Porting glTF reference renderer code to Vulkan

[JoshKlint]

I’ve had great results integrating the sample viewer code here into my own engine:

GitHub - KhronosGroup/glTF-Sample-Viewer: Physically-Based Rendering in glTF...

However, I am having trouble with the sheen fabric material in the Toycar sample. This is what it should look like:

My renderer is showing a weird specular highlight on edges:

Here is just the default metal/roughness reflection without the sheen factor. (The highlights you are seeing move around with the camera position and look sort of like satin material):

And these are the lookup tables I am using:

The cubemaps are generated with this tool:

GitHub - KhronosGroup/glTF-IBL-Sampler: Sampler to create the glTF sample...

Has anyone seen this effect before? Any idea why this would be happening? I’ve barely touched the default shader code. My metal/roughness values all match the debug views of the reference renderer.

[JoshKlint]

It appears this may be the cause:

How to generate Sheen E LUT

I am trying to generate some new IBL environments using glTF-IBL-Sampler (because the KTX2 textures in glTF-Sample-Environments won’t load with the latest KTX-Software/libktx as they appear to be an outdated format). I can get this to work, I compiled the source myself and the results look great. However I have one question. My shaders are mostly just slight modifications of the shaders in the glTF-Sample-Viewer and there is one LUT texture that I am basically just pulling from the sample viewe…

[JoshKlint]

Here is what it looks like in motion:

glTF sheen bug

[JoshKlint]

I actually found this was caused because I forgot to clamp my lookup textures.