Three.js - Using multiple textures in a single PointCloud

I'm trying to use multiple textures in a single PointCloud using a ShaderMaterial. I'm passing a texture array to the shader along with texture index attributes and selecting the appropriate texture to use in the fragment shader.

Relevant Setup Code:

var particleCount = 100;

var uniforms = {
    textures: {
        type: 'tv',
        value: this.getTextures()
    }
};

var attributes = {
    texIndex: {
        type: 'f',
        value: []
    },
    color: {
        type: 'c',
        value: []
    },
};

var material = new THREE.ShaderMaterial({
    uniforms: uniforms,
    attributes: attributes,
    vertexShader: document.getElementById('vertexShader').textContent,
    fragmentShader: document.getElementById('fragmentShader').textContent,
    transparent: true
});

var geometry = new THREE.Geometry();

for (var i = 0; i < particleCount; i++) {
    geometry.vertices.push(new THREE.Vector3(
    (Math.random() - 0.5) * 50, (Math.random() - 0.5) * 50, (Math.random() - 0.5) * 50));
    attributes.texIndex.value.push(Math.random() * 3 | 0);
    attributes.color.value.push(new THREE.Color(0xffffff));
}

var particles = new THREE.PointCloud(geometry, material);
particles.sortParticles = true;
this.container.add(particles);

Vertex Shader:

attribute vec3 color;
attribute float texIndex;

varying vec3 vColor;
varying float vTexIndex;

void main() {
    vec4 mvPosition = modelViewMatrix * vec4(position, 1.0);

    vColor = color;
    vTexIndex = texIndex;

    gl_PointSize = 50.0;
    gl_Position = projectionMatrix * mvPosition;
}

Fragment Shader:

uniform sampler2D textures[3];

varying vec3 vColor;
varying float vTexIndex;

void main() {
    vec4 startColor = vec4(vColor, 1.0);
    vec4 finalColor;

    if (vTexIndex == 0.0) {
        finalColor = texture2D(textures[0], gl_PointCoord);
    } else if (vTexIndex == 1.0) {
        finalColor = texture2D(textures[1], gl_PointCoord);
    } else if (vTexIndex == 2.0) {
        finalColor = texture2D(textures[2], gl_PointCoord);
    }

    gl_FragColor = startColor * finalColor;
}

The problem is some points (ones using a texture index higher than 0) are flickering for reasons and can't figure out. Other attempts have also seemed to flicker between textures rather than opacity.

An example of this can be seen at http://jsfiddle.net/6qrubbk6/4/.

I've given up on this over multiple projects but I'd love to find a solution once and for all. Any help is greatly appreciated.

Edit: Checking if vTexIndex is < n, instead of == n solves the issue.

if (vTexIndex < 0.5) {
    finalColor = texture2D(textures[0], gl_PointCoord);
} else if (vTexIndex < 1.5) {
    finalColor = texture2D(textures[1], gl_PointCoord);
} else if (vTexIndex < 2.5) {
    finalColor = texture2D(textures[2], gl_PointCoord);
}

As seen here: http://jsfiddle.net/6qrubbk6/5/

Answers:

Answer

Also you can cast vTexIndex to int.

int textureIndex = int(vTexIndex + 0.5);

if (textureIndex == 0) {
    finalColor = texture2D(textures[0], gl_PointCoord);
} else if (textureIndex == 1) {
    finalColor = texture2D(textures[1], gl_PointCoord);
} else if (textureIndex == 2) {
    finalColor = texture2D(textures[2], gl_PointCoord);
}
Answer

Thanks for replying to your own question. You helped me get started on a similar feature I was working.

I thought this might be helpful to someone else so I'm replying here.

I've created a fiddle that does what you're doing, but dynamically. You can add as many textures to the textures array and they will be dynamically added to the nodes. This was tricky to do in glsl, and required some hacky javascript templating.

To do this, I just created 2 methods that return the vertex and fragment shader to the shader material:

Fragment Shader Method:

World.prototype.getFragmentShader = function(numTextures){
var fragShader =  `uniform sampler2D textures[${numTextures}];

varying vec3 vColor;
varying float vTexIndex;

void main() {
    vec4 startColor = vec4(vColor, 1.0);
    vec4 finalColor;

    `;
  for(var i = 0; i < numTextures; i++){
    if(i == 0){ 
      fragShader += `if (vTexIndex < ${i}.5) {
        finalColor = texture2D(textures[${i}], gl_PointCoord);
        }
      `
    }
    else{
      fragShader += `else if (vTexIndex < ${i}.5) {
        finalColor = texture2D(textures[${i}], gl_PointCoord);
        }
      `
    }
  }
fragShader += `gl_FragColor = startColor * finalColor;
}`;

console.log('frag shader: ', fragShader)
return fragShader;
}

Vertex Shader:

World.prototype.getVertexShader = function(){

let vertexShader = `attribute vec3 color;
attribute float texIndex;

varying vec3 vColor;
varying float vTexIndex;

void main() {
    vec4 mvPosition = modelViewMatrix * vec4(position, 1.0);

    vColor = color;
    vTexIndex = texIndex;

    gl_PointSize = 50.0;
    gl_Position = projectionMatrix * mvPosition;
}`;

return vertexShader;
}

You can see a live demo here: http://jsfiddle.net/jigglebilly/drmvz5co/

Answer

The new version of Three.js doesn't support attributes in ShaderMaterial. We'll have to delete attributes: attributes in new THREE.ShaderMaterial and use geometry.addAttribute instead. Here's the code to define texIndex:

var vIndex = new Float32Array( vertices.length );
for ( var i = 0, l = vertices.length; i < l; i ++ ) {
        vIndex[i] = Math.random()*getTextures().length;
}
geometry.addAttribute( 'texIndex', new THREE.BufferAttribute( vIndex, 1 ) );

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