V-ray HDRI : dome light - adaptivness threshold

[rollsroll]

Hi,

 

I render an interior scene with only HDRI lighting.

When I use VrayHDRI map like a texture in Vray dome light (with default adaptivness threshold 1,0) I get a nice result.

But if I want to use VrayHDRI in environment slot with skylight portals in the windows, I get completly different result

Is there any way to get the same result, without using domelight with adaptivness ??

[inpow watir]

Frankly, i never used that combination (adpt treshhold =1 + HDRI) in an interior scene.

[Chris MacDonald]

Some images showing what you're talking about would help.

 

However, the VRay dome light uses importance sampling and thus looks right. The environment slot does not, hence you get crappy lighting.

[RyderSK]

Some images showing what you're talking about would help.

 

However, the VRay dome light uses importance sampling and thus looks right. The environment slot does not, hence you get crappy lighting.

 

Yes, but so does Area light was my understanding. But it's true the option not only gets greyed in Portal light, but I guess doesn't function even. A friend (Lasse R) did a fairly broad comparison between variously dynamic maps and eventually env+portal light provided different (read worse) result than domelight itself if the map had particulary high range. It hasn't been my experience, but I just don't have time to re-test myself anything broadly these days.

[Chris MacDonald]

I have noticed that when rendering an HDRI through the environment slot the quality of shadows is pretty bad although it does render quite a lot quicker. Clearly something else is happening, I just don't know what.

[rollsroll]

Juraj is right.

When I do not want to use the dome light and oversample entire scene.

I use HDRI map in the environment slot and place skylightportals to the windows which will sample the interior only.

But the problem is that the environment map + skylightportal doesn´t produce the same light as dome.

This is because dome has adaptivness slot under the tex map.

When you set adaptivness to 0,0 the result will be same as skylightportals, but when you set adaptivness to 1,0 you will never get the same result from skylightportal.

[RyderSK]

It's quite odd behaviour imho, and shows that PortalLight works correctly for indirect/diffuse light only mostly. I've used Sky Portal heavily during years but they're not quite well implemented in Vray imho as instead of simply 'focusing' sampling, they act as actual light sources.

 

For simplicity sake, in Vray3, I opted almost always for pure Domelight recently. It does take rendering toll for interiors.

 

[to avoid confusion Chris, Vray never sampled environment slot for direct lighting, but in theory, that should have been rectified by usage of sky portals, which do provide that sampling, but maybe they just don't, although they improve the quality, but to different visual result than domelight itself alone].

 

Now I am pondering why this is. In theory, all SkyPortal in Vray does, is take color/intensity of what's behind it, either tracing it, or in Simple mode, taking it directly from environment. It work absolute correct when that environment is simple map, color or low-range gradient like VraySky, but once behind is some detailed high-dynamic range HDRi, it fails to reproduce the lighting in quality similar to Domelight. Does it ignore what it doesn't directly see in camera perhaps ? Does it blend it too much (it no longer accepts resolution, no only adaptivness) ? Well, who knows. I can't and won't test it.

[Ismael]

V-Ray 3 Help:

 

"Advanced

 

These options do not generally need to be changed. They are used in very very specific situations.

 

MIS - this option allows to disable Multiple Importance Sampling for the light. When MIS is enabled (the default), the light's contribution is split between direct illumination on the one hand, and GI (for diffuse materials) or reflections (for glossy surfaces). This means that portions of the light's contribution will end up in the GI render elements (or the reflection render elements respectively). In certain specific situations this is undesirable and this option can be used to always calculate the light contribution through direct illumination.

Icon

 

Disabling this option may increase noise, especially in glossy reflections. Only disable it when you have a reason to."

 

 

My comment: Disabling, you'll have to add a Vray Sun. As for Skylight Portal, a VrayLight at the window is faster.

 

http://docs.chaosgroup.com/display/VRAY3/VRayLight#VRayLight-DomeLightOptions