DGtal  1.5.beta
geometry/meshes/obj-curvature-measures-icnc-XY-3d.cpp

Computation of principal curvatures and directions on a mesh defined by an OBJ file, using interpolated corrected curvature measures (based on the theory of corrected normal currents).

# "spot" OBJ file
./examples/geometry/meshes/obj-curvature-measures-icnc-XY-3d ../examples/samples/spot.obj 0.05 15


outputs

[SurfaceMeshReader::readOBJ] Read #lines=12011 #V=2930 #VN=0 #F=5856
Mesh=[SurfaceMesh (OK) #V=2930 #VN=0 #E=8784 #F=5856 #FN=0 E[IF]=3 E[IV]=5.9959 E[IFE]=2] diameter=2.58809 radius=0.05
Computed k1 curvatures: min=-15.0745 max=14.493
Computed k2 curvatures: min=-0.0726101 max=18.3485


It also produces several OBJ files to display curvature estimation results, example-cnc-K1.obj, example-cnc-D1.obj, example-cnc-K2.obj, and example-cnc-D2.obj as well as the associated MTL file.

 Interpolated corrected smallest principal curvature and direction, r=0.05 Interpolated corrected greatest principal curvature and direction, r=0.05
Curvature measures on meshes and digital surfaces
#include <iostream>
#include <algorithm>
#include "DGtal/base/Common.h"
#include "DGtal/shapes/SurfaceMesh.h"
#include "DGtal/geometry/meshes/CorrectedNormalCurrentComputer.h"
#include "DGtal/io/writers/SurfaceMeshWriter.h"
#include "DGtal/helpers/Shortcuts.h"
#include "DGtal/io/colormaps/QuantifiedColorMap.h"
makeColorMap( double min_value, double max_value )
{
}
void usage( int argc, char* argv[] )
{
std::cout << "Usage: " << std::endl
<< "\t" << argv[ 0 ] << " <filename.obj> <R> <Kmax>" << std::endl
<< std::endl
<< "Computation of principal curvatures and directions on a mesh, " << std::endl
<< "using interpolated corrected curvature measures (based " << std::endl
<< "on the theory of corrected normal currents)." << std::endl
<< "- builds the surface mesh from file <filename.obj>" << std::endl
<< "- <R> is the radius of the measuring balls." << std::endl
<< "- <Kmax> gives the colormap range [-Kmax,Kmax] for" << std::endl
<< " the output of principal curvatures estimates" << std::endl
<< "It produces several OBJ files to display principal " << std::endl
<< "curvatures and directions estimations: example-cnc-K1.obj" << std::endl
<< "example-cnc-K2.obj, example-cnc-D1.obj, and" << std::endl
<< "example-cnc-D2.obj as well as associated MTL files." << std::endl;
}
int main( int argc, char* argv[] )
{
if ( argc <= 1 )
{
usage( argc, argv );
return 0;
}
using namespace DGtal;
using namespace DGtal::Z3i;
typedef SurfaceMesh< RealPoint, RealVector > SM;
typedef CorrectedNormalCurrentComputer< RealPoint, RealVector > CNC;
typedef SurfaceMeshReader< RealPoint, RealVector > SMR;
// OBJ file
std::string input = argv[ 1 ];
const double R = argc > 2 ? atof( argv[ 2 ] ) : 0.0; // radius of measuring ball
const double Kmax = argc > 3 ? atof( argv[ 3 ] ) : 5.0; // range curvature colormap
SM smesh;
std::ifstream obj_stream( input.c_str() );
bool ok = SMR::readOBJ( obj_stream, smesh );
if ( !ok )
{
trace.error() << "Unable to read file <" << input.c_str() << ">" << std::endl;
return 1;
}
