Matrix44f LookAt(Vector3f eye, Vector3f center, Vector3f up) {
Matrix44f modelview;
Vector3f z = (eye - center).Normalize();
Vector3f x = CrossProduction(up, z).Normalize();
Vector3f y = CrossProduction(z, x).Normalize();
Matrix44f Minv = Matrix44f::Identity();
Matrix44f Tr = Matrix44f::Identity();
for (int i = 0; i < 3; i++) {
Minv[0][i] = x[i];
Minv[1][i] = y[i];
Minv[2][i] = z[i];
Tr[i][3] = -center[i];
}
modelview = Minv*Tr;
return modelview;
}
/**************************************************************************
MSHLib-Method:
Task:
Programing:
06/2005 WW Implementation
**************************************************************************/
void CElem::FillTransformMatrix()
{
if(transform_tensor)
return;
double xx[3];
double yy[3];
double zz[3];
transform_tensor = new Math_Group::Matrix(3,3);
if (geo_type == MshElemType::LINE)
{
// x"_vec
double const* const pnt0(nodes[0]->getData());
double const* const pnt1(nodes[1]->getData());
xx[0] = pnt1[0] - pnt0[0];
xx[1] = pnt1[1] - pnt0[1];
xx[2] = pnt1[2] - pnt0[2];
NormalizeVector(xx, 3);
// an arbitrary vector
for (size_t i = 0; i < 3; i++)
yy[i] = 0.0;
//WW. 06.11.2007
if (fabs(xx[0]) > 0.0 && fabs(xx[1]) + fabs(xx[2]) < DBL_MIN)
yy[2] = 1.0;
else if (fabs(xx[1]) > 0.0 && fabs(xx[0]) + fabs(xx[2]) < DBL_MIN)
yy[0] = 1.0;
else if (fabs(xx[2]) > 0.0 && fabs(xx[0]) + fabs(xx[1]) < DBL_MIN)
yy[1] = 1.0;
else
{
for (size_t i = 0; i < 3; i++)
if (fabs(xx[i]) > 0.0)
{
yy[i] = -xx[i];
break;
}
}
// z"_vec
CrossProduction(xx, yy, zz);
NormalizeVector(zz, 3);
// y"_vec
CrossProduction(zz, xx, yy);
NormalizeVector(yy, 3);
}
else if (geo_type == MshElemType::QUAD || geo_type == MshElemType::TRIANGLE)
{
// x"_vec
// xx[0] = nodes[1]->X() - nodes[0]->X();
// xx[1] = nodes[1]->Y() - nodes[0]->Y();
// xx[2] = nodes[1]->Z() - nodes[0]->Z();
double const* const pnt0(nodes[0]->getData());
double const* const pnt1(nodes[1]->getData());
xx[0] = pnt1[0] - pnt0[0];
xx[1] = pnt1[1] - pnt0[1];
xx[2] = pnt1[2] - pnt0[2];
NormalizeVector(xx, 3);
// a vector on the plane
// yy[0] = nodes[2]->X() - nodes[1]->X();
// yy[1] = nodes[2]->Y() - nodes[1]->Y();
// yy[2] = nodes[2]->Z() - nodes[1]->Z();
double const* const pnt2(nodes[2]->getData());
yy[0] = pnt2[0] - pnt1[0];
yy[1] = pnt2[1] - pnt1[1];
yy[2] = pnt2[2] - pnt1[2];
// z"_vec. off plane
CrossProduction(xx, yy, zz);
NormalizeVector(zz, 3);
// y"_vec
CrossProduction(zz, xx, yy);
NormalizeVector(yy, 3);
}
for (size_t i = 0; i < 3; i++)
{
(*transform_tensor)(i, 0) = xx[i];
(*transform_tensor)(i, 1) = yy[i];
(*transform_tensor)(i, 2) = zz[i];
}
}
