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loss of precision management

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This commit is contained in:
Paolo Cignoni cignoni 2008-03-02 15:15:50 +00:00
parent ddcabf81ac
commit c143069fd1
1 changed files with 87 additions and 43 deletions
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130
src/meshlabplugins/meshfilter/quadric5.h
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@ -23,6 +23,9 @@
/****************************************************************************
History
$Log$
Revision 1.4 2008/03/02 15:15:50 pirosu
loss of precision management
Revision 1.3 2008/02/29 20:37:27 pirosu
fixed zero area faces management
@ -91,6 +94,17 @@ public:
c = 0;
}
void swapv(ScalarType *vv, ScalarType *ww)
{
ScalarType tmp;
for(int i = 0; i < 5; i++)
{
tmp = vv[i];
vv[i] = ww[i];
ww[i] = tmp;
}
}
// computes the real quadric and the geometric quadric using the face
// The geometric quadric is added to the parameter qgeo
void byFace(FaceType &f, math::Quadric<double> &q1, math::Quadric<double> &q2, math::Quadric<double> &q3)
@ -235,58 +249,88 @@ public:
r[4] = 0;
}
// computes e1
sub_vec5(q,p,e1);
normalize_vec5(e1);
// computes e2
sub_vec5(r,p,diffe);
outproduct5(e1,diffe,tmpmat);
prod_matvec5(tmpmat,e1,tmpvec);
sub_vec5(diffe,tmpvec,e2);
normalize_vec5(e2);
/*
When c is very close to 0, loss of precision causes it to be computed as a negative number,
which is invalid for a quadric. Vertex switches are performed in order to try to obtain a smaller
loss of precision
*/
for(int i = 0; i < 6; i++) // tries the 6! configurations
{
switch(i)
{
case 0:
break;
case 1:
case 3:
case 5:
swapv(q,r);
break;
case 2:
case 4:
swapv(p,r);
break;
default:
assert(0);
}
// computes e1
sub_vec5(q,p,e1);
normalize_vec5(e1);
// computes e2
sub_vec5(r,p,diffe);
outproduct5(e1,diffe,tmpmat);
prod_matvec5(tmpmat,e1,tmpvec);
sub_vec5(diffe,tmpvec,e2);
normalize_vec5(e2);
// computes A
a[0] = 1;
a[1] = 0;
a[2] = 0;
a[3] = 0;
a[4] = 0;
a[5] = 1;
a[6] = 0;
a[7] = 0;
a[8] = 0;
a[9] = 1;
a[10] = 0;
a[11] = 0;
a[12] = 1;
a[13] = 0;
a[14] = 1;
// computes A
a[0] = 1;
a[1] = 0;
a[2] = 0;
a[3] = 0;
a[4] = 0;
a[5] = 1;
a[6] = 0;
a[7] = 0;
a[8] = 0;
a[9] = 1;
a[10] = 0;
a[11] = 0;
a[12] = 1;
a[13] = 0;
a[14] = 1;
symprod_vvt5(tmpsymmat,e1);
sub_symmat5(a,tmpsymmat);
symprod_vvt5(tmpsymmat,e2);
sub_symmat5(a,tmpsymmat);
symprod_vvt5(tmpsymmat,e1);
sub_symmat5(a,tmpsymmat);
symprod_vvt5(tmpsymmat,e2);
sub_symmat5(a,tmpsymmat);
pe1 = inproduct5(p,e1);
pe2 = inproduct5(p,e2);
// computes b
pe1 = inproduct5(p,e1);
pe2 = inproduct5(p,e2);
// computes b
tmpvec[0] = pe1*e1[0] + pe2*e2[0];
tmpvec[1] = pe1*e1[1] + pe2*e2[1];
tmpvec[2] = pe1*e1[2] + pe2*e2[2];
tmpvec[3] = pe1*e1[3] + pe2*e2[3];
tmpvec[4] = pe1*e1[4] + pe2*e2[4];
tmpvec[0] = pe1*e1[0] + pe2*e2[0];
tmpvec[1] = pe1*e1[1] + pe2*e2[1];
tmpvec[2] = pe1*e1[2] + pe2*e2[2];
tmpvec[3] = pe1*e1[3] + pe2*e2[3];
tmpvec[4] = pe1*e1[4] + pe2*e2[4];
sub_vec5(tmpvec,p,b);
sub_vec5(tmpvec,p,b);
// computes c
c = inproduct5(p,p)-pe1*pe1-pe2*pe2;
// computes c
c = inproduct5(p,p)-pe1*pe1-pe2*pe2;
assert(IsValid());
if(IsValid())return;
}
// failed to find a valid vertex switch
assert(-c <= 1e-8); // small error
c = 0; // rounds up to zero
}
bool Gauss55( ScalarType x[], ScalarType C[5][5+1] )