This topic is a bit similar to an old topic of mine "Real 3D Mask", only this time I know a little more what I need and how I need it.   I created a box mesh.   I'd like to create a shader in which I can specify the y of 2 lines: -top line - nothing above it is drawn -bottom line - nothing below it is drawn   The areas above the top line or below the bottom line should be "cut" in a 3d way, a 2d mask or anything of the sort will have a bad looking result.