Applying two different fragment shaders to two different materials (of the same type) using onBeforeCompile? - three.js

Question

I've imported a GLTF file with two different meshes. My goal is to give each mesh a material with a unique custom fragment shader using onBeforeCompile. Each mesh has the same type of material (MeshNormalMaterial).
When I try to apply one fragment shader to one material and the other fragment shader to the other material, both materials wind up with the same fragment shader. The fragment shader each material has depends on which material I setup first.
Here's a few pictures showing what I'm talking about:
Below is all the relevant code.
Main code: This is the general structure of my code. I've enclosed the important part between "PRIMARY AREA OF INTEREST" comments. For simplicity, I've replaced my shader code with "..." or a comment describing what it does. They do work as shown in the pictures above.
// Three.JS Canvas
const threeDisplay = document.getElementById("threeDisplay");
// Globals
var displayDimensions = getElemDimensions(threeDisplay); // Uniform
var currentTime = 0; // Uniform
var helix = null; // Mesh
var innerHelix = null; // Mesh
var horseshoe = null; // Mesh
// Set the scene and camera up
const scene = new THREE.Scene();
const camera = initCamera();
// Setup a directional light
const light = new THREE.DirectionalLight( 0xffffff, 1.0 );
light.position.set(-0.2, 1, -0.6);
scene.add(light);
// Setup WebGL renderer
const renderer = initRenderer();
threeDisplay.appendChild( renderer.domElement );
// Load the gltf model
new GLTFLoader().load( "./spiral_pillar_hq_horseshoe.glb", function (object) {
const helixFragmentShaderReplacements = [
{
from: ' ... ',
to: ' // rainbow '
}
];
const horseshoeFragmentShaderReplacements = [
{
from: ' ... ',
to: ' // white '
}
];
//////////////////////////////////////
// PRIMARY AREA OF INTEREST - START //
//////////////////////////////////////
// Turn the horseshoe into a shader.
horseshoe = object.scene.children[1];
var horseshoeGeometry = horseshoe.geometry;
var horseshoeMaterial = shaderMeshMaterial(new THREE.MeshNormalMaterial(), horseshoeGeometry, horseshoeFragmentShaderReplacements);
var horseshoeMesh = new THREE.Mesh(horseshoeGeometry, horseshoeMaterial);
horseshoe = horseshoeMesh;
horseshoe.rotation.z = deg2rad(180); // Re-orient the horseshoe to the correct position and rotation.
horseshoe.position.y = 13;
scene.add(horseshoe);
// Turn the inner helix into a colorful, wiggly shader.
helix = object.scene.children[0];
var helixGeometry = helix.geometry;
var helixMaterial = shaderMeshMaterial(new THREE.MeshNormalMaterial(), helixGeometry, helixFragmentShaderReplacements);
var helixMesh = new THREE.Mesh(helixGeometry, helixMaterial);
helix = helixMesh;
scene.add(innerHelix);
animate();
////////////////////////////////////
// PRIMARY AREA OF INTEREST - END //
////////////////////////////////////
}, undefined, function (error) {
console.error(error);
});
Below are functions which are relevant.
shaderMeshMaterial: Constructs a new material based on the supplied materialType that supports editing the default shader. If it's not initProcessing, then the problem may stem from this function.
// Globals used: displayDimensions
function shaderMeshMaterial(materialType, geometry, fragmentShaderReplacements) {
var material = materialType;
material.onBeforeCompile = function ( shader ) {
// Uniforms
shader.uniforms.time = { value: 0 };
shader.uniforms.resolution = { value: new THREE.Vector2(displayDimensions.width, displayDimensions.height) };
shader.uniforms.bboxMin = { value: geometry.boundingBox.min };
shader.uniforms.bboxMax = { value: geometry.boundingBox.max };
fragmentShaderReplacements.forEach((rep) => {
shader.fragmentShader = shader.fragmentShader.replace(rep.from, rep.to);
});
console.log(shader);
material.userData.shader = shader;
}
return material;
}
initRenderer: Sets up the renderer. Just showing you guys the renderer setup I have in case that's important.
// Globals used: displayDimensions
function initRenderer() {
var renderer = new THREE.WebGLRenderer({
alpha: true,
antialias: true,
precision: "mediump"
});
renderer.setClearColor( 0x000000, 0);
renderer.setPixelRatio( window.devicePixelRatio );
renderer.setSize( displayDimensions.width, displayDimensions.height );
renderer.shadowMap.enabled = true;
renderer.outputEncoding = THREE.sRGBEncoding;
renderer.toneMapping = THREE.ACESFilmicToneMapping;
renderer.toneMappingExposure = 1.25;
return renderer;
}
animate: Handles the animation frames.
// Globals used: renderer, currentTime, postprocessing
function animate (timestamp = 0) {
requestAnimationFrame(animate);
