mat4-interpolator

Builds an interpolator that acts on two 4x4 matrices, using algorithms from W3C Spec to produce consistent results with CSS animations. Translation, scale, skew and perspective are interpolated linearly, and rotation is interpolated with spherical interpolation.

var start = mat4.create()
var end = mat4.fromRotationTranslation([], [0,1,0,0], [20, 50, -10])
var out = mat4.create()

//create the interpolator
var lerp = require('mat4-interpolator')(start, end)

if (!lerp) { 
    //returns false is the matrices cannot be inverted
    //in this case you need to fall back to your own animation method
    lerp = discreteAnimator
}

//.. in your render loop
function render() {
    //interpolate based on alpha, storing results in 'out' matrix
    lerp(out, alpha)
}

Note: mat4-interpolate is recommended for most use cases, but this module may be useful to avoid decomposing static matrices every frame.

You can run the demo on RequireBin:

http://requirebin.com/?gist=1347c3e7fd430a191545

Usage

lerp = createInterpolator(start, end)

Creates an interpolator function that acts on the target start and end matrices. This will decompose the two matrices into components. If either matrix is non-invertible (i.e. scale or perspective W of zero), this method returns false. W3C suggests falling back to discrete animations in this case.

lerp(out, alpha)

The returned function accepts an out matrix for storing the interpolated results, and an alpha for how much to interpolate.

Returns the out matrix.

License

MIT, see LICENSE.md for details.