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Fix Degenerate geometry (generating very stretched triangles) #507

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Fix Degenerate geometry (generating very stretched triangles) #507

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17893f9
fix degenerated faces
Nov 19, 2024
9d54c80
change tests
Nov 19, 2024
4a11262
remove my tests
r-silveira Nov 19, 2024
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24 changes: 22 additions & 2 deletions Xbim.Geometry.Engine/XbimOccShape.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -356,6 +356,9 @@ namespace Xbim
List<List<int>^>^ tessellations = gcnew List<List<int>^>(faceCount);
bool isPolyhedron = true;
array<bool>^ hasSeams = gcnew array<bool>(faceCount);

bool foundDegenerate = false;

//we check if the shape is a faceted poltgon, i.e. all faces are planar and all edges are linear, if so then we do not need to use OCC meshing which is general purpose and a little slower than LibMesh
for (int f = 1; f <= faceMap.Extent(); f++)
{
Expand Down Expand Up @@ -524,15 +527,25 @@ namespace Xbim
{
array<ContourVertex>^ outerContour = gcnew array<ContourVertex>(numberEdges);
BRepTools_WireExplorer exp(outerWire, face);
for (int j = 0; exp.More(); exp.Next())

int j = 0;
for (j = 0; exp.More(); exp.Next())
{
gp_Pnt p = BRep_Tool::Pnt(exp.CurrentVertex());
outerContour[j].Position.X = p.X();
outerContour[j].Position.Y = p.Y();
outerContour[j].Position.Z = p.Z();
j++;
}
tess->AddContour(outerContour); //the original winding is correct as we have oriented the wire to the face in BRepTools_WireExplorer

if (j == numberEdges)
{
tess->AddContour(outerContour); //the original winding is correct as we have oriented the wire to the face in BRepTools_WireExplorer
}
else
{
foundDegenerate = true;
}
}

}
Expand All @@ -559,6 +572,13 @@ namespace Xbim
}
}
}

if (foundDegenerate)
{
foundDegenerate = false;
continue;
}

tess->Tessellate(Xbim::Tessellator::WindingRule::EvenOdd, Xbim::Tessellator::ElementType::Polygons, 3);
if (tess->ElementCount > 0) //we have some triangles
{
Expand Down