splineForward = function(segments, matrix) {
      var f = 1.0 / segments;
      var ff = f * f;
      var fff = ff * f;

      matrix.set(0, 0, 0, 1, fff, ff, f, 0, 6 * fff, 2 * ff, 0, 0, 6 * fff, 0, 0, 0);
    }
The function splineForward() setup forward-differencing matrix to be used for speedy
curve rendering. It's based on using a specific number
of curve segments and just doing incremental adds for each
vertex of the segment, rather than running the mathematically
expensive cubic equation. This function is used by both curveDetail and bezierDetail.

@param {int} segments      number of curve segments to use when drawing
@param {PMatrix3D} matrix  target object for the new matrix