Indigo Renderer Forum

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.

Gamma is adjustable using the texture exponent wich is hopefully exposed someplace.

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

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).

In Indigo, select the 'Background Settings'' and see the texture editor for Emission.

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

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.

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

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 ?

Interesting, do you plane to expose this in exporters?

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

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

William wrote:Does not appear available for environment texture in blender (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...

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?

Polinalkrimizei wrote:And whatever "c" does... well, actually I don't even know. Forum search will help, but why so hard?

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