Yesterday, I released a project for calculating whether a 2D point lay inside a 2D triangle: https://scratch.mit.edu/projects/117040925 This project is its big brother: - The triangle is 3D (each vertex has an x, y and z co-ordinate) - We are detecting whether a 3D ray intersects with it - If it does intersect, then we find the distance the ray travels Based on the algorithm detailed here: http://cg-dev.ltas.ulg.ac.be/inf/Fast%20MinimumStorage%20RayTriangle%20Intersection.pdf