My first ever attempt at ray-tracing. I gave a try to OCC's super new CAD Rays.
I mocked up a scene, with a lens I thought I designed to focus perfectly...

- lens scene cad.png (30.69 KiB) Viewed 12044 times
And I tried to render it, in hope to see the image of objects in front of the lens. But all I got was lots of stray light, and no actual image. Then I removed the objects, and placed a light source. At first, I got something strange and very slowly, but I realized I forgot to switch off the sun

, and after doing that...

- lens scene.png (642.63 KiB) Viewed 12044 times
To my disappointment, the result is still very noisy after a few minutes of waiting.

But it definitely shows something useful. It demonstrates that my lens is very far from perfect. All that halo around the image...
So I went back to FreeCAD, and checked the design. Sure enough...

- lens scene lens design.png (414.16 KiB) Viewed 12044 times
It's definitely cool to see stuff like this! But I'm not happy with the UI of CADRays. It's strange. Moving around is hard. It often becomes very laggy, so I have to switch over to opengl rendering. It doesn't like touchscreen input, and even with pen, I often find out CADRays decided I want to drag the wrong numberbox, or reset my hue value of color, or not accept light source power below 1.0...
I want gesture navigation style from FreeCAD to be in there! I still have not figured out how to pan! (apart from AWSD)