Wrap getIBLContribution with #ifdef USE_IBL

[Lunarsong]

Without this the shader may fail compilation because the uniforms used in the getIBLContribution function are not being declared.

[emackey]

Thanks @Lunarsong. Do you want to wrap uniform vec4 u_ScaleIBLAmbient; in that as well?

[Lunarsong]

I'm not sure. How will it affect the stuff on the main.js? My web dev is quite weak so I honestly don't know :) I noticed the shader issue when using it locally in a C program.

I see main.js is referencing u_ScaleIBLAmbient in lines 200 and 282. Is it going to be happy with them removed?
https://github.com/KhronosGroup/glTF-WebGL-PBR/blob/c28b5b8f5a83380857ad8395ac5302594ecc13ae/main.js#L200

Unlike the function which used the missing sampler, keeping these uniforms in won't break compilation.

[emackey]

@Lunarsong You're right, the web side isn't set up to actually remove IBL like that. We'll take this as-is, thanks!

If you're building anything cool with glTF that you're allowed to talk about, please let us know!

[Lunarsong]

Thanks for merging! I'm working on a game, but it's a side project while maintaining full time job... Hope to get enough progress to share more :) Where should I mention it?

[emackey]

We've been tracking the latest glTF projects in KhronosGroup/glTF#1058. Finished projects are intended to end up in the main README.md.

[Lunarsong]

Thanks! :)