View Full Version : mia photo exposure lens and SSS

02 February 2011, 05:38 PM
i've been trying to figure out what's happening when i switch from a camera without a mia lens to one i have with the mia photo exposure lens. i have two models that seem to get different results when i switch. it might be something simple since I'm not too experienced in the finer points of rendering. any one hve any ideas?

no mia lens

with mia photo exposure lens

02 February 2011, 07:47 PM
Well, basically, you're applying exposure control as in real-world photography to the image so it's defaulted to the camera's exposure value. Adjust this up or down to darken/brighten the image. Also, have you set Maya up to work in linear colourspace?

02 February 2011, 08:05 PM
i liked the exposure for the guy, but the SSS on his said seems to look strange to me, is that just from the brightness?

the tutorial i'm using for reference uses linear colourspace, but to be honest i'm still not quite sure what it means/ does. so i may have messed something up there.

02 February 2011, 05:07 PM
Yes, it's essential to work in linear space when using physically based effects like photographic exposure. But, when doing so you have to make sure all your texture maps are gamma-corrected or you will not get correct renderings.

02 February 2011, 10:08 PM
alright, so i understand it a bit better now, but Maya 2011 has a setting in render settings window that gamma corrects all your textures automatically unless you specify otherwise. i have this on but my stuff still looks like this, so I'm a bit confused. the mia simple exposure lens doesn't seem to really do this though, just the photographic exposure lens.

02 February 2011, 01:38 PM
what lights are you using? Photometric/light portals/Maya legacy lights?

02 February 2011, 03:45 PM
i have 2 area lights with an mib_blackbody node plugged into the color.

02 February 2011, 05:22 PM
Well if you have everything set up properly as regards photometric lights, photographic exposure and gamma corrected texture files then it's just a matter of tuning the blackbody shader/light intensity and exposure values till you get the desired result, really.

03 March 2011, 04:02 PM
aside from what musashidan said. Do you also turn OFF screen composite in the sss shader?

03 March 2011, 11:24 PM
Also i see you have a more bluish whitebalance with the renders that use the exposure lens, which makes the overall render look more cold. Try adjusting the whitebalance to get a warmer tone again.

03 March 2011, 04:31 AM
musashidan - thanks for all the info, but for whatever reason I'm still not getting it to work. i'm sure it's just my lack of experience. but anyway for now i think i'm just gonna use the default camera since for whatever reason it seems to be working better for me.

SuperHero - yes, it's turned off.

CHRiTTeR - yeah, i think i had it set up to give the true color of the textures, but i might have changed it a bit. my man problem was the weird effect it seems to have on the SSS skin.

03 March 2011, 04:08 PM
I would suggest you do a search on linear workflow on the Maya forums. Lots of talk about it there.
Heres a link to a 3 part video ( tutorial about LWF in general and in Maya.
Basically you need to degamma all your textures and color swatches. Those you don't need are spec, bump and displacement maps. Redsand posted a nice script for easy degammaing (!) all your textures.

As a personal preference I often plug in a blackbody to the whitepoint attribute of my exposure node.
You can try and see if that gives you any interesting results.
Nice renders btw :).

P.S Im still fairly new to the whole linear workflow stuff, and so many people seem to have different oppinions about how to set it up and what works best. Which is why I recommend you do your own research and find out what works best for you. After all, what really matters is the final product not how you made it.

03 March 2011, 06:03 PM
be warned about the color managment on the filenodes, main td here swears they dont work correctly (i think its a great idea though, wish there was a tx make like renderman built in).

when you use a lens node in maya, putting the gamma to 1.0 will show you what your looking for - e.g, the actual render. it sets it to 2.2 by default, which is what you should be rendering at so that way applying your .454 gamma curve in comp will get you back to the image you see rendering at gamma 1.0.

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