Learn about CPU rasterization when raytracing in VRED.
Video captions: Open the Render Settings, via the Quick Access Bar. Select under Raytracing Quality, CPU Raytracing for both Interactive and Still Frame. Activate the Raytracing mode. The CPU rasterization mode is in principle, identical to the OpenGL mode, just that the computational processes are handled by the CPU. Using this mode is reasonable, should the performance of your graphics card not be sufficient or if large sets of data are used.