Helper to deal with multi-materials

Description of the problem

I am currently merging meshes with different materials which result in a single mesh with material property being an array.

Then I had to update all my code base in order to support this, and I feel like repeating myself a LOT !

That’s why I think it might be cool to have something to help us dealing with that.

I don’t think forcing material to be an array is a good move because of the memory overhead it will add.

I am thinking on a stuff more like this:

forEachMaterial(callback) {
  if (Array.isArray(this.material)) {
     for( var i =0; l = this.material.length; i < l; i++ ){
        callback(this.material[i]);
    }
  } else {
     callback(this.material);
  }
}

Like this on my side I could replace

if (Array.isArray(mesh.material)) {
     for( var i =0; l = this.material.length; i < l; i++ ){
        material[i].opacity = 0.5;
    }
} else {
  material.opacity = 0.5;
}

By

mesh.forEachMaterial(function(material) {
  material.opacity = 0.5;
});

[WestLangley]

I am currently merging meshes with different materials which result in a single mesh with material property being an array.

Why not merge only meshes that share a single material? Only one material can be rendered in a draw call, so if you have N materials, you will have N draw calls anyway – and maybe many more than that if your merged faces are not properly sorted.

[WestLangley]

@moroine I think that makes sense.