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Improved EarClipTesselator.

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More resillient against zero area ears.
Less prone to make invalid traingles due to vertices touching edge
but might fail to produce triangles at all in that case.
This commit is contained in:
Jacob Støren 2020-01-24 11:14:37 +01:00
parent 1949940b96
commit cb664d9820
2 changed files with 38 additions and 16 deletions
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41
ApplicationCode/ReservoirDataModel/cvfGeometryTools.cpp
View File

@ -880,12 +880,17 @@ bool EarClipTesselator::calculateTriangles( std::vector<size_t>* triangleIndices
++w; // v + 1;
if ( w == m_polygonIndices.end() ) w = m_polygonIndices.begin(); // if (nv <= w) w = 0;
if ( isTriangleValid( u, v, w ) )
EarClipTesselator::TriangleStatus triStatus = calculateTriangleStatus( u, v, w );
if ( triStatus != INVALID_TRIANGLE )
{
// Indices of the vertices
triangleIndices->push_back( *u );
triangleIndices->push_back( *v );
triangleIndices->push_back( *w );
if ( triStatus == VALID_TRIANGLE )
{
triangleIndices->push_back( *u );
triangleIndices->push_back( *v );
triangleIndices->push_back( *w );
}
// Remove v from remaining polygon
m_polygonIndices.erase( v );
@ -904,9 +909,9 @@ bool EarClipTesselator::calculateTriangles( std::vector<size_t>* triangleIndices
/// Is this a valid triangle ? ( No points inside, and points not on a line. )
//--------------------------------------------------------------------------------------------------
bool EarClipTesselator::isTriangleValid( std::list<size_t>::const_iterator u,
std::list<size_t>::const_iterator v,
std::list<size_t>::const_iterator w ) const
EarClipTesselator::TriangleStatus EarClipTesselator::calculateTriangleStatus( std::list<size_t>::const_iterator u,
std::list<size_t>::const_iterator v,
std::list<size_t>::const_iterator w ) const
{
CVF_ASSERT( m_X > -1 && m_Y > -1 );
@ -914,9 +919,17 @@ bool EarClipTesselator::isTriangleValid( std::list<size_t>::const_iterator u,
cvf::Vec3d B = ( *m_nodeCoords )[*v];
cvf::Vec3d C = ( *m_nodeCoords )[*w];
if ( m_areaTolerance >
( ( ( B[m_X] - A[m_X] ) * ( C[m_Y] - A[m_Y] ) ) - ( ( B[m_Y] - A[m_Y] ) * ( C[m_X] - A[m_X] ) ) ) )
return false;
double mainAxisProjectedArea = ( ( B[m_X] - A[m_X] ) * ( C[m_Y] - A[m_Y] ) ) -
( ( B[m_Y] - A[m_Y] ) * ( C[m_X] - A[m_X] ) );
if ( -m_areaTolerance > mainAxisProjectedArea )
{
// Definite negative triangle
return INVALID_TRIANGLE;
}
else if ( fabs( mainAxisProjectedArea ) < m_areaTolerance )
{
return NEAR_ZERO_AREA_TRIANGLE;
}
std::list<size_t>::const_iterator c;
std::list<size_t>::const_iterator outside;
@ -948,15 +961,16 @@ bool EarClipTesselator::isTriangleValid( std::list<size_t>::const_iterator u,
cvf::Vec3d P = ( *m_nodeCoords )[*c];
if ( isPointInsideTriangle( A, B, C, P ) ) return false;
if ( isPointInsideTriangle( A, B, C, P ) ) return INVALID_TRIANGLE;
}
return true;
return VALID_TRIANGLE;
}
//--------------------------------------------------------------------------------------------------
/// Decides if a point P is inside of the triangle defined by A, B, C.
/// By calculating the "double area" (cross product) of Corner to corner x Corner to point vectors
/// If cross product is negative, the point is outside
//--------------------------------------------------------------------------------------------------
bool EarClipTesselator::isPointInsideTriangle( const cvf::Vec3d& A,
@ -983,7 +997,8 @@ bool EarClipTesselator::isPointInsideTriangle( const cvf::Vec3d& A,
double aCROSSbp = ax * bpy - ay * bpx;
double cCROSSap = cx * apy - cy * apx;
double bCROSScp = bx * cpy - by * cpx;
double tol = 0;
double tol = -m_areaTolerance;
return ( ( aCROSSbp >= tol ) && ( bCROSScp >= tol ) && ( cCROSSap >= tol ) );
};

13
ApplicationCode/ReservoirDataModel/cvfGeometryTools.h
View File

@ -209,9 +209,16 @@ public:
virtual bool calculateTriangles( std::vector<size_t>* triangles );
protected:
bool isTriangleValid( std::list<size_t>::const_iterator u,
std::list<size_t>::const_iterator v,
std::list<size_t>::const_iterator w ) const;
enum TriangleStatus
{
INVALID_TRIANGLE,
NEAR_ZERO_AREA_TRIANGLE,
VALID_TRIANGLE
};
TriangleStatus calculateTriangleStatus( std::list<size_t>::const_iterator u,
std::list<size_t>::const_iterator v,
std::list<size_t>::const_iterator w ) const;
bool isPointInsideTriangle( const cvf::Vec3d& A, const cvf::Vec3d& B, const cvf::Vec3d& C, const cvf::Vec3d& P ) const;
double calculateProjectedPolygonArea() const;