I have this formula to get the isometric X and Y given 2D coordinates for an isometric video game
//Isometric X Position (((u_blockRotation*(a_position) + u_blockRotation*(a_position))*(27.0))-u_camera)*u_resolution*u_zoom/u_screenSize, //Isometric Y Position (((u_blockRotation*(a_position) + u_blockRotation*(a_position))*(13.0))-u_camera)*u_resolution*u_zoom/u_screenSize,
It uses the current resolution, zoom factor, and screen size plus the rotation variables of the map to correctly place them on the screen. I need to solve the system of equation for a_position in order to get a formula to turn screen space coordinates into grid coordinates. When I try to do this I end up with something very nasty, and online system of equation solves are not able to resolve it.