Material basics for Rhino 6 (11 min)
Viewport “Render” mode
The Render Mode is very well suited for fast visualizations in the design process.
Rendering in “Raytraced” mode
For raytraced render mode: you need a fast graphic card (GPU), ideally Nvidia graphic card with a lot of CUDA.
If you have performance issues try a smaller viewport resolution/size.
Render image-files by “Viewport/capture/capture to file”.
For more issues with raytrace render: link