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gl-particles

gl-particles

experimental

Convenience module for FBO-driven particle simulations.

view demo

Usage

NPM

See demo.js for a full example.

particles = Particles(gl, options)

Creates a new particle simulation given a WebGLContext gl and set of options:

  • logic: the logic shader for simulating the particles, as a string. Required.
  • vert: the vertex shader responsible for determining the rendered particles' position and size. Required.
  • frag: the fragment shader responsible for determining the color/texture of each particle. Required.
  • shape: a [width, height] array for the dimensions of the particle texture. This determines the total amount of particles, which should be width * height. Defaults to [64, 64].

Your logic shader will automatically be assigned the following uniforms:

  • sampler2D data: the particle data texture.
  • vec2 resolution: the width/height of the data texture.

And your fragment/vertex shaders will be assigned the following:

  • sampler2D data: the particle data texture.

particles.populate((u, v, vec4) =>)

Populates the data for each particle in your FBO textures individually.

  • u is the horizontal index of the particle in pixels.
  • v is the vertical index of the particle in pixels.
  • vec4 is a 4-element array which you should modify in-place to update the current particle's values.

For example, if you have 2D positions for your particles you would set them randomly like so:

particles.populate(function(u, v, vec4) {
  vec4[0] = Math.random() * 2 - 1
  vec4[1] = Math.random() * 2 - 1
})

particles.step((uniforms) =>)

Runs one step of the logic shader – should generally be done once per frame.

You may optionally pass in a function to update the shader's uniforms, e.g.:

var start = Date.now()
 
particles.step(function(uniforms) {
  uniforms.time = (Date.now() - start) / 1000
})

Note that this will modify your WebGL state. Specifically, it will reset your current framebuffer, viewport and shader.

particles.draw((uniforms) =>)

Draws your particles to the screen using the vert and frag shaders.

As with particles.step, you may pass in an optional function for updating the shader's uniforms.

particles.setLogicShader(logicShaderSource)

Change the logic shader to logicShaderSource.

Contributing

See stackgl/contributing for details.

License

MIT. See LICENSE.md for details.