The program has the error before you click the run button so that means the error will be in code that happens before the run button, most likely the world class. If you make this project open-source I could try to fix it.

The first thing to consider is how to plot in 3D, I simply plotted ( x , y + z ). This may cause a little problem in looks since the cube in the scenario is a little taller than it is wide, but it still works.

My project does not seem to work on the website, it was working fine in the editor. This is somehow happening in many of my projects. Sorry for the inconvenience. :(

I came up with the engine myself, it uses a simple algorithm to find the x,y,z plot after rotating each point, in this case, eight points for a cube. If you want to know them, I'd be happy to comment them here.