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Tugcga / Softimage-GLTF-IO

Softimage addon for import and export gltf/glb files
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Fails to import Buggy sample model #2

Open Tugcga opened 1 year ago

Tugcga commented 1 year ago

When I try to import Buggy sample model, the Softimage is crashed.

It imports some materials and geometry, but crashed with errors in the middle of the process. Why it happens?

ReinhardC commented 1 year ago

Debugging the app, I run into an exception here import_mesh.cpp line 549

Exception thrown at 0x00000000151713A7 (mogeometry.dll) in XSI.exe: 0xC0000005: Access violation writing location 0x00000001E7075A50.

cluster.SetValues(attr_data.data(), samples_start_index);

samples_start_index seems too large for the Normal Cluster.

cluster.SetValues(attr_data.data(), cluster.GetElements().GetCount());

avoids the crash but some normals are bad for about half of the objects. I'll try investigating a bit further.

ReinhardC commented 1 year ago

I think the buggy model just might be broken, it reports sometimes more normals than the object has samples in its cluster. I would suggest to do a check (samples_start_index == xsi_mesh.GetSamples().GetCount()) and if that fails, not import that cluster data.

Tugcga commented 1 year ago

Ok, I thought something like that. May be I will implement this solution.

Tugcga commented 1 year ago

Finally I found the problem. It turns out that meshes in Buggy sample contains trivial triangles. These triangles span three vertices, where two of them are the same. When I build the mesh in Softimage by using

XSI::CMeshBuilder mesh_builder;
mesh_builder.AddVertices(vertex_count, positions.data());
mesh_builder.AddPolygons(triangles_count, polygon_sizes.data(), triangles.data());
mesh_builder.Build(false);

then the Softimage ignores these trivial triangles. As a result the actual number of samples in the generated mesh is less than the number of normals in the input gltf-file. So, the Softimage is fails to assign a big array with normals to the cluster with smaller size.

ReinhardC commented 1 year ago

Nice job . I updated it here: si-community.com/community/resources.php (Let me know in case you want some changes to your listings)