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Fix surface orientation in quest::STEPReader #1765

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Merged
jcs15c merged 5 commits into from
Jan 13, 2026
Merged

Fix surface orientation in quest::STEPReader #1765

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bb45a57
Update with orientation fix
jcs15c Jan 9, 2026
3535194
merge develop
jcs15c Jan 9, 2026
9cd9541
merge again, fix a broken guard in MeshClipper
jcs15c Jan 9, 2026
7d1f756
Add the extra flag for trimmed surfaces
jcs15c Jan 9, 2026
f349ca4
Merge branch 'develop' into bugfix/spainhour/stepreader_orientation
jcs15c Jan 13, 2026
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2 changes: 1 addition & 1 deletion src/axom/quest/MeshClipper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -237,8 +237,8 @@ void globalReduce(axom::Array<T>& values, int reduceOp)
axom::mpi_traits<T>::type,
reduceOp,
MPI_COMM_WORLD);
#endif
}
#endif

void MeshClipper::accumulateClippingStats(conduit::Node& curStats, const conduit::Node& newStats)
{
Expand Down
48 changes: 27 additions & 21 deletions src/axom/quest/io/STEPReader.cpp
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Expand Up @@ -123,7 +123,7 @@ class StepFileProcessor
return bbox;
}

/// Helper class to convert faces of CAD mesh to valid NURBSPatch instances
/// Helper class to convert the face geometry of CAD mesh to valid NURBSPatch instances
/// The constructor converts the surface to a clamped (non-periodic) representation, if necessary
class PatchProcessor
{
Expand All @@ -142,8 +142,8 @@ class StepFileProcessor

const opencascade::handle<Geom_BSplineSurface>& getSurface() const { return m_surface; }

/// Returns a representation of the surface as an axom::primal::NURBSPatch
NPatch nurbsPatch() const
/// Returns a representation of the surface geometry as an axom::primal::NURBSPatch
NPatch nurbsPatchGeometry() const
{
// Check if the surface is periodic in u or v
const bool isUPeriodic = m_surface->IsUPeriodic();
Expand Down Expand Up @@ -679,7 +679,13 @@ class StepFileProcessor

PatchProcessor patchProcessor(bsplineSurface, m_verbose);

patches[patchIndex] = patchProcessor.nurbsPatch();
patches[patchIndex] = patchProcessor.nurbsPatchGeometry();

// If the face is flipped in opencascade, we need to flip the primal primitive too
if(face.Orientation() == TopAbs_REVERSED)
{
patches[patchIndex].reverseOrientation_u();
}

PatchData& patchData = m_patchData[patchIndex];
patchData.patchIndex = patchIndex;
Expand Down Expand Up @@ -931,24 +937,10 @@ class StepFileProcessor
}
}

// Ensure that the trimming curves form ccw loops
if(patch.isTrimmed())
// If the face is flipped, then the trimming curves all need to be reversed too
if(TopoDS::Face(faceExp.Current()).Orientation() == TopAbs_Orientation::TopAbs_REVERSED)
{
// Evaluate the signed area over the patch trimming curves
constexpr int n_quad_pts = 20;
auto area = primal::evaluate_vector_line_integral(
patch.getTrimmingCurves(),
[](PointType x) -> VectorType {
return primal::Vector<double, 2>({-0.5 * x[1], 0.5 * x[0]});
},
n_quad_pts);

// Signed areas should be positive
if(area < 0)
{
patch.reverseOrientation_u();
patch.reverseTrimmingCurves();
}
patch.reverseTrimmingCurves();
}
}
}
Expand Down Expand Up @@ -1147,6 +1139,8 @@ class PatchTriangulator
{
TopoDS_Face face = TopoDS::Face(faceExp.Current());

const bool isReversed = (face.Orientation() == TopAbs_Orientation::TopAbs_REVERSED);

// Create a triangulation of this patch
TopLoc_Location loc;
opencascade::handle<Poly_Triangulation> triangulation = BRep_Tool::Triangulation(face, loc);
Expand All @@ -1167,6 +1161,11 @@ class PatchTriangulator
int n1, n2, n3;
triangle.Get(n1, n2, n3);

if(isReversed)
{
std::swap(n1, n3);
}

gp_Pnt p1 = triangulation->Node(n1).Transformed(trsf);
gp_Pnt p2 = triangulation->Node(n2).Transformed(trsf);
gp_Pnt p3 = triangulation->Node(n3).Transformed(trsf);
Expand Down Expand Up @@ -1200,6 +1199,8 @@ class PatchTriangulator
{
TopoDS_Face face = TopoDS::Face(faceExp.Current());

const bool isReversed = (face.Orientation() == TopAbs_Orientation::TopAbs_REVERSED);

// Get the underlying surface of the face
opencascade::handle<Geom_Surface> surface = BRep_Tool::Surface(face);

Expand Down Expand Up @@ -1237,6 +1238,11 @@ class PatchTriangulator
int n1, n2, n3;
triangle.Get(n1, n2, n3);

if(isReversed)
{
std::swap(n1, n3);
}

gp_Pnt p1 = triangulation->Node(n1).Transformed(trsf);
gp_Pnt p2 = triangulation->Node(n2).Transformed(trsf);
gp_Pnt p3 = triangulation->Node(n3).Transformed(trsf);
Expand Down