[WIP] per channel uv transform example

[pailhead]

I mustered up a quick example to override the vUv value in the shaders.

http://dusanbosnjak.com/test/webGL/three-materials-extended/webgl_materials_extended_multiple_uvs_props.html

I used roughnessMap, specularMap, metalnessMap and map and added a simple scale + offset to each.

It's not the cleanest thing but it's an example of how to quickly prototype something without affecting the core.

#14149
#12788
#12608
#13831
#8278
#5876

It's easy to also expose these, but for some reason i think onBeforeCompile fired twice. I actually tried to mimick onAfterParse because onBeforeCompile is also onBeforeParse.

This is another example of using shader injection, specifically with the currently available onBeforeCompile. I think it's trivial to solve issues such as the ones linked with this kind of an api. However, i think there are better alternatives to it:

#13198

I think that this is a valid use case to find itself in the core, (transforms probably don't belong on textures, rather texture slots) but since it's a complicated process to propose and review something like that, onBeforeCompile allows for quick prototyping.

In this particular case, it mimicked a script that one could write to replace some code over many files, rather than doing it manually. For production it's a bit clunky, that's where i'd propose an alternative. Even if this weren't in the core, i think the area of GLSL is so self contained that this would be an easy effect to carry across and combine with other shader modifications.

[pailhead]

v3 copies the transform matrix logic, i also moved the uniform creation to be synchronous.

http://dusanbosnjak.com/test/webGL/three-materials-extended/webgl_materials_extended_multiple_uvs_props_transform.html

[WestLangley]

It took me awhile to step through this example, but it does show one way to use onBeforeCompile() to support different transforms per material texture.

I understand this to be a feasibility study. We would not expect users to do this, obviously.

[pailhead]

Why not if it is encapsulated somehow?

The user only sees this:

myMaterial.specularMap       //Texture
myMaterial.specularMapOffset //Vector2
myMaterial.specularMapRepeat //Vector2
myMaterial.specularMapRotate //Number
myMaterial.specularMapUpdateMatrix // function

Maybe

myMaterial.specularMap
myMaterial.specularMapTransform = {
  offset,
  repeat,
  rotate,
  update,
}

Advanced user sees example how to make this ^

[mrdoob]

#14245 (comment)

[VrTech]

@pailhead
Can it also work with a normal map? I really struggle with this.