TextureEncodingTest.gltf is different from expected result

[cx20]

Describe the bug

I tried Khronos' new test model TextureEncodingTest.gltf with Three.js.
However, it seems to be different from the expected result.

To Reproduce

Three.js r125 + TextureEncodingTest.gltf result:

Expected behavior

Platform:

• Device: MacBook Air
• OS: Windows 10 (BootCamp)
• Browser: Chrome 88.0.4324.182
• Three.js version: r125

[donmccurdy]

For our reference, more details on this test here: KhronosGroup/glTF-Sample-Models#296

[takahirox]

It seems custom gamma and icc profiles embedded in image file should be ignored in glTF.

https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#images

Any colorspace information (such as ICC profiles, intents, etc) from PNG or JPEG containers must be ignored. Effective transfer function is defined by a glTF object that refers to the image.

https://github.com/KhronosGroup/glTF-Sample-Models/tree/encoding/2.0/TextureEncodingTest#description

Additionally, this asset tests that gamma values and/or ICC profiles embedded with image files are ignored as the glTF spec requires.

So, we need to turn off color space conversion for glTF.

GLTFLoader uses ImageBitmap if it's available. Color space conversion needs to be specified at ImageBitmap creation then I locally added this.textureLoader.setOptions( { colorSpaceConversion: 'none' } ); after this.textureLoader = new ImageBitmapLoader( this.options.manager ) in GLTFLoader and the result looks correct.

For platforms where ImageBitmap is not available GLTFLoader uses regular TextureLoader. In this case color space conversion needs to be specified at texture uploading with gl.pixelStorei() but currently WebGLRenderer doesn't manage gl.UNPACK_COLORSPACE_CONVERSION_WEBGL then we may need to add a new property for color space conversion to Texture like Texture.colorSpaceConversion (BROWSER_DEFAULT_WEBGL or None) and the renderer calls gl.pixelStorei(gl.UNPACK_COLORSPACE_CONVERSION_WEBGL, texture.colorSpaceConversion).

[takahirox]

I made two PRs #21323 and #21324 which resolve this issue.