vectorCrossProd = function( vec1, vec2 ) {
            return {
                x: vec1.y * vec2.z - vec1.z * vec2.y,
                y: vec1.z * vec2.x - vec1.x * vec2.z,
                z: vec1.x * vec2.y - vec1.y * vec2.x
            };
        }
Cross product of two vectors.

https://en.wikipedia.org/wiki/Cross_product