4..790116af4 100644
--- a/src/external/qhull.cmake
+++ b/src/external/qhull.cmake
@@ -17,10 +17,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_QHULL)
 
 	if (NOT EXISTS ${QHULL_CHECK})
 		set(QHULL_LINK https://github.com/qhull/qhull/archive/refs/tags/2020.2.zip)
+		set(QHULL_MD5 a0a9b0e69bdbd9461319b8d2ac3d2f2e)
 		download_and_unzip(
+			NAME "Qhull"
 			LINK ${QHULL_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "Qhull")
+			MD5 ${QHULL_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- Qhull - download failed.")
 		endif()
diff --git a/src/external/ssynth.cmake b/src/external/ssynth.cmake
index a27207f14..bf6375310 100644
--- a/src/external/ssynth.cmake
+++ b/src/external/ssynth.cmake
@@ -9,11 +9,13 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_STRUCTURE_SYNTH)
 	set(SSYNTH_CHECK "${SSYNTH_DIR}/StructureSynth/Model/Action.h")
 
 	if (NOT EXISTS ${SSYNTH_CHECK})
-		set(SSYNTH_LINK "https://github.com/alemuntoni/StructureSynth/archive/refs/tags/1.5.1.zip")
+		set(SSYNTH_LINK https://github.com/alemuntoni/StructureSynth/archive/refs/tags/1.5.1.zip)
+		set(SSYNTH_MD5 e2122c5e6e370fb36c885bccf59562b7)
 		download_and_unzip(
+			NAME "Structure Synth"
 			LINK ${SSYNTH_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "Structure Synth")
+			MD5 ${SSYNTH_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- Structure Synth - download failed.")
 		endif()
diff --git a/src/external/tinygltf.cmake b/src/external/tinygltf.cmake
index d04bc99be..4a53f774c 100644
--- a/src/external/tinygltf.cmake
+++ b/src/external/tinygltf.cmake
@@ -10,10 +10,12 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_TINYGLTF)
 
 	if (NOT EXISTS ${TINYGLTF_CHECK})
 		set(TINYGLTF_LINK https://github.com/syoyo/tinygltf/archive/refs/tags/v2.6.3.zip)
+		set(TINYGLTF_MD5 f63ab0fb59e5de059d9719cc14057dc8)
 		download_and_unzip(
+			NAME "tinygltf"
 			LINK ${TINYGLTF_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "tinygltf")
+			MD5 ${TINYGLTF_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- tinygltf - download failed.")
 		endif()
diff --git a/src/external/u3d.cmake b/src/external/u3d.cmake
index c9037d5f6..80c8a8874 100644
--- a/src/external/u3d.cmake
+++ b/src/external/u3d.cmake
@@ -11,10 +11,12 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_U3D)
 
 	if (NOT EXISTS ${U3D_CHECK})
 		set(U3D_LINK https://github.com/alemuntoni/u3d/archive/refs/heads/master.zip)
+		#set(U3D_MD5 3b15b2f75206ea24b8991333562aa9ca)
 		download_and_unzip(
+			NAME "u3d"
 			LINK ${U3D_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "u3d")
+			#MD5 ${U3D_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- u3d - download failed.")
 		endif()
diff --git a/src/external/xerces.cmake b/src/external/xerces.cmake
index c170d4cdf..fc94fd391 100644
--- a/src/external/xerces.cmake
+++ b/src/external/xerces.cmake
@@ -18,10 +18,12 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_XERCES)
 
 	if(NOT EXISTS ${XERCES_C_CHECK})
 		set(XERCES_C_LINK https://dlcdn.apache.org//xerces/c/3/sources/xerces-c-${XERCES_C_VER}.zip)
+		set(XERCES_C_MD5 f84488fc2b8f62c4afca2f9943a42c00)
 		download_and_unzip(
+			NAME "Xerces-C"
 			LINK ${XERCES_C_LINK}
-			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR}
-			NAME "Xerces-C")
+			MD5 ${XERCES_C_MD5}
+			DIR ${MESHLAB_EXTERNAL_DOWNLOAD_DIR})
 		if (NOT download_and_unzip_SUCCESS)
 			message(STATUS "- Xerces-C - download failed.")
 		endif()

