glb/gltf files import fails if extension in `extensionsRequired` list is not present

[SeaOtocinclus]

"Regression with the Asset3D support"

• 3D models that use to load, can't be loaded with new versions, despite being GLTF compliant

To Reproduce

Try to load the mesh "5462893327580.glb" shared here
5462893327580.glb.zip

v0.16 -> Can load
v0.17/0.18 -> Can't load

WARN  re_space_view_spatial::mesh_cache] Failed to load mesh "5462893327580": invalid glTF: extensionsRequired[0] = "KHR_texture_transform": Unsupported extension;

Expected behavior

• Asset3D should be compliant and be able to load files that respect the format (gltf compliant).
• Files that load for one version, should still load in new versions

[Wumpf]

It look like the gltf loader library we use previously ignored the requiredExtension field of the glb/gltf. The spec mandates that loading fails if a loader doesn't support any of the extensions listed as required by a mesh. So the loader behaves now according to that spec.
That said, obviously all the other data should be able to be loaded so we can at least try to display it, but this requires us to either downgrade (& fix upstream) or change our gltf library.

Meanwhile, you'll have to remove this extension from the required list.

Here's your mesh as GLTF:

{
  "asset": {
    "generator": "glTF-Transform v4.0.0",
    "version": "2.0"
  },
  "accessors": [
    {
      "type": "VEC3",
      "componentType": 5126,
      "count": 2432,
      "max": [
        36.395713806152344,
        4.665484428405762,
        76.97759246826172
      ],
      "min": [
        -36.5335807800293,
        -5.6504364013671875,
        -76.97759246826172
      ],
      "bufferView": 0,
      "byteOffset": 0
    },
    {
      "type": "VEC3",
      "componentType": 5126,
      "count": 2432,
      "bufferView": 0,
      "byteOffset": 12
    },
    {
      "type": "VEC2",
      "componentType": 5126,
      "count": 2432,
      "bufferView": 0,
      "byteOffset": 24
    },
    {
      "type": "SCALAR",
      "componentType": 5123,
      "count": 8091,
      "bufferView": 1,
      "byteOffset": 0
    }
  ],
  "bufferViews": [
    {
      "buffer": 0,
      "byteOffset": 0,
      "byteLength": 77824,
      "byteStride": 32,
      "target": 34962
    },
    {
      "buffer": 0,
      "byteOffset": 77824,
      "byteLength": 16184,
      "target": 34963
    }
  ],
  "samplers": [
    {
      "magFilter": 9728,
      "minFilter": 9984,
      "wrapS": 33071,
      "wrapT": 33071
    },
    {
      "magFilter": 9729,
      "minFilter": 9987,
      "wrapS": 10497,
      "wrapT": 10497
    },
    {
      "magFilter": 9729,
      "minFilter": 9987,
      "wrapS": 33071,
      "wrapT": 33071
    }
  ],
  "textures": [
    {
      "source": 0,
      "sampler": 0
    },
    {
      "source": 2,
      "sampler": 1
    },
    {
      "source": 3,
      "sampler": 1
    },
    {
      "source": 1,
      "sampler": 2
    }
  ],
  "images": [
    {
      "name": "base",
      "uri": "5462893327580_img0.jpg"
    },
    {
      "name": "metallicRoughness",
      "uri": "5462893327580_img1.jpg"
    },
    {
      "name": "normal",
      "uri": "5462893327580_img2.jpg"
    },
    {
      "name": "occlusion",
      "uri": "5462893327580_img3.jpg"
    }
  ],
  "buffers": [
    {
      "uri": "5462893327580_data.bin",
      "byteLength": 94008
    }
  ],
  "materials": [
    {
      "name": "Smartphone_Body_Material",
      "doubleSided": true,
      "pbrMetallicRoughness": {
        "baseColorTexture": {
          "index": 0
        },
        "metallicRoughnessTexture": {
          "index": 3
        }
      },
      "normalTexture": {
        "index": 1,
        "extensions": {
          "KHR_texture_transform": {
            "offset": [
              0.0078119998797774315,
              0.0078125
            ],
            "scale": [
              8.000791549682617,
              15.752901077270508
            ]
          }
        }
      },
      "occlusionTexture": {
        "index": 2,
        "extensions": {
          "KHR_texture_transform": {
            "offset": [
              0.0078119998797774315,
              0.0078125
            ],
            "scale": [
              8.000791549682617,
              15.752901077270508
            ]
          }
        }
      }
    }
  ],
  "meshes": [
    {
      "primitives": [
        {
          "attributes": {
            "POSITION": 0,
            "NORMAL": 1,
            "TEXCOORD_0": 2
          },
          "mode": 4,
          "material": 0,
          "indices": 3
        }
      ]
    }
  ],
  "nodes": [
    {
      "name": "smartphone_xiaomi13_Hot3D",
      "scale": [
        0.0010000000474974513,
        0.0010000000474974513,
        0.0010000000474974513
      ],
      "mesh": 0
    }
  ],
  "scenes": [
    {
      "name": "Scene",
      "nodes": [
        0
      ]
    }
  ],
  "scene": 0,
  "extensionsUsed": [
    "KHR_texture_transform"
  ],
  "extensionsRequired": [
    "KHR_texture_transform"
  ]
}

Notice the last bit: extensionsRequired. If you only specify it as "used" instead of "required", it still loads fine.
Here's the file with this change repacked as glb for illustration purposes:
fixed.glb.zip

Keeping this issue open since Rerun should handle this regardless.

[Wumpf]

• Upstream issue: Allow (partial) load of meshes with unsupported required extensions gltf-rs/gltf#431

[SeaOtocinclus]

Thank you @Wumpf for looking into this and tracing back how I could find a workaround.

[emilk]

From the changelog it looks like we just need to set the allow_empty_texture flag: https://github.com/gltf-rs/gltf/blob/main/CHANGELOG.md

EDIT: no, allow_empty_texture was not enough to fix this

[emilk]

Pinning gltf to =1.4.0 des not solve the issue either, weirdly enough. I think we need to bite the bullet and do a patch to gltf if we want to support loading meshes with errors.