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68 lines
1.7 KiB
GLSL
68 lines
1.7 KiB
GLSL
//
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// Fragment shader for environment mapping with an
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// equirectangular 2D texture
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//
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// Authors: John Kessenich, Randi Rost
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//
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// Copyright (c) 2002-2004 3Dlabs Inc. Ltd.
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//
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// See 3Dlabs-License.txt for license information
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//
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const vec3 Xunitvec = vec3 (1.0, 0.0, 0.0);
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const vec3 Yunitvec = vec3 (0.0, 1.0, 0.0);
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uniform vec3 BaseColor;
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uniform float MixRatio;
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uniform sampler2D EnvMap;
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varying vec3 Normal;
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varying vec3 EyeDir;
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//varying float LightIntensity;
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void main (void)
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{
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// Compute reflection vector
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vec3 reflectDir = reflect(EyeDir, Normal);
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//---- this is the original code (buggy):
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// // Compute altitude and azimuth angles
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//
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// index.y = dot(normalize(reflectDir), Yunitvec);
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// reflectDir.y = 0.0;
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// index.x = dot(normalize(reflectDir), Xunitvec) * 0.5;
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//
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// // Translate index values into proper range
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//
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// if (reflectDir.z >= 0.0)
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// index = (index + 1.0) * 0.5;
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// else
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// {
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// index.t = (index.t + 1.0) * 0.5;
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// index.s = (-index.s) * 0.5 + 1.0;
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// }
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//
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// // if reflectDir.z >= 0.0, s will go from 0.25 to 0.75
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// // if reflectDir.z < 0.0, s will go from 0.75 to 1.25, and
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// // that's OK, because we've set the texture to wrap.
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//---- end of the original code
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// this is the version implemented from the OpenGL-1.2 programming guide:
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reflectDir.z += 1.0;
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float inv_m = 0.5/sqrt(dot(reflectDir,reflectDir));
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vec2 index = reflectDir.xy * inv_m + 0.5;
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// Do a lookup into the environment map.
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vec4 envColor = vec4 (texture2D(EnvMap, index));
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// Add lighting to base color and mix
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//vec3 base = LightIntensity * BaseColor;
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envColor = mix(envColor, gl_Color, MixRatio);
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gl_FragColor =envColor;
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}
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