From 026074d38a259abcb86d862e6fec27a6b2556584 Mon Sep 17 00:00:00 2001
From: alemuntoni <muntoni.alessandro@gmail.com>
Date: Fri, 4 Nov 2022 17:00:42 +0100
Subject: [PATCH 4/4] download external libraries mirror links

---
 src/external/cgal.cmake     | 8 ++++++--
 src/external/e57.cmake      | 4 +++-
 src/external/easyexif.cmake | 4 +++-
 src/external/glew.cmake     | 4 +++-
 src/external/levmar.cmake   | 4 +++-
 src/external/lib3ds.cmake   | 4 +++-
 src/external/libigl.cmake   | 4 +++-
 src/external/muparser.cmake | 4 +++-
 src/external/nexus.cmake    | 8 ++++++--
 src/external/openctm.cmake  | 4 +++-
 src/external/qhull.cmake    | 4 +++-
 src/external/ssynth.cmake   | 4 +++-
 src/external/tinygltf.cmake | 4 +++-
 src/external/u3d.cmake      | 4 +++-
 src/external/xerces.cmake   | 4 +++-
 15 files changed, 51 insertions(+), 17 deletions(-)

diff --git a/src/external/cgal.cmake b/src/external/cgal.cmake
index 3552a08ad..4317336c4 100644
--- a/src/external/cgal.cmake
+++ b/src/external/cgal.cmake
@@ -20,7 +20,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_CGAL)
 	set(CGAL_DOWNLOAD_SUCCESS TRUE)
 
 	if (NOT EXISTS ${CGAL_CHECK})
-		set(CGAL_LINK https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1.zip)
+		set(CGAL_LINK
+			https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1.zip
+			https://www.meshlab.net/data/libs/CGAL-5.2.1.zip)
 		set(CGAL_MD5 1a999ab90ea4cf28f6aa17ea2af24876)
 		download_and_unzip(
 			NAME "CGAL"
@@ -34,7 +36,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_CGAL)
 	endif()
 
 	if (WIN32 AND NOT EXISTS ${CGAL_WIN_CHECK})
-		set(CGAL_AUX_LINK https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1-win64-auxiliary-libraries-gmp-mpfr.zip)
+		set(CGAL_AUX_LINK
+			https://github.com/CGAL/cgal/releases/download/v5.2.1/CGAL-5.2.1-win64-auxiliary-libraries-gmp-mpfr.zip
+			https://www.meshlab.net/data/libs/CGAL-5.2.1-win64-auxiliary-libraries-gmp-mpfr.zip)
 		set(CGAL_AUX_MD5 247f4dca741c6b9a9be76286414070fa)
 		download_and_unzip(
 			NAME "CGAL auxiliary libraries"
diff --git a/src/external/e57.cmake b/src/external/e57.cmake
index 867b26a7b..6347caa08 100644
--- a/src/external/e57.cmake
+++ b/src/external/e57.cmake
@@ -10,7 +10,9 @@ if (TARGET XercesC::XercesC)
 		set(LIBE57_CHECK "${LIBE57_DIR}/CMakeLists.txt")
 
 		if (NOT EXISTS ${LIBE57_CHECK})
-			set(LIBE57_LINK https://github.com/asmaloney/libE57Format/archive/refs/tags/v2.3.0.zip)
+			set(LIBE57_LINK
+				https://github.com/asmaloney/libE57Format/archive/refs/tags/v2.3.0.zip
+				https://www.meshlab.net/data/libs/libE57Format-2.3.0.zip)
 			set(LIBE57_MD5 958ada3883f9b60195f79bbab156f3e3)
 			download_and_unzip(
 				NAME "LibE57"
diff --git a/src/external/easyexif.cmake b/src/external/easyexif.cmake
index d6f19b9ca..575a281d3 100644
--- a/src/external/easyexif.cmake
+++ b/src/external/easyexif.cmake
@@ -9,7 +9,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_EASYEXIF)
 	set(EASYEXIF_CHECK "${EASYEXIF_DIR}/exif.h")
 
