cross function
Computes the cross product of two vec2's Note that the cross product must by definition produce a 3D vector
@param {vec3} out the receiving vector @param {ReadonlyVec2} a the first operand @param {ReadonlyVec2} b the second operand @returns {vec3} out
Implementation
List<double> cross(out, a, b) {
var z = a[0] * b[1] - a[1] * b[0];
out[0] = out[1] = 0;
out[2] = z;
return out;
}