HDR vs sIBL

[Guest dialog]

Anyone familiar with how to set up sIBL in 3DS max 2014 with the VRay beta 3.0?

Is there a benefit of sIBL over using a dome HDR?

 

Just curious to this...

[RyderSK]

There is parameter right inside VrayDome that specifies texture resolution, by default it is 512px, so by default it only samples light from 512px downsampled image and renders reflection and background the native resolution. There is no need to manually set it up any different way.

[Guest dialog]

I always change my dome light texture sample so 2048...I have 10 major interior renders I need to do of a highrise and high end condos... just want my work to look like yours Juraj haha

 

So there is no need to look into sIBL stuff?

[RyderSK]

Such high resolution to sample from might yield very little benefit, esp. when you use it simply to produce GI for interiors.

For example, the last project I published, the Icelanding house, had light sampled simply from 360px. The environment was though around 14 000px I think, and that served for reflection and environment, but wasn't necessary for light sampling. Now, that was Corona, but all these principles apply across. Leaving the VrayDomeLight at default 512px works best in 95perc. of scenarios. Architectural scene is probably 99.9perc.

[Chris MacDonald]

Totally agree with the above. Increasing it rarely yeilds any significant boost in terms of quality, and often slows renders down considerably.

[Guest dialog]

That's good to know. SO as for HDR vs sIBL set up is there really a point in using sIBL set ups?

[RyderSK]

It sounds really confusing "HDR vs sIBL" sIBL is simply "smart"Image Based Lighting, a system coined by the website HDRLabs and its founders. It's only general principle how to use IBL in most efficient manner without any particular renderer in mind.

 

Each renderer integrated IBL in different manner, some easier (almost every pathtracer like Maxwell and Corona), some harder/weird (Vray with it's odd "DomeLight" system) some almost non-existent (nativeMentalRay),etc..

 

Vray already does the same that sIBL advocates, it down-samples the actual HDR image to save on rendering time, internally by its DomeLight system. That's already "sIBL". There is no further tinkering necessary, no wheel re-inventing.

[Guest dialog]

Well that solves that ..... Thanks!

[salvador]

Glad to have this so well explained. That's why, you often are offered different resolution HDR's of the same place. Lower HDR res. for lighting and Higher res. for reflections, overrriding reflection / refreaction of course, am I right ?

 

AFAIU, V-Ray will calculate light much faster with a lower res HDR to proccess, whereas loading a heavy 14k HDR for reflection / refraction won't affect the render time that much because it will pretty much be acting as a background.

 

Correct me if I'm worng. Thanks Juraj, helpful again .

[RyderSK]

Well it will affect it, though not such great extent and you can't compromise reflection/background clarity if that's something you want directly visible :- ) [like in space with lot of windows or exposure to sky, interior/exterior,etc..] While lower resolution will produce almost identical light in most scenarios.

 

It's also not directly calculating anything faster at given settings, but lower res will yied less noisy result so less sampling is needed, so, "faster", but it's rather like more efficient to sample.

 

But almost all renderers are becoming so advanced/efficient in sampling that most of this slowly becomes automatic and almost looses point. But strictly regarding Vray2.4, default 512px is what should stay there.

 

Regarding overrides, that's only necessary if you want to change something about it different to resolution. The DomeLight handles the resolution automatically, it will sample light using the lower resolution (default 512px) and reflex/refract/background at actual true resolution (whatever resolution the HDR has).

 

It really isn't something to look too deply into, outside of the weird concept of "DomeLight" itself (which really is ridiculous) it works just like it should out of the box. 1)Place domelight 2)Insert HDRi)...3)render

[salvador]

Ok, ok. I see. So the noise I usually get with IBL comes from sampling rather than resolution.

 

Oh boy! I need to jump back to my literature. Thanks for the feedback, appreciated

[Rich O]

Hey Juraj, what is so weird about V-rays dome light method?

 

I'm only really familiar with Vrays method so curious as to what other renderering engines use.

[RyderSK]

Hey Juraj, what is so weird about V-rays dome light method?

 

I'm only really familiar with Vrays method so curious as to what other renderering engines use.

 

It's completely uneccesary step. Most renderers (almost every other one) sample Environment directly.

The Dome only brings confusement and trouble here (alpha channel,etc.).

[CliveG]

Vray already does the same that sIBL advocates, it down-samples the actual HDR image to save on rendering time, internally by its DomeLight system.

 

I'm thinking about comments made in this thread and many similar comments that seem to be made particularly with reference to Interiors and the lack of light making it to the interior via windows etc. and it seems to often suggest that there is not enough "light samples" finding their way into the interior to prevent noise etc.

 

Which is sort of proven empirically correct by the noise in my scenes, but I'm trying to understand the theory and most especially as it works with HDRI's and perhaps skyportals as well.

 

For as start as I understand it, sampling happens from the camera, not from the light, in that a primary ray is sent from the camera, through each pixel into the scene and when that primary ray encounters an object in the scene the renderer then begins evaluation of the material , light, reflection, dof, motion blur etc. of that object.

 

Again AFAIU in VRAY depending on whether you're using Adaptive or DMC sampling and the image sampler settings there will be an assessment of the returned pixel value and that of it's neighbours then dependant on the threshold settings and the sub-divs of the the light or material the renderer will calculate whether more samples are required.

 

So none of these samples comes 'from' the light does it?

 

Yet clearly if you light a complex interior with an exterior light you quickly come across issues of noise in the low light areas, so there's a lack of light information for the renderer.

 

With an HDRI / domelight though I start to lose the thread a bit, Juraj mentioned that Vray actually downsamples HDRI images behind the scenes, even though the domelight option allows a texture "resolution" setting (default 512) it sounds like that's not beneficial. So what effect does the sub-divs of the domelight have on this or how does that relate to the HDRI downsampling or why do skyportals placed at the windows somehow improve this "light sampling" in my interior?

 

This is a long post, sorry but it's not answered by the help files in a way I can fully understand and "Google+vray+light+sampling" doesn't do it either... there is some good reference out there but there is also a lot of the "bro-science" out there which with some of the comments I've read here from the more eminent contributors seem to give me more questions on this subject than I can find answers for.

 

I'll pre-order Juraj's book on making sense on HDRI application.....

[ichii]

I only know HDR