3D Model stopped rendering after upgrading to v1.75

[dzungpng]

Sandcastle example: link.

Browser: Chrome

Operating System: Windows 10

What the model supposed to look like:

What it looks like with v1.75:

The breaking commit is #9173 (@lilleyse).

This is a .glb model.

[lilleyse]

I think there's a bug in the glTF model itself that is being exposed by the change in #9173.

This is one of the attribute accessors from the source .glb

{
  "bufferView":7,
  "componentType":5125,
  "count":2145,
  "type":"SCALAR",
  "min":[4],
  "max":[4]
}

which isn't isn't valid according to the glTF spec:

"gltf_detailedDescription": "The datatype of components in the attribute. All valid values correspond to WebGL enums. The corresponding typed arrays are Int8Array, Uint8Array, Int16Array, Uint16Array, Uint32Array, and Float32Array, respectively. 5125 (UNSIGNED_INT) is only allowed when the accessor contains indices, i.e., the accessor is only referenced by primitive.indices.",

The glTF validator doesn't seem to catch this and I may need to open a bug report.

One workaround is for the user is to delete the _MaxHandle vertex attribute from the "attributes" object in the glTF and then re-upload to ion.

The reason this breaks now is that #9173 allowed unused attributes to be added to the vertex array because an unused attribute at time of vertex array creation might be used when a material is applied. But now a faulty attribute is slipping through and failing on the gl.vertexAttribPointer command because 5125 is not a valid type.

[emackey]

The glTF validator doesn't seem to catch this and I may need to open a bug report.

Are there any glTF extensions in use here? If not please file an issue, thanks!

[lilleyse]

@emackey no extensions. Just opened the issue: KhronosGroup/glTF-Validator#154

[emackey]

Awesome thanks!

[emackey]

From my perspective, this is an invalid glTF file, not a bug in Cesium. It should be corrected in the model itself.

[hpinkos]

Agreed. @dzungpng could you pass this information along to the person that reported the issue?