LWF Questions

[Per-Anders]

Every single color (including those in all shaders, in gradients and noise shaders and so on) and texture needs to be converted into "linear" color-space, you do that by setting each value to the power of 2.2 assuming you want to use gamma 2.2 as the target, for all colors with brightness sliders you need to factor the brightness slider in too. Every bitmap needs to likewise have a gamma of 2.2 applied (or in your terms a gamma correction of 0.454545454), then to bring it back into monitor color-space you will need to apply a color correction post effect with the gamma correction set to 2.2 (this in fact sets each pixel to the power of the inverse x^1/2.2 = x^0.4545454545~). Then the final result is going to be a LCW gamma corrected image, dont' forget to also do lights and all the material channels, and object dependent colors (Object Color) and so on too.

[paulselhi]

How would you go about correcting lights for LWF ?

[Per-Anders]

The same way for everything else, all color values all brightness values and so on. That goes for all objects/materials/shaders and so on.

It's a lot easier to just use a plugin like DeGamma to do it all automatically for you though as it helps reduce the potential for mistakes, all manual LCW images I've seen show a lot of non LCW mistakes just because there are so many parameters to change and you can't really take shortcuts (you can't just slap a gamma filter on each channel of a material for instance to get LCW because then the shaders aren't working in linear color space so it comes out incorrectly).

[lllab]

for HDRI you have a direct gamma setting in c4d.
set it to 1 instead of 2.2

cheers
stefan

[ThirdEye]

Get DeGamma, costs almost nothing and makes renders look better saving a lot of hassling.

[K1aymen]

I had no idea you had to correct lights too.

Does this apply to speculars as well?

[StefanB]

How can I change the gamma value of a light?

Does this apply to speculars as well?
Yes.

[Per-Anders]

How can I change the gamma value of a light?

You don't. If you could then the result would be as if you weren't using LCW at all. The idea is to get correct light transport and color calculation for your destination colorspace (usually the monitor's gamma or print gamma), which means the lighting needs to keep the same falloff curves, contrast and so on as you've already chosen for it. All you do is modify every color in the light with the same value^gamma evaluation, in the lights case taking the brightness slider into account is really an optional choice, in DeGamma it does, but can be turned off via the filter if the effect is undesirable.

Ass LCW is a workflow rather than something you should apply after the event though then working this way is both laborious and it's going to not give you the benefits, i.e. being able to set colors and things coming out at exactly those colors and brightnesses that you choose, and being able to set up lighting quickly and easily in a far more predictable manner. Effectively manually doing it is like doubling up the trouble of working non-linearly in terms of workflow.

[paulselhi]

Looking at info for other apps and LWF ( Vray in Max for example) they make it appear far less complex than this. Are you saying most others are "fudging" their LWF workflow ?

[ThirdEye]

Looking at info for other apps and LWF ( Vray in Max for example) they make it appear far less complex than this. Are you saying most others are "fudging" their LWF workflow ?

They have a single button that enables LWF and takes care of all these things. Then you just have to change your gamma setting to 2.2 and you're done, kinda like in DeGamma.

[Shademaster]

I have been fiddling around with LWF for a while now and I will certainly get Per's deGamma once we upgrade to 11.5. I have been working in manual LWF for a couple of weeks now and it can be a lot of brainhurt if you forget one little thing. Lightcolors are the biggest problem at the moment and setting every texture to 0.4545 gamma with the filter.

One tip: Do NOT use Filter on a HDR. If you filter a HDR to a lower gamma it will bleach out the HDR in a horrible way! I found this out after it was too late and had to rerender a lot of shots to get it to look okay. Filter a HDR in the HDR tab itself.

[andrasn]

Is DeGamma compatible with Vray? Does it recognize all the different vray material settings?

Thanks,
Andras

[MrBraun]

Is DeGamma compatible with Vray? Does it recognize all the different vray material settings?

Thanks,
Andras

DeGamma don't work with Vray! ;)

[Per-Anders]

Actually it should strip (degamma) all the colors correctly, however you will need to manually apply a gamma correction filter in VRay after the event. I've still not got around to downloading VRay and doing the testing and fixing up DeGamma for VRay comparability to avoid this.

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