Adaptive Subdivision vs. Adaptive QMC

[percydaman]

So Im noticing just how much more memory it takes to use Adaptive Subdivision versus Adaptive QMC. My question is has anyone figured out what settings you need with the adaptive QMC to equal the quality of adaptive subdivision at say 0,3?

[Morbid Angel]

well...qmc has different setting for its final result. For example qmc will produce a sharper image then adaptive. But it will require more samples for the less noisy picture then adaptive. Because adaptive will produce always soft result. I found that to get better results qith qmc you need to work with qmc sampler. I believe that some where in the instructions to vray it was stated that the two are interconnected. What I found was that buy decreasing the noise threshold from 0.005 (default) to 0.004 and increasing the globals subdivision multipler by 4, (default 1) the result is crisp but with no noise.
Also, I found that when rendering complex geometry (millions of details) adaptive seems to take much longer time then amc. Infact I dont use adaptive anymore.
Anyways it my take on it.
Cheers

[percydaman]

thanks for the info. So what do you use for your AA settings then using the qmc?

[Morbid Angel]

usually 1/4 and default qmc sampler with mitchell natravalli antialiaser. But sometimes I use soften filter with radius of 4.0 (to blend things like adaptive)

[RErender]

usually 1/4 and default qmc sampler with mitchell natravalli antialiaser. But sometimes I use soften filter with radius of 4.0 (to blend things like adaptive)

Ditto

[Gijs]

Mine is defaulted to adaptive QMC as well. That's also advised in the manual when using lots of glossy effects. Once you get used to it, it is very reliable and predictable and your QMC sampler will become your best friend

To get similar render quality you will need to increase your settings though either global or local. If you change it global, you might want to consider to lower the subdiv. settings for irriadiance, since it affects all subdivisions (except lightcache)

[flipside]

I also use QMC all the time.

AA set to 1/4, QMC settings noise th = 0.001 and local glossy subdivs around 30, same or even higher for area shadows.

noise th 0.001 is very high quality, but rendertimes are lot higher than with0.005 of course

[Morbid Angel]

Im wondering if Vray's qmc is the same as brazil's? would be nice if it would.

[percydaman]

wow...ill have to post some results...but I had to really jack up the AA settings with adaptive qmc to get even close to the adaptive subdivision. Of course, like stated adjusting the global qmc settings will improve that...will have to try that out.

[percydaman]

okay this is getting crazy. Heres a test with adaptive subdivision 0,3. QMC settings are default!



Heres same image with adaptive qmc 1,4. Ive gone way overboard with qmc settings. .001 noise threshold and 15.0 global subdivs!.



Load those two up in ram player and scrub them back and forth and you can really see the difference. Ive even tried jacking up AA to like 6,15 and it still doesn't look as good as standard settings with adaptive subdivision AA. Now the render times are alot faster, and of course memory is MUCH lower which is nice, but the quality stinks.

[percydaman]

ive even tried taking adaptive amount to .7 and global subdivs to a crazy 30.0 and still looks like utter shite compared to adaptive subdivision...

[Morbid Angel]

can we test this scene?

[percydaman]

well, I can't post it for everyone to download, but I could up it to ftp tomorrow. (cant upload to ftp at home, my modem quits working when i do for some reason) Email you the download location if youll take a look.

[Morbid Angel]

yeah lets do that

[percydaman]

okay anyone can try this file:



http://myweb.cableone.net/amylenhart...ssytesting.max

have issues getting good smoothing of glossies. Adaptive subdivision just looks so much better with same material glossy subdivision amount.