Before starting to render (draw) a 3D frame, the window surface is filled out by the specified color scene background color or by a texture. The color can be specified like other colors of the Peter system either by the color constant element or by the compound color components to color element. If the entire surface of a window is covered with objects (e.g. the walls of a room), then the filling out of the scene background can be switched off by setting the numeric value to -1 instead of setting a color. Thus the rendering speed can be increased slightly. The state of the switched off filling out of the scene background can also serve to reach special effects (shadows behind moving objects, multiple rendering using different object coordinates). By setting the scene background color the scene background texture is switched off.