Improved MaterialX import support to align with Blender's MaterialX exporter.

[bhouston]

Description

Adds support for the following MaterialX core nodes:

• ln
• transform matrix
• transpose
• determinant
• invert matrix
• creatematrix
• length
• crossproduct
• ceil
• floor
• place2d
• reflect
• refract
• ifgreater
• ifgreatereq
• ifequal
• rotate2d
• rotate3d
• heighttonormal
• separate
• uniformnoise2d
• uniformnoise3d
• ramp4
• extract

Add support for standard_surface material inputs:

• opacity
• specularIntensity
• specularColor
• ior, anisotropy
• anisotropyRotation
• sheen intensity
• sheen color
• sheen roughness
• thin film thickness
• thin film ior
• transmission
• transmissionColor.

Improved handling of material rendering modes:

• Automatically becomes "transparent" if opacityNode or transmissionNode is defined.
• Automatically becomes DoubleSided is transmissionNode is defined.
• Automatically has iridescence set to 1.0 if thinFilmThicknessNode is defined.

These were motivated by the fact that Blender exports these MaterialX nodes, but ThreeJS doesn't support them.

I've included a bunch of new mtlx example files that demonstrate the new features!

This contribution is funded by DriveCore, Inc.

The new materialx loader example results:

What it looks like before this PR (notice that even the original materials now look better):

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	338.39 78.91	338.39 78.91	+0 B +0 B
WebGPU	561.91 155.44	565.6 156.35	+3.69 kB +906 B
WebGPU Nodes	560.51 155.2	564.21 156.1	+3.69 kB +905 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	469.77 113.61	469.77 113.61	+0 B +0 B
WebGPU	636.77 172.32	636.95 172.36	+178 B +45 B
WebGPU Nodes	591.42 161.55	591.6 161.59	+178 B +34 B

[bhouston]

@sunag, do you know why the mx_ nodes are defined in two places and what makes one choose one location over the other:

three.js/src/nodes/materialx/MaterialXNodes.js

Line 13 in 0b7bcc0

export const mx_aastep = ( threshold, value ) => {

three.js/examples/jsm/loaders/MaterialXLoader.js

Line 38 in 0b7bcc0

const mx_add = ( in1, in2 = float( 0 ) ) => add( in1, in2 );

I put all my new nodes in the MaterialXLoader, but I just tried to minimize changes to the code of ThreeJS.

But I think it may be best to have a separate MaterialXNodes that is not in the core ThreeJS package and can be referenced by the MaterialXLoader as well as other files, like the upcoming GlTF support for MaterialX node graphs.

[sunag]

@sunag, do you know why the mx_ nodes are defined in two places and what makes one choose one location over the other:

These Nodes were created specifically for MaterialXLoader because TSL has its own equivalents, like add instead of mx_add. But we can move them all to MaterialXNodes as well.

Awesome work 🚀

[bhouston]

@sunag it turns out a bunch of examples use the mx_ functions, particularly the noise functions, from the TSL nodes:

• webgpu_lights_projector
• webgpu_tsl_procedural_terrain
• webgpu_tsl_raging_sea

Hmm... not sure how to handle this.

[sunag]

But I think it may be best to have a separate MaterialXNodes that is not in the core ThreeJS package and can be referenced by the MaterialXLoader as well as other files, like the upcoming GlTF support for MaterialX node graphs.

Sorry @bhouston , I didn't pay attention to that. Wouldn't it be better to just move the new nodes to MaterialXNodes and keep them in the core? It supports tree-shaking and many users already use it this way.

[bhouston]

@sunag I've made the requested change and centralized all mx_* nodes into MaterialXNodes within the src/nodes/MaterialX directory.

[bhouston]

@sunag - I got a nasty merge conflict and then I messed up git and somehow lost your branch and got a nasty conflict - so I undid all that. Can you re-push your changes with a new name as I've lost them? I've kept working on this branch without your changes.

I just added proper "time" support and a time example. :)

[DennisSmolek]

@bhouston How are you getting your nodes out of Blender? I

[jo-chemla]

@bhouston mentioned this addon he's been working on bhouston/materialx_addon

in the glTF-Blender-IO discussion here KhronosGroup/glTF-Blender-IO#2582 (comment)