Understanding DMC Sampler

[3LP]

http://www.chaosgroup.com/forums/vbulletin/showthread.php?33385-Universal-V-Ray-settings-(well-almost)

http://www.spot3d.com/vray/help/150S...nisettings.htm

Stan

[greysheep5]

http://www.chaosgroup.com/forums/vbulletin/showthread.php?33385-Universal-V-Ray-settings-(well-almost)

http://www.spot3d.com/vray/help/150S...nisettings.htm

Stan

thanks stan!

yeah, we know them and use a variation of those in our work too. but i was curious about peters settings, if they were exactly like the above mentioned or some tuned to personal use variation like ours is...

[3LP]

Hey guys,

what are you thoughts about fine geometry animations?

I mean, I'm trying to render a aerial forest here, and it seems that those settings are not really applying here, the trees are flicking quite heavily and I need to go really low on the noise (ie : 0.005) to get the flick free render, but then the render time is going through the roof.
Is there any reverse way of doing : fine edge AA high but keep it low on the lights/mats/gi etc?

I'm just guessing that the settings for animations are not the same optimization as settings for stills...

Thanks

Stan

[peterguthrie]

thanks stan!

yeah, we know them and use a variation of those in our work too. but i was curious about peters settings, if they were exactly like the above mentioned or some tuned to personal use variation like ours is...

no just the original ones Vlado posted way back (adaptive at 1.0)

[joconnell]

One relevant thing to that is Vlado has pulled back from using 1.0 as the adaptive amount as low amounts of initial rays weren't giving vray enough information to make good decisions and so it could prevent clean sampling - try 0.9 instead.

[Morne]

Try this as an approach when optimizing:

1. Put on a grey override and hide all scene lights, turn off GI. Turn on default lights in the global switches so you get nothing but a boring grey render in your viewport. Use your sample rate element and max adaptive dmc control until you get clean enough edges on your geometry and get a nice looking sample rate with red only where it's needed.
2. Turn off default lights, turn on your scene lights and gi. Leave your grey override on and add in the raw lighting and raw global illumination passes. You know that your AA is probably in a good place now so lets not touch that. The sample rate element might go red again due to your lights or GI adding in noise but don't touch your AA. Try instead adding in more subdivs to your light sources so in the controls of the lights themselves and in the subdivs of brute force GI if you're using that. Change those settings until your raw light and raw GI are nice and clean (if you use irmap and LC instead of touching brute force then the raw gi is less important) and now when you go back to your sample rate then you should be back to having red only along the edges and blue everywhere else.
3. Turn off your material override and turn on the reflection, raw reflection, refraction and raw refraction elements. Again since these will likely be noisy, your sample rate element will go more red due to the aa sampler trying to clean up noisy materials. Again leave your AA as is, and gradually increase your material reflection / refraction settings until the render elements look clean and your sample rate has returned down to the usual red edge, blue everywhere else type of look.

I'm on an interior project at the moment where I went for this approach. I can't show any visuals unfortunately.

So in my tests I rendered at 720p. I started of with IRmap, but then thought I would push it and started over with BF.
My AA is 1, 6
To clean rawlight I had to set the Lights subs between 64 and 128 for various lights. Lights are NOT set to store with ir and also NOT set as skylight portal. Most of them are set to invisible and to NOT affect reflections.
To clean the GI I went with 196 BF subs

With the grey override, everything looked super clean and at 720 it rendered about 1 and half hours. Perfect sample rates and RAW passes etc.

OK Perfect.
I previously set the material samples for glossy things between 64 and 128 to clean it up with IRmap, but when switching to BF I just left it like that.
OK so instead of testing how the sample rate would look now that I switched OFF override, I thought I would just render. While I'm at it I thought ok settings seem pretty good, let me while I'm at it push the resolution up to 4K.

OK so previously with the override at 720 a perfect render took 1,5 hours.

