AutoCADFast shaded mode is not available. The Model Viewer will close; check your graphics settings using the GRAPHICSCONFIG command. The primary cause is that your graphics card (or its driver) does not support the required fast (GPU hardware-accelerated) shading mode. If the problem occurs on a laptop or a computer with two graphics cards, first verify that Civil/ AutoCAD is actually running on your fast, accelerated graphics card. Or change the graphics mode - to DirectX first - using the GFXDX12 variable, or by selecting a setting in the GRAPHICSCONFIG command.