vray 2.0 dispersion and volume caustics

[Mnietek2707]

This is my try with dispersion and volume caustics.



I have questions:

1. Caustics are almost invisibile inside prism (except caustics from internal reflections).
Is this normal? Is it because there is no fog inside the prism?
When I render similar scene in v-ray 1.5 there was no such difference in caustics brightnes. This is example:




2. Prism is simple extruded N-gon. Caustics are not visible until I add subdivide modifier to this object.
Maybe this is a bug?


______
sorry for my English

[simmsimaging]

I seem to have a lot of issues with caustics and dispersion as well. Not sure why, but indirectly visible caustics don't always seem to show up. Very interested in this issue too.

b

[Danculo]

Mnietek Hi,
would you send me your scene of the first picture? (just send it to vray@chaosgroup.com)
I'm trying to reproduce it in order to see what exactly is happening there, but i don't get pictures like yours.

Dani

[Mnietek2707]

I sent an e-mail...

[vlado]

So there are several problems in the scene:

1) The light is perfectly horizontal - this seems to cause issues when not using gizmos and just the height; will fix it, but in the meantime, just tilt the light slightly in the Z direction;

2) The "atmospheric shadows" option for the light was disabled, which caused discrepancy between the caustics and the normal lighting;

3) The "optimize atmoshperic effects" option in the global V-Ray settings is off, which causes further issues with the photon map. When using caustics with VRayEnvironmentFog, it is always recommended to turn this option ON - I will put a warning in the V-Ray log about this.

Best regards,
Vlado

[Jiri.Matys]

Can You post this scene to everyone?

[Mnietek2707]

here is original file - without modifications suggested by Vlado

max 2011
pryzmat02_mail.zip

[Jiri.Matys]

Thanks a lot.

[Jiri.Matys]

With changes from Vlado it looks great, without any problem I think.

[Mnietek2707]

Thanks for suggestions Vlado

These are my attempts
When optimize atmoshperic is ON caustisc from internal reflections are gone. Is this normal?

optimize atmoshperic ON



optimize atmoshperic OFF



By the way: if I want to change fog density inside prizm. Is it possible?

_______
sorry for my English

[vlado]

Thanks for suggestions Vlado

These are my attempts
When optimize atmoshperic is ON caustisc from internal reflections are gone. Is this normal?

optimize atmoshperic ON
[ATTACH=CONFIG]5382[/ATTACH]

Yes, this is the correct result. They are simply weaker, as they should be.

optimize atmoshperic OFF
[ATTACH=CONFIG]5383[/ATTACH]

This is the wrong result - you can see that the light ray intensity gets "reset" to full strength as it enters and leaves the prism, which is incorrect.

Best regards,
Vlado

[Guest]

I just downloaded that test scene to have a go myself and the render times are crazy. GI seemed to be off as well is this normal for caustic tests? I am trying to replicate the changes Vlado suggested but I cant see the effects without rendering which is taking around 3 hours

[Deflaminis]

Excellent thread.

[Guest]

I have read that caustics display/calculate better using point lights rather than Vray plane lights as these cast light over a large area. Is this till the case with Vray directional parameter?

[Guest]

I have been trying to replicate the scene by Mnietek2707 but I am having little success with Vlado's comments. With optimize atmoshperic effects off it renders fine but with it on the dispersion effect is completely gone.

I have also used the exact same settings as the file posted by Mnietek2707 for my scene included scale and my results are far worse and splotchy. I am using a prism shape that has no subdivide modifier on it thought but I don't see how that makes a difference?

Vlado, could you offer an explanation as to what's going on? I have attached my scene file also.




Prism_2012_04.zip