NOW:
Without the override and at 4K everything looks super clean and looks AWESOME!. Just my RAWReflection has some noise in it, but I have to nicely look to see it.
Yes! everything is perfect?
Almost, the part that rendered looks great.

MAJOR PROBLEM!?! After 15 hours rendering it did only about 5% and the estimate said still another 300 Hours to Go!


Aaarrggg!

Any thoughts? I Would love to get this to work with BF.

Suggestions, comments, and general sympathy welcome

[joconnell]

Ha!

What might be happening is now that you've introduced your materials, they're making your lights contribute less to the overall sampling - if you had a flat grey object then it's nothing but lights / shadow samples controlling it's cleanliness. When you put the materials back on, you could be now getting 50% of the final result from light samples but the other 50% from material samples. I'd drop down to 720p again and pick a region of the image that represents your materials and then tweak your material samples. What type of scene is it? Interior / exterior and what's it lit by?

[Morne]

It's an interior mall near the entrance looking out. The entrance has 8m high glass and about 15m wide. In my view this entrance sits on the right and makes up about 10% of the image. The main focus however is inside and looking at a counter and stuff hanging from the ceiling. The outside is lit by a VRaySun with deafault settings. Also, I've got a domelight with VRaySky in it and samples at 128.

Inside the place is lit by large "fake" vray lights to light it up a bit. These lights are about 4meter X 3meter. Here and there there are some VRayIES lights near the walls. Shopfronts ar full height glass and you see into the shops also (no fake shopfronts)
However inside the shops I've positioned large banners with mannequins in front so you dont see much in the shops. Marble floor. Shiny columns between shops. Main mall light is cove lighting made with VRayLightMtl applied to it. So it comes out a bit dark and therefore the large fake vraylights. Exposure is such so that the outside just just starts to blow out slightly, and interior is nicely lit. The sun shines away from the entrance, not into it.

Most Lights are between 64 and 128 samples. Have one large vray light shining down from ceiling (fake light) Have 1 large vray light the size of the shopfronts inside each shop shining towards mall, double sided tick, about 8 of these.

EDIT: Also, in theory then John, could I cut most of my light samples in half then?

[joconnell]

You've a nasty situation full stop here, I'd be inclined to go back to irmap and light cache. Use light cache to accelerate glossies, and turn off the filter on it too - it'll speed up glossies a lot (thanks Lele!).

The light samples you've gotta judge in conjunction with your reflection samples, as noisy lights can lead to noisy reflections. If your sample rate has gone way more red when introducing your materials back in, it might mean your material samples need to go up.

[Morne]

Should I switch off the filter and also the pre-filter?

The thing is that I might need an animation of this area with moving objects, that's why I'm giving BF a go, but obviously might have to go IRmap like you say and just live with that and attempt BF on next scene...

[joconnell]

Ah okay - are you delivering print or animation for this? I'd go irmap for the print, the animation is a whole other world of hurt

For light cache the prefilter is okay, lele recommends using a pretty high value for this - around 250 I think? The filter drop down menu gets set to none. Retrace threshold on also.

[Donald2B]

That's an interesting way to setup the LC. Any more info about why those settings are used and what benefit they provide over using the standard filter?

[joconnell]

Pre-filter gets done before rendering, filter gets done as it's rendering. Filter will slow down calculations a tiny bit to start, and if you're also using light cache for glossy rays, the filter slow down also has a knock on affect on the light cache glossy ray acceleration.

[Donald2B]

Okay, that seems to make sense. So how do you go about making sure you have enough samples in your light cache?

Typically, I would set filtering to none, then render with LC/LC and no AA to see the sample values and size. Then I would just adjust the filtering to smooth the samples out to a nice clean light distribution.

So now, just leave filtering off and once you have the light cache samples level figured out, play with the prefilter values until it is smooth and clean as above?

This stuff makes my head hurt! Just when I think I have a handle on this stuff, something different comes along!

[joconnell]

Sounds about right! Lele is the expert on this though, he used it for all of pixomondo's shots on oblivion. I'll mention the thread to him and he can chime in!