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Restructured a bit the stratified sampling approaches

This commit is contained in:
Paolo Cignoni 2009-03-19 22:04:52 +00:00
parent 93dade9042
commit 2ba11ecc4a
1 changed files with 68 additions and 20 deletions
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84
vcg/complex/trimesh/point_sampling.h
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@ -536,47 +536,94 @@ static int SingleFaceSimilar(FacePointer fp, VertexSampler &ps, int n_samples_pe
} }
return n_samples; return n_samples;
} }
static int SingleFaceSimilarDual(FacePointer fp, VertexSampler &ps, int n_samples_per_edge, bool randomFlag)
{
int n_samples=0;
float i, j;
float segmentNum=n_samples_per_edge -1 ;
float segmentLen = 1.0/segmentNum;
// face sampling.
for(i=0; i < n_samples_per_edge-1; i++)
for(j=0; j < n_samples_per_edge-1-i; j++)
{
//AddSample( v0 + (V1*(double)i + V2*(double)j) );
CoordType V0((i+0)*segmentLen,(j+0)*segmentLen, 1.0 - ((i+0)*segmentLen+(j+0)*segmentLen) ) ;
CoordType V1((i+1)*segmentLen,(j+0)*segmentLen, 1.0 - ((i+1)*segmentLen+(j+0)*segmentLen) ) ;
CoordType V2((i+0)*segmentLen,(j+1)*segmentLen, 1.0 - ((i+0)*segmentLen+(j+1)*segmentLen) ) ;
n_samples++;
if(randomFlag) {
CoordType rb=RandomBaricentric();
ps.AddFace(*fp, V0*rb[0]+V1*rb[1]+V2*rb[2]);
} else ps.AddFace(*fp,(V0+V1+V2)/3.0);
/// Similar sampling. Each triangle is subdivided into similar triangles following a generalization of the classical 1-to-4 splitting rule of triangles. if( j < n_samples_per_edge-i-2 )
/// According to the level of subdivision <k> you get 1, 4 , 9, 16 , <k^2> triangles. {
/// Of these triangles we consider only internal vertices. (to avoid multiple sampling of edges and vertices). CoordType V3((i+1)*segmentLen,(j+1)*segmentLen, 1.0 - ((i+1)*segmentLen+(j+1)*segmentLen) ) ;
/// Therefore the number of internal points is ((k-3)*(k-2))/2. where k is the number of point on an edge (vertex included) n_samples++;
// e.g. for a k=4 you get (1*2)/2 == 1 e.g. a single point, etc. if(randomFlag) {
/// So if you want N samples in a triangle i have to solve k^2 -5k +6 - 2N = 0 CoordType rb=RandomBaricentric();
ps.AddFace(*fp, V3*rb[0]+V1*rb[1]+V2*rb[2]);
} else ps.AddFace(*fp,(V3+V1+V2)/3.0);
}
}
return n_samples;
}
// Similar sampling
// Each triangle is subdivided into similar triangles following a generalization of the classical 1-to-4 splitting rule of triangles.
// According to the level of subdivision <k> you get 1, 4 , 9, 16 , <k^2> triangles.
// Depending on the kind of the sampling strategies we can have two different approach to choosing the sample points.
// 1) you have already sampled both edges and vertices
// 2) you are not going to take samples on edges and vertices.
//
// In the first case you have to consider only internal vertices of the subdivided triangles (to avoid multiple sampling of edges and vertices).
// Therefore the number of internal points is ((k-3)*(k-2))/2. where k is the number of points on an edge (vertex included)
// E.g. for k=4 you get 3 segments on each edges and the original triangle is subdivided
// into 9 smaller triangles and you get (1*2)/2 == 1 only a single internal point.
// So if you want N samples in a triangle you have to solve k^2 -5k +6 - 2N = 0
// from which you get:
//
// 5 + sqrt( 1 + 8N ) // 5 + sqrt( 1 + 8N )
// k = ------------------- // k = -------------------
// 2 // 2
//
// In the second case if you are not interested to skip the sampling on edges and vertices you have to consider as sample number the number of triangles.
// So if you want N samples in a triangle, the number <k> of points on an edge (vertex included) should be simply:
// k = 1 + sqrt(N)
// examples:
// N = 4 -> k = 3
// N = 9 -> k = 4
//template <class MetroMesh> //template <class MetroMesh>
//void Sampling<MetroMesh>::SimilarFaceSampling() //void Sampling<MetroMesh>::SimilarFaceSampling()
static void FaceSimilar(MetroMesh & m, VertexSampler &ps,int sampleNum) static void FaceSimilar(MetroMesh & m, VertexSampler &ps,int sampleNum, bool dualFlag, bool randomFlag)
{ {
ScalarType area = Stat<MetroMesh>::ComputeMeshArea(m); ScalarType area = Stat<MetroMesh>::ComputeMeshArea(m);
ScalarType samplePerAreaUnit = sampleNum/area; ScalarType samplePerAreaUnit = sampleNum/area;
//qDebug("samplePerAreaUnit %f",samplePerAreaUnit);
// Similar Triangles sampling. // Similar Triangles sampling.
