rendering solar tower plant (was: Questions about spotlight and specularity)

Hi Joe,

The "mirror" type is working, which is excellent and means you have things oriented properly.

I wouldn't expect either of the other types to work, because as I mentioned, a limitation of backwards ray-tracers is that they need to know where to look for light sources. The "mirror" type creates virtual light sources that allow the calculation to work, but the other two types do not. You might get them to work with the photon map, however.

You should know that setting the transmission of a dielectric does not give you a 100% reflecting material. At most, you'll get about 5% reflectance, but again, the calculation still needs to know where to look, and it does not.


P.S. It's best to keep the subject the same, so the thread holds together on the list archives.


From: Joe <[email protected]>
Date: August 2, 2017 9:24:57 AM PDT

Hello Greg,

thanks for you help. I made some progress on this and have new questions :slight_smile:

The image linked below shows three scenarios I tried.

The left image shows heliostats reflecting the sun [source, at 0, 0, 1, ring with 0.5°] onto the receiver. This works fine so far.

But I also tried other materials that I would have expected to work.

The middle image uses a white glossy plastic with specularity 1.0 and roughness 0.0 . I would have expected to see the reflection on the receiver, too.

Same for the right picture, here I used a non-transmitting dielectric.
I would have expected that the complete radiation is reflected.

Do you have an idea what might causethis behaviour or what I might have missed?

Kind regards,