KHR_mesh_quantization input mesh , brings wrong indexed indexed triangle mesh

[arpu]

hi,

i have meshopt input mesh and with GltfLoader set with loader.setMeshoptDecoder(MeshoptDecoder); i get the uncompressed mesh but still with KHR_mesh_quantization and the generated navMesh is wrong.

there is a https://gltf-transform.dev/modules/functions/functions/dequantize in gltf-tranform but want to ask if i need this?

[isaac-mason]

Hi @arpu, you can find the logic that's used by the threejs lib and navmesh generator website to transform threejs meshes to positions and indices here:

• /~https://github.com/isaac-mason/recast-navigation-js/blob/main/packages/recast-navigation-three/src/utils/get-positions-and-indices.ts#L56
• /~https://github.com/isaac-mason/recast-navigation-js/blob/main/packages/recast-navigation-generators/src/generators/merge-positions-and-indices.ts#L1

It may be that getPositionsAndIndices needs a simple fix to correctly parse quantized meshes if e.g. the position attribute is not a Float32Array, or something else.

[arpu]

Hey @isaac-mason Thanks for the infos!

looks like the proplem is not the quantized, its the interleaved BufferAttributes
/~https://github.com/isaac-mason/recast-navigation-js/blob/main/packages/recast-navigation-three/src/utils/get-positions-and-indices.ts#L15

updating with

  let positionAttribute = mesh.geometry.attributes.position;
                 if (positionAttribute.isInterleavedBufferAttribute) {
                    // Deinterleave the attribute
                  
                    positionAttribute = deinterleaveAttribute(positionAttribute);
                   mesh.geometry.setAttribute('position', positionAttribute);

                   
                }

works for me