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medzo
03-31-2016, 02:14 PM
Hi

I have a rather simple question.

When I use Hdri in Textured environment for illuminating a scene (archviz), I never really know, should I just leave gamma setting to 1.0 and lower the opacity in Textured Environment or set hdri with gamma 2.2 and also increase the opacity in Textured Environment.

With gamma 1.0 I can get nice sky color, the color of lightning is also blueish, but materials can get to easily overblown (RGB values on rendered image are over 255) due to reflecting the 'sun' in hdri, and with gamma 2.2 the lightning is more yellowish, materials seem more dull, but there are no overblown materials.

I have seen tutorials where some suggest to go for gamma 2.2, but others are using 1.0 (sometimes even 0.75).

What is the right procedure?

Thanks

RebelHill
03-31-2016, 04:09 PM
If you're using it for lighting, then it ought be gamma 1... but if ur using it as a backdrop image, then you want it to match with your scene, which will usually be gamma 2.whatever.

Ofc, the other thing is to use it at gamma 1, use linear workflow, and correct your final renders.

medzo
04-01-2016, 01:53 AM
Thanks RebelHill

I cannot use one hdri for all? Lightning and backdrop image (for reflections and of course background of the render)?

So, the correct procedure should follow:

1. I need to load hdri in image editor, make a clone of the hdri, leave one at gamma 1.0 and other to 2.2
2. Load hdri with gamma 1.0 into Textured Environment and set opacity accordingly
3. Make inverted lumi sphere and attach into color slot the second hdri with gamma 2.2 (diffuse 0%, luminosity value should be something that looks good on materials)
4. In object properties of the sphere uncheck all shadow parameters and unseen by radiosity

Will that work properly?

The other thing that you mention is using linear workflow.

Do you mean just set in ColorSpace panel to linear and then in Postproccesing window set (let's say) FullPrecisionGamma 2.2 plugin?
Wont that also affect VPR? The colors in VPR will be linear but final render will have different colors (gamma2.2), also doesn't working in linear color space messes up adaptive sampling (antialiasing) and final buffers (for compositing)?

medzo
04-01-2016, 02:10 AM
Nope, my procedure wont work. I cannot use Textured environment just for lightning without also affecting the reflections on materials.

How can I make this happen?
I would like to use Hdri for lightning and use it for something to reflect (backdrop image).
Hdri for or lightning, according to RebelHill, needs to be in gamma 1.0, but the reflection map should be in gamma 2.2?

I am starting to believe that I have over complicated a rather simple thing...

RebelHill
04-01-2016, 02:35 AM
Your complication stems from the fact that you're trying (needing) to mix both colour spaces in the scene at the same time... thats not really, or easily doable.

Try this here... for more detail, or perhaps a better way of getting it right, see if you can snag Gerardo's attention.

medzo
04-01-2016, 07:45 AM
Huh, never thought that this is more complicated. I always thought that I had 50-50 chance of getting it right :)

Your approach is giving me washed out textures, probably because my textures already have gamma 2.2 applied.

But I find it strange, for a program like Lightwave, that working with hdri skies is not straight forward. I would expect that everything should work instantly with illumination as well as reflections etc... I mean, it seems that with other programs (like vray, or others) you just load hdri and everything works. Or am I wrong?

RebelHill
04-01-2016, 08:00 AM
yeah, you probably have to flag your texture files as being sRGB... images need to be flagged for the gamma they contain.

As for other apps, vray, whatevs... its no different there if you're trying to mix colour spaces within a single render, you'll get issues somewhere. Your problem is that you're trying to use a single image, your hdri, in both linear and sRGB mode at once, clearly you cant do that, not in any app... its just the way they will be setting up ligthing vs BGs thats probably different.

Actaully... try this instead... go back to CS sRGB preset mode for your scene... load your hdri and flag it as linear in image editor, setup your textured enviro (for lighting). Now set a sphere object, with the hdri as a texture, unseen by lights/gi.no shadows, but seen by camera (this'll be your rendered BG)... but, use that DBW colour node to do a lin>sRGB colour switch before plugging it to the surface colour input.

You should now get proper HDR lightng from a linear map, with a BG rendered from a 2.2 texture.

medzo
04-01-2016, 01:08 PM
ok, I am testing your approach, this could be the right stuff, need to do some more tests.

what about the rays on sphere? should materials reflect environment image (linear) or sphere image (sRGB)?

RebelHill
04-01-2016, 01:23 PM
You want any objects to be reflecting the sRGB version in this whole case, which will mean leaving it visible to rays, and setting amterial reflection options to raytrace only (so they dont see the BG).

medzo
04-01-2016, 03:54 PM
Thanks RebelHill.

My conclusion (based on few test renders on one scene) is that from artistic point of view I like better that materials reflect a hdri image in linear or gamma 1.0 mode. When materials reflect a sRGB image I lose most of specular highlights (to clarify - I only use reflections on materials, no fake specular). The down side of this is that on some materials, depending on view angle, the reflections are too strong.

Just thought that maybe I need to increase luminosity value on a sphere image (on sRGB), maybe I will get some of the highlights back. Back to the drawing board :)

Thanks again

gerardstrada
04-22-2016, 04:10 PM
If done well, HDRIs are scene-linear by nature, so yes it should be set up to linear. It's also recommendable to work with some kind of linear workflow. Otherwise your highlights will be easily overblowed with a HDR IBL solution.

http://s31.postimg.org/j7kiu3aiz/ssw.jpg
(from LW content)

If you are working in the color range of sRGB standard, you might try the sRGB preset in CS panel as starting point.

http://s31.postimg.org/undm6a1hn/lsw.jpg

If still you get superbright highlights you could try some kind of tone-mapping like DP Exposure, DP Tonemap, or probably the Roll-Off or filmic TMO node configurations shared here (http://forums.newtek.com/showthread.php?71751-Extra-Buffer-nodes&p=1436857&viewfull=1#post1436857) and here (http://forums.newtek.com/showthread.php?71751-Extra-Buffer-nodes&p=1473757&viewfull=1#post1473757).

http://s31.postimg.org/xxxubsiyz/lswhc.jpg
(DP Exposure used in this sample)



Gerardo

medzo
04-24-2016, 10:58 AM
Hi Gerardo

Thank you for your setups, I have to admit, that is a little beyond my comprehension.

Do you have any suggestions how to use hdri in textured environment for lightning and a lumi sphere just for reflections?

Thanks

PS: I really hope that LWNext will have this much more simplified :)

gerardstrada
04-25-2016, 12:49 PM
Most of the times it's simpler to enable Importance Sampling (GI panel) and go with a tonemapping operator in post like the ones mentioned before. i.e.: DP Exposure node can be used within DP Node Image Filter.

But if for some other reason you need to separate lighting and reflection components, you might want to try a setup like the one in smartIBL (http://www.hdrlabs.com/sibl/index.html) (courtesy by Christian Bloch).



Gerardo

medzo
04-25-2016, 01:38 PM
Thanks Gerardo

I will try it with DP Node Image Filter and see what happens :)