Wrong calculation with faceVertexCount?

[SamuelReithmeir]

I just stumbled over a problem with FaceVertexCount, i get an invalid memory access.
A sample would be:
face0: 3 vertices
face1: 4 vertices
face2: 5 vertices
this results in a total IndexCount of 12

when adding that mesh declaration i get a invalid memory access (i use XAtlas in c# using swig).
After looking at the code i found this code:

xatlas/source/xatlas/xatlas.cpp

Line 9096 in f700c77

polygon[i] = DecodeIndex(meshDecl.indexFormat, meshDecl.indexData, meshDecl.indexOffset, face * faceVertexCount + i);

According to my understanding face * faceVertexCount + i seems to be a logic error. To explain:
This seems to calculate the offset/beginning of the indices of this face and add i. But the problem is that it assumes that all faces before also have the same faceVertexCount, which destroys the entire purpose of having faceVertexCount be an array in the first place.

Please correct me if i misunderstand the logik here, but i will provide a PR, which will change the logic here to a variable which will sum up the previous faceVertexCounts.

[mifth]

I've created a pull request which should fix the issue. #138

[SamuelReithmeir]

Better fixed by #138

[mifth]

Thanks a lot. I'll continue this thread. I've found another one issue. NGon is gnored if it's too polygonal. If NGon has at least one zero area triangle it will be ignored.

A problem is here. I'm checking it.

[mifth]

This has worked out. We need to calculate an area of all triangles. And then make a decision if it should be ignored.

Now it works well even with a 10000 NGon.

I'll update my pull request.

[mifth]

Another one problem is found: XAtlas triangulates Quads/NGons and considers them as uniquee triangles. For example, 2 triangles of a quad can be in different charts.

This doesn't happen if an original mesh is triangulated:

[mifth]

I think it can be fixed in the computeCharts() function. Looking at it.

[mifth]

It was pretty hard to understand what's going on there but I almos fixed quads and ngons determination by charts. Hopefully, to finish today/tomorrow.

[mifth]

Finally, I made've final changes/fixes for Quads/NGons.

My commit:
22f4d64
#138 (comment)

Pictures:
Some pictures of a final result after a generation:

[mifth]

Some pictures to explain a new computeBoundaryIntersection variable which I've added with the latest commit.