fixing distance shimmer in a forest.

[super gnu]

fixing it is relatively easy.. just crank up the dmc aa max rate and drop the noise threshold nice and low.

the problem is now the foreground of the scene renders incredibly slowly and doesnt need such high aa quality.

dropping the subdivs of various effects and materials doesnt make any difference, as the aa max rate is so high its overriding all the subdiv settings.

assuming i cant split the render into foreground and background.. any other options?

a z-depth control on the sampling quality would be amazing, as i could have more sampling done in the distance..

or alternatively per-object sampling quality?

is this achievable?

either of those two could probably drop my rendertimes by 75%

the dmc system is amazing, but it has its limitations. once you have a low noise threshold and a high max rate, it seems impossible to optimise other elements of the rendering process.. or am i wrong?

[joconnell]

Yeah in some ways adaptive subdivision has a nice ability to drive it's sampling based on face angles too as well as colour so you might have greater flexibility in having high aa on edge samples and lower aa in the middle of an object. I'm presuming your shimmer is being caused by leaves and other such small details in distant trees?

[super gnu]

yes it is. the problem i have is im supposed to be demonstarting what can be done in one render pass with vray. everything was going fine until i cleaned up the forest shimmer by bumping the aa to 1,100 and dropped the noise threshold to 0.002.. the forest looked very nice then, but im having to gradually drop back the settings, as im realising how slow the whole scene renders just to get that one area right.

i managed to cram displacement (2d and 3d) glossy reflections, motion blur, vray fur (just a little) trees with vray2sided on the leaves, env fog clouds, and used the "use irradiance map" tickbox to give just the moving elements per-frame gi. looks amazing and at default aa and noise renders in about 5 mins a frame.

its a shame because it could look lovely, but those shimmering trees kill the look.

i might try adaptive subdivision, but i dont have much hope it will be faster/better on a scene like this, since in my experience it never is! probably ill end up turning off motion blur, but its very frustrating, as i know it could render much faster with all these effects on, if only i could use less samples on everything but the distant trees.

[super gnu]

vlado... z-depth based noise threshold or somesuch thing.. pleassse! would be a huge speed booster in cases like this.. lol maybe a map slot next to the noise threshold.. i could just stick a falloff map in there :P

[joconnell]

Yeah I don't think adaptive subdiv would be better it's just the fact that it gives you options to change your sampling quality based on both colour (maybe material?) and normal threshold (geometry) so you'd at least get the option of dropping sampling on your materials / centres of objects and having higher settings on the edges which are the bg parts causing you all the pain. If anything turning off motion blur might also introduce pixel shimmer with your tiny details slipping in and out of pixels in the background so while you gain some speed in render time, you also introduce an optical problem. Oh for an easy life

[super gnu]

so i was playing round with the shade map, since it was stated it speeds up DOF calculations. no mention was made of motion blur but i just tested and it appears to accelerate that too.. anyone else played with this? am i gonna get glitches on me final render?

edit: just realised there is a thread which mentions it does accelerate mb. however im not sure it is enough of a speed boost, since the motion blur doesnt add a huge amount to the rendertime.. need a lot of testing i dont have time for, to find out.

[chrisjacks21]

Hey super gnu,

did you find any solution for reducing your forest shimmer without increasing render times significantly? Having the same issue here at the moment, and guessing its tiny distant leaves on trees/plants. Suffering large render times so had to knock noise threshold back abit to speed things up (0.00, although it wasnt much better on 0.005. AA is on adaptive DMC 1 & 6 (did have it on 1 & 8 and again, didnt improve too much but slowed down a lot).

I have had to bosh this animation together pretty quick so not had too much time to finetune. I have used trees/plants from the iCube collections and dropped them straight in without paying too much attention to the materials - having looked I see all the leaves have glossy reflections which I guess could be slowing renders down somewhat, the subdivs are on 8 or 10 - could it also be causing the noise?

I have GI ambient occulsion on, can that cause any shimmering on such fine details or not? *scratches head*

cheers!

[Morbid Angel]

to reduce the shimmering effect you do not need to drop the noise threshold or raise max samples. What you need to do is to raise min samples. For any scene with fine detail usually min of 3 samples works.

[chrisjacks21]

to reduce the shimmering effect you do not need to drop the noise threshold or raise max samples. What you need to do is to raise min samples. For any scene with fine detail usually min of 3 samples works.

thanks Dmitry, seems obvious now you mention it! guess I will just have to monitor render time increase...thanks!