from-3d-to-2d

Take a transformation matrix like you're used to constructing with WebGL, and project arbitrary 3D points onto your 2D screen.

You can use this to take a point in your WebGL scene and get its onscreen position on the canvas, e.g. to add DOM element overlays, or bootstrapping your own canvas/SVG.

Usage

transform(out, position, matrix)

Given a 3-element array position and a 16-element array matrix, update the out array to contain your new 2D points – each of them ranging from 0 to

1. For example:

var mat4       = require('gl-matrix').mat4
var camera     = require('orbit-camera')()
var transform  = require('from-3d-to-2d')

var projection = new Float32Array(16)
var view       = new Float32Array(16)
var pvMatrix   = new Float32Array(16)
var point      = new Float32Array(2)

function render() {
  // get your camera/view matrix from something like orbit-camera
  camera.view(view)

  // perspective projection
  mat4.perspective(projection
    , Math.PI / 4                  // field of view
    , canvas.width / canvas.height // aspect ratio
    , 0.00001
    , 10000
  )

  // Combine your matrix transformations into
  // a single transform by multiplying them together
  mat4.mul(pvMatrix, projection, view)

  // get your 2d point from your 3d point:
  transform(point, [0, 0, 0], pvMatrix)
  var x = point[0]
  var y = point[1]
}

See Also

• svg-simplicial-complex
• orbit-camera
• gl-matrix
• perspex

License

MIT. See LICENSE.md for details.