GenerateTangents in 0.14.1 can panic even though it is supposed to return Result

[ethereumdegen]

Bevy version

0.14.1

What went wrong

MESH:: GenerateTangents() in 0.14.1 can panic even though it is supposed to return Result

 thread 'Compute Task Pool (1)' panicked at /home/andy/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bevy_mikktspace-0.14.0/src/generated.rs:1033:15:
attempt to subtract with overflow
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Encountered a panic in system `bevy_clay_tiles::clay_tile_block::build_tile_block_meshes`!

[rparrett]

Are you able to provide the mesh that is causing this panic?

[ethereumdegen]

not easily no because it could be one of many and it was one generated by a procgen mesh algo :(

this algo https://github.com/ethereumdegen/bevy_clay_tiles/blob/master/src/pre_mesh.rs

[rparrett]

Even a println!("{:?}", mesh) would probably be useful.

[ethereumdegen]

{ primitive_topology: TriangleList, attributes: {MeshVertexAttributeId(0): MeshAttributeData { attribute: MeshVertexAttribute { name: "Vertex_Position", id: MeshVertexAttributeId(0), format: Float32x3 }, values: Float32x3([[0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0]]) }, MeshVertexAttributeId(1): MeshAttributeData { attribute: MeshVertexAttribute { name: "Vertex_Normal", id: MeshVertexAttributeId(1), format: Float32x3 }, values: Float32x3([[0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0]]) }, MeshVertexAttributeId(2): MeshAttributeData { attribute: MeshVertexAttribute { name: "Vertex_Uv", id: MeshVertexAttributeId(2), format: Float32x2 }, values: Float32x2([[0.0, 1.0], [0.0, 0.0], [0.0, 1.0], [0.0, 1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 1.0], [0.0, 0.0], [0.0, 1.0], [0.0, 1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 1.0], [0.0, 0.0], [0.0, 1.0], [0.0, 1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 1.0], [0.0, 0.0], [0.0, 1.0], [0.0, 1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 1.0], [0.0, 0.0], [0.0, 1.0], [0.0, 1.0], [0.0, 0.0], [0.0, 0.0]]) }}, indices: Some(U32([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29])), morph_targets: None, morph_target_names: None, asset_usage: RenderAssetUsages(MAIN_WORLD | RENDER_WORLD) }
thread 'Compute Task Pool (1)' panicked at /home/andy/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bevy_mikktspace-0.14.0/src/generated.rs:1033:15:
attempt to subtract with overflow
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Encountered a panic in system `bevy_clay_tiles::clay_tile_block::build_tile_block_meshes`!

[kumikaya]

The panic occurs in the function bevy_mikktspace::generated::genTangSpace due to a scenario where the number of valid triangles (iNrTrianglesIn) becomes zero after degenerate triangle detection and removal. This leads to the InitTriInfo function being called with zero triangles, causing a panic.