In This Thread bagginsbill said "If you have render gamma correction enabled, you have to set the gamma on transmaps to 1."

Ummm, okay, what does that mean? Is that to say that all transmaps in Poser Pro 2010 have to be set to "use custom gamma" in the image loading options for the trans channel?

They look better that way, as opposed to using the render settings gamma. Why is that?

if you gamma correct transmaps or displacement maps or bumpmaps, you alter the values of the maps and therefore their effects on the model. eg, a transmap works on black and white and grey. if you GC it, you alter it's effect on the model from what was intended.eg - an area which was supposed to be masked out, can then only be partially masked. or a displacement (I learnt this one!) can be reversed.

I hope this makes sense (or someone can explain it better)

Because the values are not luminance values. They are transparency factors.

But Poser was not set up to make that decision on its own. I dont' know why. It is left to you to figure out which maps are transmaps. This seems wildly silly to me but it did make the coding and testing easier.

Luminance values (what are in the RGB values of things we look at) are not linear. Rendering with render GC tells Poser you want to convert everything to linear first. This means that all values less than 1 become lower, because they were gamma corrected in the first place so they look right. This is defined by the sRGB standard - that the response curve of pixels on your screen is nonlinear. There are lots of good reasons for this, mostly having to do with two things: how humans perceive luminance, and how computers encode luminance using only 256 possible values. If we strictly dealt with 256 linear values, many of the higher ones would "look" the same to us, and the fine gradations in the lower ones would look crappy. By "bending" the response curve, it creates a more useful distribution of luminance across the 256 possible values.

But - height maps (bump and displacement), normal maps (which are actually vectors), and transparency maps are not colors. They are numbers just as they are. They are not "sRGB" values. They should not be interpreted the same as color maps are.

So we need to prevent the anti-gamma correction that is applied to image maps, but specifying that they already have a gamma = 1.

There is a script in the scripts menu that does this in just a few clicks for all trans+disp+bump maps across everything in the scene. Use it. It's in Material Mods/change gamma or something like that.

Damn....

Wow that right there explains alot, and I thank you much!

I was wondering what that script was for, hadn't really looked into it because I was just assuming it was a quick way to adjust the overall gamma, which didn't make any sense at the time since it can be done in the render settings.

Oops. ;-)

Thanks for the detailed explanations. I should have realized that, just didn't really ever think about it.

There is a small "gotcha" on using that script.  Some people have used diffuse map as bump also and script will apply gamma of 1 to that map.  It is not good practice to make shader that way, but it is done.  If you have surprising result, then check

Thanks Medzinitar.

I typically use all my own textures though, or rather textures I've bought but modified, and I don't ever use a diffuse color map in a bump channel or any other channel that uses grayscale.