Nice, and a suggestion on alpha cutouts

[erich666]

This viewer works fairly well. It does have a problem with cutout images, evidently turning off the z-buffer when these are rendered. I recommend a "clamp" shader that draws to the z-buffer when the alpha test is greater than say 0.01. See https://stackoverflow.com/questions/24302152/opengl-alpha-test-how-to-replace-alphafunc-deprecated/24312267 for example.

Here's what it looks like in the viewer:

Here's what's expected:

Here's the test file set: azalea_test.zip

Model downloaded from here: https://skfb.ly/o7xsS

Best of luck figuring out a solution and keep up the nice work!

[donmccurdy]

Hi Eric! glTF identifies alpha cutout and alpha blending as two distinct "modes", and in this case the material itself selects alpha blending. The z-buffer is turned off only in that case, and won't be disabled where alpha cutout is indicated.

I guess that's probably an issue in the Sketchfab download, but a quick way to diagnose and fix would be:

1. Open model on https://gltf.report/
2. Check material settings:
3. Convert to "MASK" mode in script panel:

   for (const mat of document.getRoot().listMaterials()) {
   if (mat.getAlphaMode() === 'BLEND') {
       mat.setAlphaMode('MASK')
          .setAlphaCutoff(0.01);
   }
   }

Result:

[erich666]

Ah, thanks, sounds like a Sketchfab bug, or one where I (I maintain Mineways) need to hint them more as to whether the texture is applied as a cutout or as opacity - I'll try reporting it to them.

Yeah, if it's opacity, you then have to deal with the usual z-buffer limitation that rasterization has. Some decade we'll all be ray tracing everything and it won't then matter. :)

[donmccurdy]

I'm almost positive I have seen a model from Sketchfab that did use alpha cutout, so I do think there's a way... no idea what that would be though sorry!