[REQ] hdr environment - gamma control

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William
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[REQ] hdr environment - gamma control

Post by William » Thu May 09, 2013 2:44 pm

It is a common method to adjust the gamma of a HDR environment map to achieve more/less contrast output from the environment.
In some cases this is required to achieve the intended/desired effect from the hdr source.

If possible saturation control for the HDR would also be very useful.

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CTZn
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Re: [REQ] hdr environment - gamma control

Post by CTZn » Fri May 10, 2013 12:20 am

Gamma is adjustable using the texture exponent wich is hopefully exposed someplace.
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William
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Re: [REQ] hdr environment - gamma control

Post by William » Fri May 10, 2013 12:27 am

Gain exponent is there, is this what you meant? It just appears to change brightness/gain.

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CTZn
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Re: [REQ] hdr environment - gamma control

Post by CTZn » Fri May 10, 2013 12:35 am

Sorry I'm not used with the blender terminology, I would not like to add to the confusion.

In Indigo terms, every texture has properties among wich exponent. Exponent is normally the inverse function of gamma, though it may behave just like gamma in our case.

The question is: where can you access the HDR texture's exponent parameter within blendigo.

For some reason the Gamma control within Indigo GUI's texture editor is greyed out (in the material test scene).
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CTZn
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Re: [REQ] hdr environment - gamma control

Post by CTZn » Fri May 10, 2013 12:37 am

In Indigo, select the 'Background Settings'' and see the texture editor for Emission.
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William
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Re: [REQ] hdr environment - gamma control

Post by William » Fri May 10, 2013 12:44 am

Here is the settings for the environment lamp on blender. It just behaves like gain/power.
exp.png
And yes, the gamma in indigo texture setting is greyed out.

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CTZn
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Re: [REQ] hdr environment - gamma control

Post by CTZn » Fri May 10, 2013 8:31 am

Well. In one case it's not exposed and in the other it is greyed out. Last option might be to edit the IGS file after export and before it is loaded.
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OnoSendai
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Re: [REQ] hdr environment - gamma control

Post by OnoSendai » Fri May 10, 2013 8:59 am

Gamma has to be one for HDR images in Indigo. You could use the 'a' texture param though (quadratic coefficient)

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CTZn
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Re: [REQ] hdr environment - gamma control

Post by CTZn » Fri May 10, 2013 12:19 pm

OnoSendai wrote:Gamma has to be one for HDR images in Indigo.
I always thought that tweaking the environment map gamma would allow to cheat with low dynamic ranges.
OnoSendai wrote:You could use the 'a' texture param though (quadratic coefficient)
Bummer why did I never use it ?
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William
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Re: [REQ] hdr environment - gamma control

Post by William » Mon May 13, 2013 5:13 pm

Interesting, do you plane to expose this in exporters?

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Re: [REQ] hdr environment - gamma control

Post by Zom-B » Mon May 13, 2013 6:24 pm

William wrote:Interesting, do you plane to expose this in exporters?
The A, B and C parameters should be available in all Exporters to tweak the texture since quite some time :)
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William
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Re: [REQ] hdr environment - gamma control

Post by William » Mon May 13, 2013 6:50 pm

Does not appear available for environment texture in blender :wink: (see screenshot of setting above)

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Re: [REQ] hdr environment - gamma control

Post by Zom-B » Mon May 13, 2013 7:29 pm

William wrote:Does not appear available for environment texture in blender :wink: (see screenshot of setting above)
Ah ok, got it :)
Blendigo doesn't use a Material for EnvMap but a direct link to a texture instead. That is different in C4D exporter for example...
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Polinalkrimizei
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Re: [REQ] hdr environment - gamma control

Post by Polinalkrimizei » Mon May 13, 2013 8:02 pm

And while we're at it: If "a" can control gamma in an hdr, why not call it gamma control?! Or at least something more intuitive...
And whatever "b" does, I think 99% of the artists use it to determine the height of the bump/displacement effect, so why not give it proper name? If you're new to Indigo, this function may seem reeeeaaaaallllly well hidden :?
And whatever "c" does... well, actually I don't even know. Forum search will help, but why so hard? :x

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Re: [REQ] hdr environment - gamma control

Post by Zom-B » Mon May 13, 2013 8:09 pm

Polinalkrimizei wrote:And whatever "c" does... well, actually I don't even know. Forum search will help, but why so hard? :x
C does a upscale / clamp of all RGB values. With an C value of -0.5 for example you reduce the RGB of a texture by 128. That is nice to clamp values for bumpmaps or exponent maps, so areas of a texture move into full white or black and result in a hard cut contrast.
You also can "flip" a texture by using a B of -1 and a C of 1. Useful for blend maps and others :)
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