Scenes Shipping with LuxCoreRender
Here some images from LuxCoreRender's example scenes:
The laser rays hit a lens that diffuses rays only vertically (due to its shape), then these rays enter the prism and travel to the location of the empty. By upscaling lens1 the rainbow appears shorter vertically, or longer if downscaled. Luxcore with bidir+metropolis enabled can handle very complex lighting correctly if enough time is given.