 	if (NOT EXISTS ${EASYEXIF_CHECK})
-		set(EASYEXIF_LINK https://github.com/mayanklahiri/easyexif/archive/refs/tags/v1.0.zip)
+		set(EASYEXIF_LINK
+			https://github.com/mayanklahiri/easyexif/archive/refs/tags/v1.0.zip
+			https://www.meshlab.net/data/libs/easyexif-1.0.zip)
 		set(EASYEXIF_MD5 d46ec21b5c8ce13cda0fe66a4477a8c3)
 		download_and_unzip(
 			NAME "EasyExif"
diff --git a/src/external/glew.cmake b/src/external/glew.cmake
index fff07871f..0d16e915f 100644
--- a/src/external/glew.cmake
+++ b/src/external/glew.cmake
@@ -28,7 +28,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_GLEW)
 	set(GLEW_CHECK "${GLEW_DIR}/src/glew.c")
 
 	if (NOT EXISTS ${GLEW_CHECK})
-		set(GLEW_LINK https://github.com/nigels-com/glew/releases/download/glew-2.2.0/glew-2.2.0.zip)
+		set(GLEW_LINK
+			https://github.com/nigels-com/glew/releases/download/glew-2.2.0/glew-2.2.0.zip
+			https://www.meshlab.net/data/libs/glew-2.2.0.zip)
 		set(GLEW_MD5 970535b75b1b69ebd018a0fa05af63d1)
 		download_and_unzip(
 			NAME "GLEW"
diff --git a/src/external/levmar.cmake b/src/external/levmar.cmake
index fb5de25db..e5fe88c82 100644
--- a/src/external/levmar.cmake
+++ b/src/external/levmar.cmake
@@ -9,7 +9,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LEVMAR)
 	set(LEVMAR_CHECK "${LEVMAR_DIR}/lm.h")
 
 	if (NOT EXISTS ${LEVMAR_CHECK})
-		set(LEVMAR_LINK http://users.ics.forth.gr/~lourakis/levmar/levmar-2.6.tgz)
+		set(LEVMAR_LINK
+			http://users.ics.forth.gr/~lourakis/levmar/levmar-2.6.tgz
+			https://www.meshlab.net/data/libs/levmar-2.6.tgz)
 		set(LEVMAR_MD5 16bc34efa1617219f241eef06427f13f)
 		download_and_unzip(
 			NAME "Levmar"
diff --git a/src/external/lib3ds.cmake b/src/external/lib3ds.cmake
index 8d15dd076..0dde58b17 100644
--- a/src/external/lib3ds.cmake
+++ b/src/external/lib3ds.cmake
@@ -17,7 +17,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIB3DS)
 	set(LIB3DS_CHECK "${LIB3DS_DIR}/lib3ds/types.h")
 
 	if (NOT EXISTS ${LIB3DS_CHECK})
-		set(LIB3DS_LINK http://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/lib3ds/lib3ds-1.3.0.zip)
+		set(LIB3DS_LINK
+			http://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/lib3ds/lib3ds-1.3.0.zip
+			https://www.meshlab.net/data/libs/lib3ds-1.3.0.zip)
 		set(LIB3DS_MD5 2572f7b0f29b591d494c1a0658b35c86)
 		download_and_unzip(
 			NAME "Lib3DS"
diff --git a/src/external/libigl.cmake b/src/external/libigl.cmake
index 6554993c7..352cc34c9 100644
--- a/src/external/libigl.cmake
+++ b/src/external/libigl.cmake
@@ -9,7 +9,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_LIBIGL)
 	set(LIBIGL_CHECK "${LIBIGL_DIR}/include/igl/igl_inline.h")
 
 	if (NOT EXISTS ${LIBIGL_CHECK})
-		set(LIBIGL_LINK https://github.com/libigl/libigl/archive/refs/tags/v2.4.0.zip)
+		set(LIBIGL_LINK
+			https://github.com/libigl/libigl/archive/refs/tags/v2.4.0.zip
+			https://www.meshlab.net/data/libs/libigl-2.4.0.zip)
 		set(LIBIGL_MD5 0b4fea5dba2117b8db85c99a39a71f83)
 		download_and_unzip(
 			NAME "LibIGL"
diff --git a/src/external/muparser.cmake b/src/external/muparser.cmake
index ce33a7c0a..d14d25722 100644
--- a/src/external/muparser.cmake
+++ b/src/external/muparser.cmake
@@ -16,7 +16,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_MUPARSER)
 	set(MUPARSER_CHECK "${MUPARSER_DIR}/src/muParser.cpp")
 
