Pixyco-XYZ/openmesh
5
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Merge branch 'CalcFaceNormal' into 'master'

Browse Source 
implement more robust algorithm for surface normal computation

improved algorithm with Newell's Method

proposal to fix issue #7 ?

See merge request !14
This commit is contained in:
Jan Möbius
2015-11-04 15:03:37 +01:00
parent ea7d9ca510 2e709ae103
commit 0cd8fcb358
1 changed files with 17 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
src/OpenMesh/Core/Mesh/PolyMeshT.cc
View File

@@ -103,30 +103,31 @@ calc_face_normal(FaceHandle _fh) const
assert(this->halfedge_handle(_fh).is_valid()); assert(this->halfedge_handle(_fh).is_valid());
ConstFaceVertexIter fv_it(this->cfv_iter(_fh)); ConstFaceVertexIter fv_it(this->cfv_iter(_fh));
Point p0 = this->point(*fv_it);
const Point p0i = p0; //save point of vertex 0
// Safeguard for 1-gons // Safeguard for 1-gons
if (!(++fv_it).is_valid()) return Normal(0, 0, 0); if (!(++fv_it).is_valid()) return Normal(0, 0, 0);
Point p1 = this->point(*fv_it);
const Point p1i = p1; //save point of vertex 1
// Safeguard for 2-gons // Safeguard for 2-gons
if (!(++fv_it).is_valid()) return Normal(0, 0, 0); if (!(++fv_it).is_valid()) return Normal(0, 0, 0);
//calculate area-weighted average normal of polygon's ears // use Newell's Method to compute the surface normal
Normal n(0,0,0); Normal n(0,0,0);
for(; fv_it.is_valid(); ++fv_it) for(fv_it = this->cfv_iter(_fh); fv_it.is_valid(); ++fv_it)
{ {
const Point p2 = this->point(*fv_it); // next vertex
n += vector_cast<Normal>(calc_face_normal(p0, p1, p2)); ConstFaceVertexIter fv_itn = fv_it;
p0 = p1; ++fv_itn;
p1 = p2;
}
//two additional steps since we started at vertex 2, not 0 if (!fv_itn.is_valid())
n += vector_cast<Normal>(calc_face_normal(p0, p1, p0i)); fv_itn = this->cfv_iter(_fh);
n += vector_cast<Normal>(calc_face_normal(p1, p0i, p1i));
// http://www.opengl.org/wiki/Calculating_a_Surface_Normal
const Point a = this->point(*fv_it) - this->point(*fv_itn);
const Point b = this->point(*fv_it) + this->point(*fv_itn);
n[0] += a[1] * b[2];
n[1] += a[2] * b[0];
n[2] += a[0] * b[1];
}
const typename vector_traits<Normal>::value_type norm = n.length(); const typename vector_traits<Normal>::value_type norm = n.length();