Hi,

I have a simple polysoup mesh of a Triangular Dipyramid <http://polyhedra.org/poly/show/56/triangular_dipyramid [polyhedra.org]>

When I iterate the faces, I get vertex count of 4 instead of the expected 3. Ideas ?

Number of vertices is the expected == 5

npolys = prim->getPolygonCount(); // npolys == 6
// std::cerr << “ArnoldGUDetailVisitor::processPrimPolySoup() npolys = ” << npolys << std::endl;
for (GA_Size polygonIndex = 0; polygonIndex < npolys; polygonIndex++)
{
GA_Size start, count;
prim->getPolygonVertexRange(polygonIndex, start, count);

// Expecting count == 3

for (GA_Size verticesIndex = 0; verticesIndex < count; verticesIndex++)
{
GA_Offset offset = prim->getPolygonVertexOffset(polygonIndex,verticesIndex);

// Expecting offset == 3
vertices.push_back(offset);
}
nvertices.push_back(count);
nloops.push_back(1);
}

Cheers

Here is the code and output showing the iterator showing duplicate vertices

GU_PrimPolySoup * polysoup = dynamic_cast<GU_PrimPolySoup*>(gprim);
if (polysoup)
{
GEO_Detail *detail = polysoup->getParent();
if (detail)
{
for (GEO_PrimPolySoup:olygonIterator it(*polysoup); !it.atEnd(); ++it)
{
printf(“Face: [”);
for (GEO_PrimPolySoup::VertexIterator vit(it); !vit.atEnd(); ++vit)
{
GA_Offset ptoff = detail->vertexPoint(vit.offset());
UT_Vector3 P = detail->getPos3(ptoff);
printf(“{%g,%g,%g},”, P.x(), P.y(), P.z());
}
printf(“]\n”);
}
}
}


Here is the print out of the duplicates

Face:
Face:
Face:
Face:
Face:
Face:


Cheers

Here is a printout with the ptoff value

There is a repetition of the index offset.

Should I be filtering out the duplicates or is that inherent in the polysoup design?

Face: [
(ptoff = 0) => {2.18557e-08,1,-3.78552e-08}
(ptoff = 0) => {2.18557e-08,1,-3.78552e-08}
(ptoff = 3) => {-0.5,0,-0.866025}
(ptoff = 2) => {1,0,0}
]
Face: [
(ptoff = 0) => {2.18557e-08,1,-3.78552e-08}
(ptoff = 0) => {2.18557e-08,1,-3.78552e-08}
(ptoff = 4) => {-0.5,0,0.866025}
(ptoff = 3) => {-0.5,0,-0.866025}
]
Face: [
(ptoff = 0) => {2.18557e-08,1,-3.78552e-08}
(ptoff = 0) => {2.18557e-08,1,-3.78552e-08}
(ptoff = 2) => {1,0,0}
(ptoff = 4) => {-0.5,0,0.866025}
]
Face: [
(ptoff = 2) => {1,0,0}
(ptoff = 3) => {-0.5,0,-0.866025}
(ptoff = 1) => {2.18557e-08,-1,-3.78552e-08}
(ptoff = 1) => {2.18557e-08,-1,-3.78552e-08}
]
Face: [
(ptoff = 3) => {-0.5,0,-0.866025}
(ptoff = 4) => {-0.5,0,0.866025}
(ptoff = 1) => {2.18557e-08,-1,-3.78552e-08}
(ptoff = 1) => {2.18557e-08,-1,-3.78552e-08}
]
Face: [
(ptoff = 4) => {-0.5,0,0.866025}
(ptoff = 2) => {1,0,0}
(ptoff = 1) => {2.18557e-08,-1,-3.78552e-08}
(ptoff = 1) => {2.18557e-08,-1,-3.78552e-08}
]

I have found that enabling the “convex” parameter in the polysoup SOP eliminated the duplicate vertices but am unsure if that is the correct approach or proper solution.

nicholas_yue
I have found that enabling the “convex” parameter in the polysoup SOP eliminated the duplicate vertices but am unsure if that is the correct approach or proper solution.

Check the vertex count from before converting to PolySoup. If it's 24, you have quads that just happen to have the same point twice. PolySoups are supposed to be an exact representation of the original polygons. The polygons might not be in the same order, but the content should be identical.

Convexing probably isn't what you want to do to fix this, because you'll end up with 12 triangles (6 of them degenerate) instead of the 6 you want.