 	if (NOT EXISTS ${MUPARSER_CHECK})
-		set(MUPARSER_LINK https://github.com/beltoforion/muparser/archive/refs/tags/v2.3.3-1.zip)
+		set(MUPARSER_LINK
+			https://github.com/beltoforion/muparser/archive/refs/tags/v2.3.3-1.zip
+			https://www.meshlab.net/data/libs/muparser-2.3.3-1.zip)
 		set(MUPARSER_MD5 8cf887ce460a405b8d8b966e0d5c94e3)
 		download_and_unzip(
 			NAME "muparser"
diff --git a/src/external/nexus.cmake b/src/external/nexus.cmake
index 9b22cdfdb..117634acc 100644
--- a/src/external/nexus.cmake
+++ b/src/external/nexus.cmake
@@ -12,7 +12,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS)
 	set(CORTO_CHECK "${CORTO_DIR}/CMakeLists.txt")
 
 	if (NOT EXISTS ${NEXUS_CHECK})
-		set(NEXUS_LINK https://github.com/cnr-isti-vclab/nexus/archive/refs/heads/master.zip)
+		set(NEXUS_LINK
+			https://github.com/cnr-isti-vclab/nexus/archive/refs/heads/master.zip
+			https://www.meshlab.net/data/libs/nexus-master.zip)
 		#set(NEXUS_MD5 3e50878dbaedd140f3e8c34d5af9a9d9)
 		download_and_unzip(
 			NAME "nexus"
@@ -26,7 +28,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_NEXUS)
 
 	if (NOT EXISTS ${CORTO_CHECK})
 		file(REMOVE_RECURSE ${NEXUS_DIR}/src/corto)
-		set(CORTO_LINK https://github.com/cnr-isti-vclab/corto/archive/refs/heads/master.zip)
+		set(CORTO_LINK
+			https://github.com/cnr-isti-vclab/corto/archive/refs/heads/master.zip
+			https://www.meshlab.net/data/libs/corto-master.zip)
 		#set(CORTO_MD5 ede1b41e369a8117d8f2f46fba89e11d)
 		download_and_unzip(
 			NAME "corto"
diff --git a/src/external/openctm.cmake b/src/external/openctm.cmake
index b293ef51c..c5dda5949 100644
--- a/src/external/openctm.cmake
+++ b/src/external/openctm.cmake
@@ -16,7 +16,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_OPENCTM)
 	set(OPENCTM_CHECK "${OPENCTM_DIR}/lib/openctm.c")
 
 	if (NOT EXISTS ${OPENCTM_CHECK})
-		set(OPENCTM_LINK https://sourceforge.net/projects/openctm/files/OpenCTM-1.0.3/OpenCTM-1.0.3-src.zip/download)
+		set(OPENCTM_LINK
+			https://sourceforge.net/projects/openctm/files/OpenCTM-1.0.3/OpenCTM-1.0.3-src.zip/download
+			https://www.meshlab.net/data/libs/OpenCTM-1.0.3-src.zip)
 		set(OPENCTM_MD5 a87b6a6509ae0712b4a55f8887dc6a54)
 		download_and_unzip(
 			NAME "OpenCTM"
diff --git a/src/external/qhull.cmake b/src/external/qhull.cmake
index 790116af4..c8a1174d9 100644
--- a/src/external/qhull.cmake
+++ b/src/external/qhull.cmake
@@ -16,7 +16,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_QHULL)
 	set(QHULL_CHECK "${QHULL_DIR}/src/libqhull_r/libqhull_r.h")
 
