Apply 2D orientation to particles - three.js

Question

First time using three.js and I'm doing a very simple particle animation in which I'm mapping 4 different textures. So far everything is working as desired except that I can't figure out how to rotate particles so that they're rendered with a random orientation (upside down, sideways, etc.) Any help would be appreciated!

You can see my progress so far here: http://development.shapes.divshot.io/particles.html

And here is the relevant code:

            sprite1 = THREE.ImageUtils.loadTexture( "sprite1.png" );
            sprite2 = THREE.ImageUtils.loadTexture( "sprite2.png" );
            sprite3 = THREE.ImageUtils.loadTexture( "sprite3.png" );
            sprite4 = THREE.ImageUtils.loadTexture( "sprite4.png" );

            parameters = [ sprite1, sprite2, sprite3, sprite4];

            for ( i = 0; i < parameters.length; i ++ ) {

                sprite = parameters[i];

                materials[i] = new THREE.PointCloudMaterial( { size: 45, map: sprite, depthTest: false, transparent : true} );


                particles = new THREE.PointCloud( geometry, materials[i] );

                particles.rotation.x = Math.random() * 60;
                particles.rotation.y = Math.random() * 60;
                particles.rotation.z = Math.random() * 60;

                scene.add( particles );

            }

Using three.js r71

Answer 1

AFAIK the three.js PointCloud/PointCloudMaterial particle system uses gl.POINTS to draw the points. Which means it has several limitations.

1. You can't rotate the points.

   You can rotate the UV coordinates in your fragment shader if you write a custom shader but that won't help if your image fills the point because rotating a square texture inside a square will clip the corners as it rotates.

2. You can't make points larger than the max point side of the GPU/Driver you're on.

   WebGL only requires the max size = 1.0 which means there are GPUs/Drivers that only support 1 pixel large points.

   Checking webglstats.com it looks like the number of GPUs/Drivers that only support 1 pixel large points has gotten smaller. There's still about 5% of machines that only support points 63 pixels and smaller which should only be an issue if you're flying through a point field.

3. You can only have square points.

   You can't have rectangular point if you wanted something long and thin like a spark for example.

One solution is to make your own particle system that uses quads and can rotate their vertices as well as scale them in multiple directions. This example runs entirely on the GPU. Unfortunately it is not three.js based.