for my map editor for an RTS game I have a heightmap terrain grid i need to find the grid point that is closest to the mouse point. i''m using an orthographic view that is rotated on a slight angle. when viewing the map straight down the screen coords are the same as the world coordinates. but when its on an angle, things change a bit, so i need a way to determine which point is directly below the mouse point whatever angle its on. i''ve had a look at the gluUnproject functions but i couldnt figure out how to get these to work.