 	if (NOT EXISTS ${QHULL_CHECK})
-		set(QHULL_LINK https://github.com/qhull/qhull/archive/refs/tags/2020.2.zip)
+		set(QHULL_LINK
+			https://github.com/qhull/qhull/archive/refs/tags/2020.2.zip
+			https://www.meshlab.net/data/libs/qhull-2020.2.zip)
 		set(QHULL_MD5 a0a9b0e69bdbd9461319b8d2ac3d2f2e)
 		download_and_unzip(
 			NAME "Qhull"
diff --git a/src/external/ssynth.cmake b/src/external/ssynth.cmake
index bf6375310..5dea45a0b 100644
--- a/src/external/ssynth.cmake
+++ b/src/external/ssynth.cmake
@@ -9,7 +9,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_STRUCTURE_SYNTH)
 	set(SSYNTH_CHECK "${SSYNTH_DIR}/StructureSynth/Model/Action.h")
 
 	if (NOT EXISTS ${SSYNTH_CHECK})
-		set(SSYNTH_LINK https://github.com/alemuntoni/StructureSynth/archive/refs/tags/1.5.1.zip)
+		set(SSYNTH_LINK
+			https://github.com/alemuntoni/StructureSynth/archive/refs/tags/1.5.1.zip
+			https://www.meshlab.net/data/libs/StructureSynth-1.5.1.zip)
 		set(SSYNTH_MD5 e2122c5e6e370fb36c885bccf59562b7)
 		download_and_unzip(
 			NAME "Structure Synth"
diff --git a/src/external/tinygltf.cmake b/src/external/tinygltf.cmake
index 4a53f774c..768516f60 100644
--- a/src/external/tinygltf.cmake
+++ b/src/external/tinygltf.cmake
@@ -9,7 +9,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_TINYGLTF)
 	set(TINYGLTF_CHECK "${TINYGLTF_DIR}/tiny_gltf.h")
 
 	if (NOT EXISTS ${TINYGLTF_CHECK})
-		set(TINYGLTF_LINK https://github.com/syoyo/tinygltf/archive/refs/tags/v2.6.3.zip)
+		set(TINYGLTF_LINK
+			https://github.com/syoyo/tinygltf/archive/refs/tags/v2.6.3.zip
+			https://www.meshlab.net/data/libs/tinygltf-2.6.3.zip)
 		set(TINYGLTF_MD5 f63ab0fb59e5de059d9719cc14057dc8)
 		download_and_unzip(
 			NAME "tinygltf"
diff --git a/src/external/u3d.cmake b/src/external/u3d.cmake
index 80c8a8874..fb446a929 100644
--- a/src/external/u3d.cmake
+++ b/src/external/u3d.cmake
@@ -10,7 +10,9 @@ if(MESHLAB_ALLOW_DOWNLOAD_SOURCE_U3D)
 	set(U3D_CHECK "${U3D_DIR}/CMakeLists.txt")
 
 	if (NOT EXISTS ${U3D_CHECK})
-		set(U3D_LINK https://github.com/alemuntoni/u3d/archive/refs/heads/master.zip)
+		set(U3D_LINK
+			https://github.com/alemuntoni/u3d/archive/refs/heads/master.zip
+			https://www.meshlab.net/data/libs/u3d-master.zip)
 		#set(U3D_MD5 3b15b2f75206ea24b8991333562aa9ca)
 		download_and_unzip(
 			NAME "u3d"
diff --git a/src/external/xerces.cmake b/src/external/xerces.cmake
index fc94fd391..5a5e22208 100644
--- a/src/external/xerces.cmake
+++ b/src/external/xerces.cmake
@@ -17,7 +17,9 @@ elseif(MESHLAB_ALLOW_DOWNLOAD_SOURCE_XERCES)
 	set(XERCES_C_CHECK "${XERCES_C_DIR}/CMakeLists.txt")
 
 	if(NOT EXISTS ${XERCES_C_CHECK})
-		set(XERCES_C_LINK https://dlcdn.apache.org//xerces/c/3/sources/xerces-c-${XERCES_C_VER}.zip)
+		set(XERCES_C_LINK
+			https://dlcdn.apache.org//xerces/c/3/sources/xerces-c-${XERCES_C_VER}.zip
+			https://www.meshlab.net/data/libs/xerces-c-${XERCES_C_VER}.zip)
 		set(XERCES_C_MD5 f84488fc2b8f62c4afca2f9943a42c00)
 		download_and_unzip(
 			NAME "Xerces-C"