resizeRendererToDisplaySize(renderer);
currentTime = timestamp/1000; // Current time in seconds.
scene.traverse( function ( child ) {
if ( child.isMesh ) {
const shader = child.material.userData.shader;
if ( shader ) {
shader.uniforms.time.value = currentTime;
}
}
} );
renderer.render( scene, camera );
postprocessing.composer.render( 0.1 );
};
One last thing to note is that when I inspected the console log of shader from the shaderMeshMaterial function, I can see that the fragment shaders are indeed different as they should be for each material. Also not sure why there are 4 console logs when there should only be 2.
Sorry for all the code, but I did condense it to where all irrelevant code was stripped out. I'm fairly new to Three.JS, so any possible explanations as to why this is happening are much appreciated!
EDIT: Removed vertex shader parameter from shaderMeshMaterial function to keep this question focused on just the fragment shaders. Though this problem does apply to both the vertex and fragment shaders, I figure if you fix one then you'll fix the other.
EDIT 2: Added language identifiers to code snippets. Also I removed the postprocessing function and the problem still persists, so I know the problem isn't caused by that. I've updated the code above to reflect this change. As a happy side effect of removing the postprocessing function, the console.log of the shader variable from shaderMeshMaterial new appears twice in the log (as it should).
EDIT 3: (Implementing WestLangley's suggestion) I tweaked the shaderMeshMaterial function by adding the customProgramCacheKey function. I had to condense the four parameters of shaderMeshMaterial into one for the sake of the customProgramCacheKey function. I believe I implemented the function correctly, but I'm still getting the same result as before where both materials display the same fragment shader.
New "PRIMARY AREA OF INTEREST" code:
horseshoe = object.scene.children[1];
var horseshoeGeometry = horseshoe.geometry;
var meshData = {
materialType: new THREE.MeshNormalMaterial(),
geometry: horseshoeGeometry,
fragmentShaderReplacements: horseshoeFragmentShaderReplacements
}
var horseshoeMaterial = shaderMeshMaterial(meshData);
var horseshoeMesh = new THREE.Mesh(horseshoeGeometry, horseshoeMaterial);
horseshoe = horseshoeMesh;
horseshoe.rotation.z = deg2rad(180); // Re-orient the horseshoe to the correct position and rotation.
horseshoe.position.y = 13;
scene.add(horseshoe);
// Turn the inner helix into a colorful, wiggly shader.
helix = object.scene.children[0];
var helixGeometry = helix.geometry;
var meshData2 = {
materialType: new THREE.MeshNormalMaterial(),
geometry: helixGeometry,
fragmentShaderReplacements: helixFragmentShaderReplacements
}
var helixMaterial = shaderMeshMaterial(meshData2);
var helixMesh = new THREE.Mesh(helixGeometry, helixMaterial);
helix = helixMesh;
scene.add(innerHelix);
animate();
New shaderMeshMaterial code:
// Globals used: displayDimensions
function shaderMeshMaterial(meshData) {
var material = meshData.materialType;
material.onBeforeCompile = function ( shader ) {
// Uniforms
shader.uniforms.time = { value: 0 };
shader.uniforms.resolution = { value: new THREE.Vector2(displayDimensions.width, displayDimensions.height) };
shader.uniforms.bboxMin = { value: meshData.geometry.boundingBox.min };
shader.uniforms.bboxMax = { value: meshData.geometry.boundingBox.max };
meshData.fragmentShaderReplacements.forEach((rep) => {
shader.fragmentShader = shader.fragmentShader.replace(rep.from, rep.to);
});
material.customProgramCacheKey = function () {
return meshData;
};
console.log(shader);
material.userData.shader = shader;
}
return material;
}

Answer 1

WestLangley suggestion worked for me!
material.onBeforeCompile = ...
// Make sure WebGLRenderer doesnt reuse a single program
material.customProgramCacheKey = function () {
return UNIQUE_PER_MATERIAL_ID;
};
I believe your mistake is returning meshData from customProgramCacheKey.
I think customProgramCacheKey need concrete identifier like a number or string.
It would be nice to understand what exactly happening and why do we need to specify customProgramCacheKey.
EDIT: I discover that default value for customProgramCacheKey calculated as follow in Threejs source.
customProgramCacheKey() {
return this.onBeforeCompile.toString();
}
Perhaps this is explains this default caching behavior because calling toString on function returns that function body literally as string.
For example consider function const myFunc = () => { return 1 }. Calling myFunc.toString() returns "() => { return 1 }"
So if your calling onBeforeCompile in a for loop you function body as string never change.