vsub method
Vector subtraction @param target Optional target to save in.
Implementation
Vec3 vsub(Vec3 vector, [Vec3? target]){
if (target != null) {
target.x = x-vector.x;
target.y = y-vector.y;
target.z = z-vector.z;
return target;
} else {
return Vec3(x - vector.x, y - vector.y, z - vector.z);
}
}