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Added a function Flip a mesh so that its normals are orented outside. 

Just for safety it uses a voting scheme.
It assumes that
* mesh has already has coherent normals.
* mesh is watertight and single component.
This commit is contained in:
Paolo Cignoni 2011-04-07 22:28:28 +00:00
parent d967184dee
commit 5233b20f12
1 changed files with 54 additions and 0 deletions
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54
vcg/complex/algorithms/clean.h
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@ -1150,6 +1150,60 @@ private:
std::swap((*fi).WT(0),(*fi).WT(1)); std::swap((*fi).WT(0),(*fi).WT(1));
} }
} }
/// Flip a mesh so that its normals are orented outside.
/// Just for safety it uses a voting scheme.
/// It assumes that
/// mesh has already has coherent normals.
/// mesh is watertight and signle component.
static bool FlipNormalOutside(MeshType &m)
{
if(m.vert.empty()) return false;
tri::UpdateNormals<MeshType>::PerVertexAngleWeighted(m);
tri::UpdateNormals<MeshType>::NormalizeVertex(m);
std::vector< VertexPointer > minVertVec;
std::vector< VertexPointer > maxVertVec;
// The set of directions to be choosen
std::vector< Point3x > dirVec;
dirVec.push_back(Point3x(1,0,0));
dirVec.push_back(Point3x(0,1,0));
dirVec.push_back(Point3x(0,0,1));
dirVec.push_back(Point3x( 1, 1,1));
dirVec.push_back(Point3x(-1, 1,1));
dirVec.push_back(Point3x(-1,-1,1));
dirVec.push_back(Point3x( 1,-1,1));
for(size_t i=0;i<dirVec.size();++i)
{
Normalize(dirVec[i]);
minVertVec.push_back(&*m.vert.begin());
maxVertVec.push_back(&*m.vert.begin());
}
for (VertexIterator vi = m.vert.begin(); vi != m.vert.end(); ++vi) if(!(*vi).IsD())
{
for(size_t i=0;i<dirVec.size();++i)
{
if( (*vi).cP().dot(dirVec[i]) < minVertVec[i]->P().dot(dirVec[i])) minVertVec[i] = &*vi;
if( (*vi).cP().dot(dirVec[i]) > maxVertVec[i]->P().dot(dirVec[i])) maxVertVec[i] = &*vi;
}
}
int voteCount=0;
ScalarType angleThreshold = cos(math::ToRad(85.0));
for(size_t i=0;i<dirVec.size();++i)
{
// qDebug("Min vert along (%f %f %f) is %f %f %f",dirVec[i][0],dirVec[i][1],dirVec[i][2],minVertVec[i]->P()[0],minVertVec[i]->P()[1],minVertVec[i]->P()[2]);
// qDebug("Max vert along (%f %f %f) is %f %f %f",dirVec[i][0],dirVec[i][1],dirVec[i][2],maxVertVec[i]->P()[0],maxVertVec[i]->P()[1],maxVertVec[i]->P()[2]);
if(minVertVec[i]->N().dot(dirVec[i]) > angleThreshold ) voteCount++;
if(maxVertVec[i]->N().dot(dirVec[i]) < -angleThreshold ) voteCount++;
}
// qDebug("votecount = %i",voteCount);
if(voteCount < dirVec.size()/2) return false;
FlipMesh(m);
return true;
}
// Search and remove small single triangle folds // Search and remove small single triangle folds
// - a face has normal opposite to all other faces // - a face has normal opposite to all other faces
// - choose the edge that brings to the face f1 containing the vertex opposite to that edge. // - choose the edge that brings to the face f1 containing the vertex opposite to that edge.