HDRI lighting optimizations...

[davision]

As I wait breathlessly for the HDRI dome light... I have some questions about HDRI lighting.

Is there any difference between using a bigass normal-flipped sphere with a self-illuminated material with a HDRI diffuse map OR using an HDRI directly in the environment slot? My simple crude tests say no... but I can't be sure.

Does blurring an HDRI speed things up? And/or reduce blotchiness?

[Sushidelic]

Using a mapped sphere is somewhat slower when rendering (at least in all the cases we tried it here), but has other advantages - you can rotate it in any axis and you see a direct viewport reaction.

Blurring an HDRI will reduce blotchiness if you have very bright and small areas in your HDR image, but it will naturally loose "sharpness" in the lighting as well, as you'll get a more even light - the more you blur, the more it becomes like a skylight. So you could say that it speeds up things, as you'll get away with fewer samples to achieve a clean image for the cost of loosing sharper shadows.

Best thing to remember is that you only need a very small HDRI map to light your scene (256x128 is often enough), and the big one goes into the reflection/refraction environment. There it really can't be big enough, especially if you have some strong and crisp reflecting content in you scene.

Regards,
Michael

[davision]

Thank you. Good tips.

[jujubee]

I find HDR blotchiness is directly correlated to units. If a photo was taken in a real world setting, try to match it up with your scene measurements.

Also, you can view the HDRI if you just use a viewport background and rotate it in the vray mat settings.

[flipside]

Here's an example of blurred hdri maps:
http://www.chaosgroup.com/forum/phpB...ic.php?t=12196


Resizing a map is actually the same as blurring, it removes any crisp detail and extreme bright pixels in the map.

[fewlo]

[quote="jujubee"]I find HDR blotchiness is directly correlated to units. If a photo was taken in a real world setting, try to match it up with your scene measurements.

quote]

Hi,

This confuses me slightly, how can you determine the scale of your hdri map in relation to the scene?

Thanks,

Fewlo