GLTF Importer does NOT work for JointIndices and JointWeight

[HanetakaChou]

When I load one GLTF asset, the jointStride and weightStride can be zero!

We should change the stride manually, just like how we calcualte the indexStride when importing the IndexBuffer.

            if (joint_indices)
            {
                assert(joint_indices->count == positions->count);

                auto [jointSrc, jointStride] = cgltf_buffer_iterator(joint_indices, 0);
                vector<uint16_t, 4>* jointDst = buffers->jointData.data() + totalVertices;

                if (joint_indices->component_type == cgltf_component_type_r_8u)
                {
                    // !!! This line is what I add.
                    if (!jointStride) jointStride = sizeof(uint8_t) * 4;

                    for (size_t v_idx = 0; v_idx < joint_indices->count; v_idx++)
                    {
                        *jointDst = dm::vector<uint16_t, 4>(jointSrc[0], jointSrc[1], jointSrc[2], jointSrc[3]);

                        jointSrc += jointStride;
                        ++jointDst;
                    }
                }
                else
                {
                    assert(joint_indices->component_type == cgltf_component_type_r_16u);

                    // !!! This line is what I add.
                    if (!jointStride) jointStride = sizeof(uint16_t) * 4;

                    for (size_t v_idx = 0; v_idx < joint_indices->count; v_idx++)
                    {
                        const uint16_t* jointSrcUshort = (const uint16_t*)jointSrc;
                        *jointDst = dm::vector<uint16_t, 4>(jointSrcUshort[0], jointSrcUshort[1], jointSrcUshort[2], jointSrcUshort[3]);

                        jointSrc += jointStride;
                        ++jointDst;
                    }
                }
            }

            if (joint_weights)
            {
                assert(joint_weights->count == positions->count);

                auto [weightSrc, weightStride] = cgltf_buffer_iterator(joint_weights, 0);
                float4* weightDst = buffers->weightData.data() + totalVertices;

                if (joint_weights->component_type == cgltf_component_type_r_8u)
                {

                    // !!! This line is what I add.
                    if (!weightStride) weightStride = sizeof(uint8_t) * 4;

                    for (size_t v_idx = 0; v_idx < joint_indices->count; v_idx++)
                    {
                        *weightDst = dm::float4(
                            float(weightSrc[0]) / 255.f,
                            float(weightSrc[1]) / 255.f,
                            float(weightSrc[2]) / 255.f,
                            float(weightSrc[3]) / 255.f);

                        weightSrc += weightStride;
                        ++weightDst;
                    }
                }
                else if (joint_weights->component_type == cgltf_component_type_r_16u)
                {

                    // !!! This line is what I add.
                    if (!weightStride) weightStride = sizeof(uint16_t) * 4;

                    for (size_t v_idx = 0; v_idx < joint_indices->count; v_idx++)
                    {
                        const uint16_t* weightSrcUshort = (const uint16_t*)weightSrc;
                        *weightDst = dm::float4(
                            float(weightSrcUshort[0]) / 65535.f,
                            float(weightSrcUshort[1]) / 65535.f,
                            float(weightSrcUshort[2]) / 65535.f,
                            float(weightSrcUshort[3]) / 65535.f);
                        
                        weightSrc += weightStride;
                        ++weightDst;
                    }
                }
                else
                {
                    assert(joint_weights->component_type == cgltf_component_type_r_32f);

                    // !!! This line is what I add.
                    if (!weightStride) weightStride = sizeof(float) * 4;

                    for (size_t v_idx = 0; v_idx < joint_indices->count; v_idx++)
                    {
                        *weightDst = (const float*)weightSrc;

                        weightSrc += weightStride;
                        ++weightDst;
                    }
                }
            }

[HanetakaChou]

Here is the Pull Request!

[HanetakaChou]

@apanteleev

[HanetakaChou]

Here is the glTF Validator output of my glTF asset (NO ERROR! NO WARNING!):

{
    "uri": "/sparkle.gltf",
    "mimeType": "model/gltf+json",
    "validatorVersion": "2.0.0-dev.3.10",
    "validatedAt": "2024-11-04T21:46:11.944Z",
    "issues": {
        "numErrors": 0,
        "numWarnings": 0,
        "numInfos": 0,
        "numHints": 0,
        "messages": [],
        "truncated": false
    },
    "info": {
        "version": "2.0",
        "generator": "Khronos glTF Blender I/O v4.2.70",
        "resources": [
            {
                "pointer": "/buffers/0",
                "mimeType": "application/gltf-buffer",
                "storage": "external",
                "uri": "sparkle.bin",
                "byteLength": 3393892
            },
            {
                "pointer": "/images/0",
                "mimeType": "image/png",
                "storage": "external",
                "uri": "clothing.png",
                "image": {
                    "width": 2048,
                    "height": 1024,
                    "format": "rgb",
                    "primaries": "srgb",
                    "transfer": "srgb",
                    "bits": 8
                }
            },
            {
                "pointer": "/images/1",
                "mimeType": "image/png",
                "storage": "external",
                "uri": "hair.png",
                "image": {
                    "width": 1024,
                    "height": 1024,
                    "format": "rgb",
                    "primaries": "srgb",
                    "transfer": "srgb",
                    "bits": 8
                }
            },
            {
                "pointer": "/images/2",
                "mimeType": "image/png",
                "storage": "external",
                "uri": "face.png",
                "image": {
                    "width": 512,
                    "height": 512,
                    "format": "rgb",
                    "primaries": "srgb",
                    "transfer": "srgb",
                    "bits": 8
                }
            },
            {
                "pointer": "/images/3",
                "mimeType": "image/png",
                "storage": "external",
                "uri": "eye.png",
                "image": {
                    "width": 256,
                    "height": 256,
                    "format": "rgba",
                    "primaries": "srgb",
                    "transfer": "srgb",
                    "bits": 8
                }
            },
            {
                "pointer": "/images/4",
                "mimeType": "image/png",
                "storage": "external",
                "uri": "expression.png",
                "image": {
                    "width": 1024,
                    "height": 1024,
                    "format": "rgba",
                    "primaries": "srgb",
                    "transfer": "srgb",
                    "bits": 8
                }
            }
        ],
        "animationCount": 1,
        "materialCount": 5,
        "hasMorphTargets": false,
        "hasSkins": true,
        "hasTextures": true,
        "hasDefaultScene": true,
        "drawCallCount": 5,
        "totalVertexCount": 23551,
        "totalTriangleCount": 30122,
        "maxUVs": 1,
        "maxInfluences": 4,
        "maxAttributes": 5
    }
}

But donut does not work properly on my asset due to the incorrect jointStirde and weightStride.

[apanteleev]

Pull request merged, closing the issue.
Thanks @HanetakaChou !