transformDirection method
Implementation
Vector3 transformDirection(Matrix4 m) {
// input: three.Matrix4 affine matrix
// vector interpreted as a direction
var x = this.x, y = this.y, z = this.z;
var e = m.elements;
this.x = e[0] * x + e[4] * y + e[8] * z;
this.y = e[1] * x + e[5] * y + e[9] * z;
this.z = e[2] * x + e[6] * y + e[10] * z;
return normalize();
}