Render passes increasing render time

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  03 March 2011
Render passes increasing render time

Having a pretty serious problem getting Maya/Mental Ray's render passes to work properly for me.

I've been getting reasonable render times in the past (about 1 minute per frame), but as soon as I associate passes to a layer the render times go up to about 4 minutes per frame.

I've tried deteling all my layers and rebuilding. Currently I'm only using the masterLayer and even it is giving me the increased times. I've even tried importing everything into a new scene (after deleting all the layers and passes) and redoing all the render settings to no avail.

I can't seem to find threads on any website where other's have had this issue. Can anyone help out?

-Arch.
 
  03 March 2011
the increased render time is cos of your ao pass..remove your ao pass and render time will be bak to 1 frame. i render ao pass separately..also allows me to handle transparency. or you can instead use mia material's built in ao.
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  03 March 2011
Hey lipuster,

I don't think that is the issue. I tested a few of the passes to see if I could narrow down to which one it was. It appears that ALL of them are currently increasing the render times slightly, and when you use all of them it blows the render out massively.

-------------------------

Okay, actually went back and tested your theory a little better and it turns out the AO pass alone is adding about 1 minute to the render times. I think I'll be taking your advice.

That said however, the other passes are still adding an additional 2 minutes to the render times, which I assume isn't supposed to happen. I'd still like to try and get around this if I can.
 
  03 March 2011
that's strange... am pretty sure of the behavious i mentiones and other passes have never incresed my render times at all. and the ao pass (with ao enabled in mr globals too) makes it approximately 4 times. i hope you unchecked ao in mr globals and didnt just remove the ao pass.
regards
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  03 March 2011
another pass that can cause render times go through the roof is the raw shadow pass ... I had problems with this one ...
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  03 March 2011
@lipuster

It definitely is strange, and I'm afraid I'm only going to make it stranger.

I've actually got two animations that need to be rendered. The second one is giving me less issues and it seems your advice on the AO pass was correct. I've pretty well fixed that one.

The first one on the other hand is still misbehaving. I've done some rendering tests to see if I can isolate which pass is doing the damage, and although the AO is partly to blame, it's not the only one. Here are the results:

FRAMEBUFFER: RGBA (FLOAT) 4x32 BIT
   EXR format
  
   No Passes = 1.27
   AO = 2.07
   ambient = 1.33
   diffuseNoShadow = 2.53
   matte = 1.30
   motionBlur = 1.35
   reflection = 1.35
   shadow = 3.06
   specularNoShadow = 1.53
  
   All Passes minus AO = 3.38



Obviously the AO pass is still an issue, but using a material override on another layer fixes that problem.

The problem now is the diffuseNoShadow pass and the shadow pass that are blowing things out. Is there any reason why this could happen?
 
  03 March 2011
What version of Maya? Previously Autodesk poorly implemented their framebuffer system with mental ray using a bad function that increased render times and memory consumption. (i.e. it's not mental ray, other 3rd party framebuffer systems made correctly did not suffer this problem.)

I want to say it was resolved or improved in 2010.
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  03 March 2011
Hey Bitter,

I doubt that's the problem then. I'm using Maya 2011.
 
  03 March 2011
Might be interesting to test with a different framebuffer system but I don't currently have access to one. (Used to but deprecated now)

Might be a case to complain to Autodesk if you have support. just be sure you aren't using any "unsupported" (unexposed) shaders or they won't help you.
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  03 March 2011
Well, even if I didnt test it, there could be an explanation to the behaviour of shadow passes, especially for the noShadowPass.

Normally the lighting is evaluated in a lightloop. From this one you get the light contribution of the sampled point. In this loop the lights that will be blocked by some geometry will be skipped.

But in a noShadowPass you want to turn off this behaviour, and you want the light to illuminate the whole image without shadows. How can you do this? You'll have to shade the point twice. First turn off shadowing, evaluate the point, then turn the shadowing back on and shade the point again. Put the first result into the noShadowPass, the second into beauty pass.

If I'm right, all uses should see this behaviour. If not - well forget what I wrote...
 
  03 March 2011
Originally Posted by Bitter: What version of Maya? Previously Autodesk poorly implemented their framebuffer system with mental ray using a bad function that increased render times and memory consumption. (i.e. it's not mental ray, other 3rd party framebuffer systems made correctly did not suffer this problem.)

I want to say it was resolved or improved in 2010.

I Think you mean 2011
http://mayastation.typepad.com/maya...ed-in-2011.html
 
  03 March 2011
Originally Posted by SePu: another pass that can cause render times go through the roof is the raw shadow pass ... I had problems with this one ...


This has been the most render intensive pass for me as well, even in Maya 2011.
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  04 April 2011
Okay, think I've finally figured out what the issue is, although from what I understand it shouldn't be an issue. Maybe someone can help explain why.

The problem appears to not be the render passes as such, but the 'hold-out' feature I've turned off on the background passes. Switching it off makes my renders take about 10 minutes per frame, with it on they take 1.5 minutes per frame.

Can anyone at least explain why this is the case, or even better offer a way to fix it. I don't think it should be too big a deal, but I'm worried about getting the slight black outline around my character objects once I move on to post.
 
  04 April 2011
Hi,
interesting info there. So why have you turned off the hold out feature (im assuming its on by default..cant check now). is it that you are using pass contribution maps and the turning off holdout prevents the creations of holes (where objects are excluded from ur contribution map ) in the bg??

Regards.
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  04 April 2011
Originally Posted by lipuster: Hi,
interesting info there. So why have you turned off the hold out feature (im assuming its on by default..cant check now). is it that you are using pass contribution maps and the turning off holdout prevents the creations of holes (where objects are excluded from ur contribution map ) in the bg??

Regards.


Bingo lipuster, that's exactly why I'd like to turn it off. It's on by default, which causes the cutout/holes effect you refered to. And this will quite often lead to a black line of pixels around your foreground object where it doesn't quite do the cut out perfect.
 
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