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Alex Lovett
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Tags: - C4D - Vray - Maxwell - AfterEffects
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Finally made a breakthrough regarding auto-exposure. I've found that AE can with expressions sample the average brightness of a sample area, thus allowing me to do the math.
I've created a very rough example of this here, so check the link below for the movie:


It needs a lot of work, for a start the averaging code work linearly, but our eyes see light exponentially/logarithmically. So the perceptual average brightness is not the same as the calculated, which skews it a bit.
But It's a good start! And I already have a few ideas how to improve it greatly.

Ok, new day, I've found a nice model of a House, fixed it up a little, boarded some windows up all in the name of testing and fine tuning my auto-exposure expression.
I've rendered it at super super super low quality and It's takingaround 20-30 seconds per frame. Below is one such frame after some fine post work by AE:







That looks strikingly good considering all I did was put a physical sun/sky on and hit render. The realism really is down to the color correction, it looked kinda crap before I did the post work in AE.
Should look even better if I can find a way to batch Maxwell Simulens it.

Well my auto-exposure expression is pretty nice, and it helps a lot, but It's kinda shit too. It's going to take a huge leap of math to make it work properly and not just based on guess work.

Working like this is HARD, you have to be so careful with color profile and linear light, everyone and their dog wants to fiddle with the HDR before you get to see it, and to make matters worse, when I work in what I believe is the correct linear color space in AE, it... looks fantastic in the realtime viewport, but If I hit render.. I get a different result!?!?!?

Clearly even Adobe have a hard time with this color stuff.... fantastic...

--

Ok I've figured out how to do this now in theory, I just realized a checkbox on the exposure effect alter It's behavior, bringing it in line with what i'd expect whereby an exposure of 2 versus 1 results in doubling the average brightness of the image. Now I just have to figure out the math to work that out in reverse... I know it will involve log() in someway.... I really can't wrap my head around the math... *hunts for math geeks AGAIN*



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