Adding vray light portals - obsolete technique with newer vray builds?

[PIXELBOX_SRO]

Hi guys,

now with all the new sampling and changes to lights etc, will i actually benefit from using vray lights set to portal mode, especially when using vray HDRI map in vray dome light?

Thanks!
M

[PIXELBOX_SRO]

Done some tests and in RGB pass there is no change , however the sampling rate pass looks better.
Wouldnt it be better to get rid of the skylight portal then?

[Alex_M]

And to add to this, I noticed that when using light portals it's better to put the HDRI in the Environment slot in Max/Vray instead of a Dome light. The render just looked less noisy for the same amount of time. That's from a quick test I did. Maybe I should double check or just try yourself so please don't quote me on this.

[vlado]

And to add to this, I noticed that when using light portals it's better to put the HDRI in the Environment slot in Max/Vray instead of a Dome light. The render just looked less noisy for the same amount of time. That's from a quick test I did. Maybe I should double check or just try yourself so please don't quote me on this.

While this may work occasionally, it is not a rule and I would not recommend it. It may easily have come out way noisier, depending on how bright your HDR is.

Best regards,
Vlado

[PIXELBOX_SRO]

So whats the conclusion Vlado? Is it necessary to use them still or whats the benefit nowadays? Perhaps theyre only useful in some situations?

[Deflaminis]

Does that mean the portal will amplify any rays that hit it from behind, regardless of source? I thought it was only environment rays (based on wording of the help, which I may have misunderstood.)

[vlado]

Does that mean the portal will amplify any rays that hit it from behind, regardless of source?

That's the idea, generally. There are some issues when using portals together with a dome light though - the resulting illumination might not be entirely accurate. This is fixable and the fix is somewhere in a GIT branch in our code, but it's not in any release yet. Hopefully I will be able to finish it for 3.6. For the moment though, if you are using a dome light, then it would be better not to use portals at all.

Best regards,
Vlado

[Deflaminis]

That's interesting. Makes sense, thank you.

[LudvikKoutny]

I never used portal lights in combination with dome, because of bad experience that stuck from mental ray, where combining IBL with portals causes more noise and worse quality. In V-Ray, I always thought that portals do not have importance sampling, so they come out very noisy when using high contrast HDRI. I had absolutely no idea you can combine portals with dome to get importance-sampled illumination from portals :O Why isn't this documented anywhere? :O

[leo.surrealismo]

vlado,does the issues when using portals together with a dome light still exists? or is it safe to use it with 3.6?

[vlado]

vlado,does the issues when using portals together with a dome light still exists? or is it safe to use it with 3.6?

There are still issues. Which is partly why I want to get rid of them

Best regards,
Vlado

[LudvikKoutny]

Well... Corona has quite good portal solution, which also works very well with HDRI environment lighting... so perhaps...

[kosso_olli]

They are already working on exactly that, as far as I remember.