int n_samples_per_edge; int n_samples_per_edge;
double n_samples_decimal = 0.0; double n_samples_decimal = 0.0;
FaceIterator fi; FaceIterator fi;
printf("Similar Triangles face sampling\n");
for(fi=m.face.begin(); fi != m.face.end(); fi++) for(fi=m.face.begin(); fi != m.face.end(); fi++)
{ {
// compute # samples in the current face. // compute # samples in the current face.
n_samples_decimal += 0.5*DoubleArea(*fi) * samplePerAreaUnit; n_samples_decimal += 0.5*DoubleArea(*fi) * samplePerAreaUnit;
int n_samples = (int) n_samples_decimal; int n_samples = (int) n_samples_decimal;
if(n_samples) if(n_samples>0)
{ {
// face sampling. // face sampling.
n_samples_per_edge = (int)((sqrt(1.0+8.0*(double)n_samples) +5.0)/2.0); if(dualFlag)
//n_samples = 0; {
//SingleFaceSimilar((*fi).V(0)->cP(), (*fi).V(1)->cP(), (*fi).V(2)->cP(), n_samples_per_edge); n_samples_per_edge = (int)((sqrt(1.0+8.0*(double)n_samples) +5.0)/2.0); // original for non dual case
n_samples = SingleFaceSimilar(&*fi,ps, n_samples_per_edge); n_samples = SingleFaceSimilar(&*fi,ps, n_samples_per_edge);
} else {
n_samples_per_edge = (int)(sqrt(n_samples) +1.0);
n_samples = SingleFaceSimilarDual(&*fi,ps, n_samples_per_edge,randomFlag);
}
} }
n_samples_decimal -= (double) n_samples; n_samples_decimal -= (double) n_samples;
} }
@ -787,7 +834,7 @@ static void Poissondisk(MetroMesh &origMesh, VertexSampler &ps, MetroMesh &monte
int sizeY = vcg::math::Max(1.0f,origMesh.bbox.DimY() / cellsize); int sizeY = vcg::math::Max(1.0f,origMesh.bbox.DimY() / cellsize);
int sizeZ = vcg::math::Max(1.0f,origMesh.bbox.DimZ() / cellsize); int sizeZ = vcg::math::Max(1.0f,origMesh.bbox.DimZ() / cellsize);
Point3i gridsize(sizeX, sizeY, sizeZ); Point3i gridsize(sizeX, sizeY, sizeZ);
#ifndef NO_QT #ifdef QT_VERSION
qDebug("PDS: radius %f Grid:(%i %i %i) ",diskRadius,sizeX,sizeY,sizeZ); qDebug("PDS: radius %f Grid:(%i %i %i) ",diskRadius,sizeX,sizeY,sizeZ);
#endif #endif
// initialize spatial hash to index pre-generated samples // initialize spatial hash to index pre-generated samples
@ -798,7 +845,7 @@ static void Poissondisk(MetroMesh &origMesh, VertexSampler &ps, MetroMesh &monte
montecarloSHT.Add(&(*vi)); montecarloSHT.Add(&(*vi));
verticescounter[0]++; verticescounter[0]++;
} }
#ifndef NO_QT #ifdef QT_VERSION
qDebug("PDS: Completed montercarloSHT, inserted %i vertex in %i cells", montecarloMesh.vn, montecarloSHT.AllocatedCells.size()); qDebug("PDS: Completed montercarloSHT, inserted %i vertex in %i cells", montecarloMesh.vn, montecarloSHT.AllocatedCells.size());
#endif #endif
// initialize spatial hash table for check poisson-disk radius constrain // initialize spatial hash table for check poisson-disk radius constrain
@ -927,14 +974,14 @@ static void Poissondisk(MetroMesh &origMesh, VertexSampler &ps, MetroMesh &monte
} }
nextPoints.clear(); nextPoints.clear();
#ifndef NO_QT #ifdef QT_VERSION
qDebug("PDS: Completed Level %i, added %i samples",level,samplesaccepted[level]); qDebug("PDS: Completed Level %i, added %i samples",level,samplesaccepted[level]);
#endif #endif
level++; level++;
} while(level < pp.MAXLEVELS); } while(level < pp.MAXLEVELS);
#ifndef NO_QT #ifdef DEBUG_DUMP_STAT
// write some statistics // write some statistics
QFile outfile("C:/temp/poissondisk_statistics.txt"); QFile outfile("C:/temp/poissondisk_statistics.txt");
if (outfile.open(QFile::WriteOnly | QFile::Truncate)) if (outfile.open(QFile::WriteOnly | QFile::Truncate))
@ -987,3 +1034,4 @@ static void Texture(MetroMesh & m, VertexSampler &ps, int textureWidth, int text
} // end namespace vcg } // end namespace vcg
#endif #endif