(VRAY) Rendertimes using animation prepass mode

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  04 April 2013
(VRAY) Rendertimes using animation prepass mode


Iīm currently working on a rather complex project, with a lot of shots containing camera movement as well as moving objects.
Since this was my first time rendering an animation with vray, I tried to follow this tutorial on flickerfree animation:


I skipped the Lightcache and only precalculated the IRMap, since it looked good enough without.
Precalculation times were ok, with around 1-2 Min. per Frame at 720p.
But when it came to rendering, my render times exploded.
Before , if I rendered the shot without moving objects and just a precalculated IRMap for the camera path, i had times around 5-10 minutes per frame, now they went up to 30-60 minutes.

Is it that much worse using a prealculated Map per frame for everyone, or is it just me?

Since Iīm on a tight deadline, I just movedd on with some trickery and excluded all moving objects from Gi and tried to light them separately.
But Iīd still like to know how to tackle future animations without staying away from GI....
  04 April 2013
As a little tip for animations, if you're using VRay Material for your shaders, there's a little check box called "Use Irradiance Map" or something like that. If you uncheck it, then any object with that material will use brute force whilst the rest use the IR map. It can be quite a handy way of getting it all out in one render without pissing around with different lighting set ups, but of course Brute Force is rarely quick and you may end up needing to uncheck this box on a lot of materials (because it's not just the moving object that matters, but also the objects catching its shadows, depending on the movement involved).

As an aside, I've never experienced a problem like what you are mentioning. Once the IR map is calculated, I've never really found much difference between From File or Animation (Rendering). The only possible thing I can think of is that, if you're using a render farm (and since you said this is your first experience of doing an animation with VRay, I'm guessing you aren't using much of a farm?) then it could be the fact that the nodes are all grabbing multiple IR maps for each frame (as they need to load the map precalculated for that frame as well as the maps either side up to your interpolation number) and it could be network/drive lag that's causing the delay? Not a clue though, you'd need to check the CPU usage to really work out something like that.

  04 April 2013
how many frames you intepolating?
it should not be more than +/- 2 frames, maybe thats the problem?
very strange problem!
  04 April 2013
Weīre on a tight deadline with not enough render power, so Iīm stayin the hell away from brute force...

Well, itīs also not a network/backburner problem, I just copied the precalculated IR-Maps to a local folder and tried to render it locally
The weird thing is: The first frame renders perfectly fine in acceptable times (around 10 Mins for stereoscopic HD), whilst render times for the following frames went up to 6 (!) hours.
Iīm using 2 interpolation frames and 10 interpolation samples.
In the Log Window it says "Irradiance Map loaded successfully and it seems to load the correct maps for the frame it tries to render.
CPU load is at 100 percent.
For some reason I canīt post on the chaosgroups forums, so Iīd appreciate any input...
Iīm gonna do a little test in a fresh scene to see if the problem persists.
Iīd love to get this problem solved, because I donīt wanna start building a setup with all moving objects excluded from GI and rendered separately with an extra light setup...
The project is quite complex and pretty much everything is proxied or xrefed so settin up any such shenanigans is a real pain...
  04 April 2013
Well my brute force suggestion is only for the objects that are moving, and you may find that it speeds up for production purely by dint of you not having to mess with it! But you're right, there's clearly a problem here and needs to be fixed.

The fact you did it locally and it still happened DOES seem to suggest that it's not an I/O thing (as does the 100% CPU load), but the fact it didn't struggle on frame 1 is odd. Out of interest, if you reduce interpolation to the lowest it can go, what happens to the render times?

  04 April 2013
Well, I never messed with brute force til now, problem is that in some shots the moving objects are makingup almost all of the screen (opening doors etc.), so I guess render times would just be too high...
I already tried lowering the interpolation samples to 1, didnīt seem to affect render times at all.
Iīm recalculating the problematic frames, maybe the problem magically disappears...
  04 April 2013
Dont know if this is normal behavior or not (never used the irradiance map in animlation mode)

But with those times its maybe not a bad alternative to just try to use it in normal mode with higher quality settings.

Could you post a frame of your animation, that way its easier for us to help.
  04 April 2013
If by "normal" mode you mean "Single Frame": Thatīs not possible, because that would lead to flickering in the animation.
And since the project isnīt finished yet, Iīm not allowed to post any frames, sorry.
  04 April 2013
Originally Posted by insertmesh: If by "normal" mode you mean "Single Frame": Thatīs not possible, because that would lead to flickering in the animation.

Not necessarily.
There are plenty of cases where just using higher settings can fix it.

In any case i recommend posting your problem on the chaos group forums also, im sure you'll be helped out there.
  04 April 2013
Ok, so the second prepass just finished, unfortunately the problem didnīt magically disappear...:(
  04 April 2013
Are the Vrmap's particularly large?

  04 April 2013
I donīt think they are. Around 1.5-3.5 MB per frame doesnīt seem too much.
  04 April 2013
skipp all that fuss.. here is the setting you shuold use to get flicker free renders.

set your primary gi bounce as brute force and secondary bounce as light cache, for sampling use QMC with 1 min 16 max and 0.005 for noise thres hold.
Now just render. No need to precal your gi and you will have beautiful flicker free images.

You will find that by playing around with different ir map settings you will end up wasting more time in searching for a flicker free solution. brute force although might be slower is a surer way to get predictable rendering.

Last edited by cooperunionstud : 04 April 2013 at 08:08 PM.
  04 April 2013
Agree with you, totally.
LC /I280x720 res/=I000-I500? or even more?
Can you post some render time examples on this way of GI?
For common scene, with no fancy displace or SSS?
  04 April 2013
Well, even though Iīd love to just through brute force at the problem, I just tried to render one frame using brute force and estimated rendertimes were around 2 h...
So considering the amount of frames to be rendered, I donīt think setting up a working solution with IRMap would take longer then rendering with brute force...
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