prism or coloured dispersion caustics

[south]

Hi guys, having issues trying to get the traditional chromatic spread from a prism. I've read in some places that this isn't possible due to the nature of the octane but Fooze managed it here: viewtopic.php?f=25&t=40134 and some other users in the standalone. Is this possible to recreate in C4D? I've tried cranking my PMC to crazy numbers to no avail (I'm on twin 1080's). Tried using a low IOR, a high IOR, dispersion etc etc but I feel like I'm prodding in the dark with hopes of a happy accident.

Scene file attached, I'm getting some VERY subtle colour on some of the caustics as per the image below. Any advice would be greatly appreciated!

[atome451]

Hi,
If you use "Fake shadows" on specular material of the prism, it will not work at all.
There is a lot of other possible optimizations on your file but this is the main one to have a prism effect.

[bepeg4d]

Hi south,
please, have a look at this other discussion on the same argument:
viewtopic.php?f=9&t=63783&p=325197&hili ... cs#p325197
ciao beppe

[south]

Thanks atome, I'll give that a go.

Beppe... I did come across that thread but my light is tiny and even after 10-15 minutes of ludicrous high settings I still couldn't get anything. I also tried scaling to 1/10 and 10/1. Is there any chance you could post your example please?

[bepeg4d]

Hi south,
unfortunately, I was not able to find my old scene, so I have downloaded your scene, and made few changes:

As atom said, firstly you need to untick the fake shadow option, then correct the index to 1.55, add an environment black object to remove the indirect illumination of the sky, and increase a lot the exposure to clearly see the effect.
Note that the kernel settings are the same.

prism_0001.c4d.zip

(86.28 KiB) Downloaded 647 times

ciao beppe

[south]

You're an absolute gent Beppe, thank you so much!