Render Passes DO NOT = Beauty Pass

[Camby1298]

I've done an extensive amount of searching on this matter, and I cant come up a reason as to why my passes when grouped together, dont equal my beauty pass. There have been similar postings on Chaos Groups forum, but no answers were presented....

 

I rendered out Raw passes, so naturally everything is put together mathmatically correct, but it seems there is an odd gamma shift on some pass....not sure....Its most likely its something simple that I overlooked...

 

Anyways the passes used/and set up are this:

 

Vray Specular (Add)

Vray Self Illumination (Add)

GROUP (Add)

___Vray Raw Reflection (Multiply)

___Vray Refraction Filter (Normal)

GROUP (Add)

___Vray Raw Reflection (Multiply)

___Vray Reflection Filter (Normal)

GROUP (Add)

___Vray Raw Global Illumination (Multiply)

___Vray Diffuse Filter (Normal)

Vray Raw Lighting (Multiply)

Vray Diffuse Filter (Normal)

 

All is LWF. Anybody have a clue, Id appreciate the help, thanks....

[A.Mitov]

I read this somewhere but can't remember where. Basically it was something along these lines - to get perfect results you should render and combine your passes in Gamma 1.0 mode, not LWF. Apply the gamma 2.2 curve (or whatever gamma you like) when you're done combining your passes.

 

That's because When the 2.2 gamma curve gets applied or "burned in" to the different individual passes all the math behind combining the passes gets messed up and the end result will be different. I haven't tried this but I think it makes sense.

 

Try it and let us know if that fixes your problem!

[Camby1298]

Interesting, my exr's are saved out as 1.0 gamma, but with 2.2 burned in as they render, (In my max prefences, my input gamma is 2.2, and my output gamma is 1.0, but my working space is 2.2 gamma) in that my output files from max are defaulted at saving at 2.2.

 

Youre suggesting I change my work space gamma to 1.0 when rendering out, and then apply the gamma shift in post?

 

[ATTACH=CONFIG]45816[/ATTACH]

[A.Mitov]

Brian, I just took a look at your Gamma/LUT preferences. Even though your output gamma in Max is set to 1.0 that doesn't mean that you output your images in gamma 1.0 space (but that doesn't really matter since you render in EXR). That's because if you've set your gamma to 2.2 in "Color mapping" Vray burns this gamma in your renderings during render time. The "output gamma" setting in Max'es preferences needs to be set to 1.0 because if it were 2.2 you would burn gamma 2.2 curve twice - once during render time (remember gamma 2.2 in "color mapping" tab?) and then once again when the image is saved to disk. Once again, this doesn't really matter since you're rendering in EXR.

 

Just make sure that when you pull out your passes, even though rendered in EXR with gamma 2.2, you set their gamma back to 1.0 prior to combining them. Then combine them and just after you're done then apply back the gamma 2.2 curve. I'm not an expert on passes but I'm going by memory so try this and let us know if that solves it for you!

Edited November 18, 2011 by A.Mitov

[Camby1298]

Thanks for help, I have another rendering coming up I can see if that works, FYI I set my Color Mapping Gamma at 1.0, so Im not 'double gamma'ing' my images. My gamma burn happens because I set my prefences to save at 2.2 (as seen in my attachment previously).

[A.Mitov]

Ok great. I'm eager to see if that solves your problem.

[Camby1298]

Brian, I just took a look at your Gamma/LUT preferences. Even though your output gamma in Max is set to 1.0 that doesn't mean that you output your images in gamma 1.0 space (but that doesn't really matter since you render in EXR). That's because if you've set your gamma to 2.2 in "Color mapping" Vray burns this gamma in your renderings during render time. The "output gamma" setting in Max'es preferences needs to be set to 1.0 because if it were 2.2 you would burn gamma 2.2 curve twice - once during render time (remember gamma 2.2 in "color mapping" tab?) and then once again when the image is saved to disk. Once again, this doesn't really matter since you're rendering in EXR.

 

Just make sure that when you pull out your passes, even though rendered in EXR with gamma 2.2, you set their gamma back to 1.0 prior to combining them. Then combine them and just after you're done then apply back the gamma 2.2 curve. I'm not an expert on passes but I'm going by memory so try this and let us know if that solves it for you!

 

 

Hmmm...this made no difference. I did another test rendering with the above considered and the combine elements were still shifted from the beauty pass...bummers

[A.Mitov]

Sorry to hear that. I have no clue then. Maybe some experienced pass composer could shed some light onto this issue.

[notamondayfan]

What software are you using to composite?

 

Also, can you post your Vray Color Mapping settings, and your exr save setup?

 

To me your compositing method and LWF / 2.2 seems fine to me.

 

Dean