MaterialLoader:createMaterial() for extended Material class

[sunag]

Description

The function MaterialLoader.createMaterial( type ) can be useful to create loader for extended Materials, like NodeMaterials.

Example:

class NodeMaterialLoader extends MaterialLoader {

	constructor( manager ) {

		super( manager );

	}

	createMaterial( type ) {

		// use an extended material if here is

		if ( NodeMaterial[ type ] !== undefined ) {

			return new NodeMaterial[ type ]();

		}

		return super.createMaterial( type );

	}

	parse( json ) {

		const material = super.parse( json );

		// stuff

		return material;

	}

}

This contribution is funded by Google via Igalia.

[mrdoob]

How about adding this to Material.js as a static class instead?

const material = Material.fromType( type );

[sunag]

This look a bit more complicated to extended using only Material.fromType(). For example, without MaterialLoader.createMaterial() is possible to replace the prototype, something like:

Material.prototype._fromType = Material.prototype.fromType;

Material.prototype.fromType = ( type ) => {

	if ( NodeMaterialLib[ type ] !== undefined ) {

		return new NodeMaterialLib[ type ]();

	}

	return Material.prototype._fromType( type );

}

[sunag]

@mrdoob I can do like this, if you to prefer:

const materialLoader = new MaterialLoader();

 // material lib
materialLoader.library = Materials;

materialLoader.parse( json );

[sunag]

Current PR:

const materialLoader = new NodeMaterialLoader();
materialLoader.parse( json );

[mrdoob]

This look a bit more complicated to extended using only Material.fromType(). For example, without MaterialLoader.createMaterial() is possible to replace the prototype, something like:

Material.prototype._fromType = Material.prototype.fromType;

Material.prototype.fromType = ( type ) => {

	if ( NodeMaterialLib[ type ] !== undefined ) {

		return new NodeMaterialLib[ type ]();

	}

	return Material.prototype._fromType( type );

}

That doesn't look too bad. How about creating a NodeMaterial class too?
Probably doesn't need to extend Material?

[sunag]

Probably doesn't need to extend Material?

The problem is that the Materials lib is readonly inside parse():
Currently, It creates only the root materials and not allows being extended.

three.js/src/loaders/MaterialLoader.js

Line 70 in 64f9b32

const material = new Materials[ json.type ]();

[sunag]

I am developing a version using Material.fromType()...

[sunag]

Seems that is not possible import Materials.js inside Material because has redundancy cycle of imports. So I created MaterialUtils.fromType(). What do you think?

[sunag]

How about creating a NodeMaterial class too?

I will try to mature this then. If we use a NodeMaterial as root node materials, an extension of MaterialLoader for NodeMaterial like this PR lost sense.

[sunag]

I am thinking about close this PR because extending the current NodeMaterials for a NodeMaterial base made the things a bit different and better in my option. In this context extend the MaterialLoader is not so more necessary. Anyway, we can a wait a little until that I can publish the PR related to close this.

[sunag]

@mrdoob I still have some issue with this, exist some possibilities here that I noticed:

1. Add Material.fromType() in Material.js result in Circular depedencies I can add this in other file to fix it, for example: MateiralUtils.js.
2. Use .fromType() in other class MaterialUtils.fromType().
3. Use MaterialLoader.createMaterial().
4. Use library variable in MaterialLoader: materialLoader.library = MaterialsLib