1) use texture coordinates (vertex UVW), edit them manually in code or use a 3D modeller/editor that can output b3d format.
2) in minib3d there is a GUI canvas example. Or clear the screen , render the 3D scene and then after draw 2D over/around it if you don't use maxgui.
2) in minib3d there is a GUI canvas example. Or clear the screen , render the 3D scene and then after draw 2D over/around it if you don't use maxgui.