Crookes Radiometer



Aha! That brings back memories! I was fascinated with these when I saw them at a local science center - so much so that I bought one when I was 10 years old!


It looks so real. Great job!!!


Great job there

I’ve just looked at this again asked myself whether a shadow like that would cast from a transparent material or would mainly the “vanes” cast the shadow?
Maybe SketchUp hasn’t took into account the transparency applied and only sees the outer sphere as a light “blocker”?

I don’t think I’ve noticed this before, tell me if I’m wrong?


It’s rendered with KerkyThea outside of SketchUp, so it’s not a SketchUp thing.

I think it depends on the material and the shape … here’s a thread where I created some lenses using various smoothing versus no smoothing:

Generally (Kerky)Thea does a very good job tracing the actual paths the light should follow.


KerkyThea offers 25 different rendering algorithms that take a few seconds to a few hours, depending on the algorithm and the geometry. Here’s one using a fast Ray Tracing render:

Using a bi-directional ray tracing algorithm produces this:

Note that I made some minor alterations to the vane support.


Yes, the second one is what my mind was telling me how a shadow would cast. That looks really good.

Nice job.



That’s brilliant, those shadows really do look good.


I want to thank you for pointing out the lack of the shadows. I was already about a third of the way through animating the images with the previous algorithm when you mentioned it. I went back and redid them again with the better algorithm :slight_smile:


Cheers, it wasn’t until someone commented and I looked at it again, that I spotted something looked amiss. I didn’t mean anything bad by what I said nor do I understand the rendering process.
I am glad it was useful to you though, it’s a real work of art now!