RealPoint lo = smesh.position( 0 );
RealPoint up = smesh.position( 0 );
for ( const auto& p : smesh.positions() )
lo = lo.inf( p ), up = up.sup( p );
const auto diameter = (up - lo).norm();
trace.info() << "Mesh=" << smesh
<< " diameter=" << diameter
<< " radius=" << R << std::endl;
// builds a CorrectedNormalCurrentComputer object onto the mesh
CNC cnc( smesh );
// computes normals if necessary
if ( smesh.vertexNormals().empty() )
{
if ( smesh.faceNormals().empty() )
smesh.computeFaceNormalsFromPositions();
smesh.computeVertexNormalsFromFaceNormals();
}
// computes area, anisotropic XY curvature measures
auto mu0 = cnc.computeMu0();
auto muXY = cnc.computeMuXY();
// estimates mean (H) and Gaussian (G) curvatures by measure normalization.
std::vector< double > K1( smesh.nbFaces() );
std::vector< double > K2( smesh.nbFaces() );
std::vector< RealVector > D1( smesh.nbFaces() );
std::vector< RealVector > D2( smesh.nbFaces() );
smesh.computeFaceNormalsFromPositions();
for ( auto f = 0; f < smesh.nbFaces(); ++f )
{
const auto b = smesh.faceCentroid( f );
const auto N = smesh.faceNormals()[ f ];
const auto area = mu0 .measure( b, R, f );
const auto M = muXY.measure( b, R, f );
std::tie( K1[ f ], K2[ f ], D1[ f ], D2[ f ] )
= cnc.principalCurvatures( area, M, N );
}
auto K1_min_max = std::minmax_element( K1.cbegin(), K1.cend() );
auto K2_min_max = std::minmax_element( K2.cbegin(), K2.cend() );
std::cout << "Computed k1 curvatures:"
<< " min=" << *K1_min_max.first << " max=" << *K1_min_max.second
<< std::endl;
std::cout << "Computed k2 curvatures:"
<< " min=" << *K2_min_max.first << " max=" << *K2_min_max.second
<< std::endl;
typedef SurfaceMeshWriter< RealPoint, RealVector > SMW;
typedef Shortcuts< KSpace > SH;
const auto colormapK1 = makeQuantifiedColorMap( makeColorMap( -Kmax, Kmax ) );
const auto colormapK2 = makeQuantifiedColorMap( makeColorMap( -Kmax, Kmax ) );
auto colorsK1 = SMW::Colors( smesh.nbFaces() );
auto colorsK2 = SMW::Colors( smesh.nbFaces() );
for ( auto i = 0; i < smesh.nbFaces(); i++ )
{
colorsK1[ i ] = colormapK1( K1[ i ] );
colorsK2[ i ] = colormapK2( K2[ i ] );
}
SMW::writeOBJ( "example-cnc-K1", smesh, colorsK1 );
SMW::writeOBJ( "example-cnc-K2", smesh, colorsK2 );
const auto avg_e = smesh.averageEdgeLength();
SH::RealPoints positions( smesh.nbFaces() );
for ( auto f = 0; f < positions.size(); ++f )
{
D1[ f ] *= smesh.localWindow( f );
positions[ f ] = smesh.faceCentroid( f ) - 0.5 * D1[ f ];
}
SH::saveVectorFieldOBJ( positions, D1, 0.05 * avg_e, SH::Colors(),
"example-cnc-D1",
SH::Color::Black, SH::Color( 0, 128, 0 ) );
for ( auto f = 0; f < positions.size(); ++f )
{
D2[ f ] *= smesh.localWindow( f );
positions[ f ] = smesh.faceCentroid( f ) - 0.5 * D2[ f ];
}
SH::saveVectorFieldOBJ( positions, D2, 0.05 * avg_e, SH::Colors(),
"example-cnc-D2",
SH::Color::Black, SH::Color(128, 0,128 ) );
return 0;
}
void usage(int, char **argv)
Structure representing an RGB triple with alpha component.
Definition: Color.h:68
Aim: This class template may be used to (linearly) convert scalar values in a given range into a colo...