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View Full Version : Rendering time big problem - please help!

manlio
05-09-2005, 10:44 PM
I have this problem and I can't find a solution. I'm making (better I would want) the rendering of a quite complex scene of a vehicle in a track but suddenly passing from one frame to another, the render time moves from 60 seconds to 2 hours per frame! The problem occurs always in the same frames (only slightly different from the fastest ones). I have tested a lot of things (removing reflections, objects, ...) and the only way to partially solve the problem was to hide from the render some very long sweep objects or/and alpha mapped objects that represents some parts of the track. The vehicle is very detailed and has a lot of reflections.

The machine has 1 GB of RAM and is based on dual Xeon 2,8 GHZ. I have tested the same scene on another PC but same problem occurs.
During the rendering the ram consuption is about 600 MB to 800 MB so it doesn't seem a memory problem, but I'm not so sure. Maybe doubling the ram can help? Any advice?

Other data:
the scene contains a lot of alpha map and 580000 polygons and about 5500 objects.
total number of frames
Cinema ver 9.101
Windows XP PRO
I cannot post the scene or images
LucentDreams
05-09-2005, 11:31 PM
are you using radiosity?
manlio
05-10-2005, 07:11 AM
Sorry I forgive to mention. I use a dome light (soft shadows) made with DIcloner plus one light for the sun and a negative light for fixing exposure Only raytracing involved. Thanks for the reply Kai.
RenatoT
05-10-2005, 07:27 AM
It's hard to understand what's the problem without the scene... :(

Are you swapping when rendering? Any overlapped geometry?

cheers
Renato T.
manlio
05-10-2005, 07:47 AM
It's hard to understand what's the problem without the scene... :(

I know Renato but at this moment I cannot share :sad: and by the way, thanks for your help.
During rendering the HD has nearly no activity. About overlapped geometry, maybe. Too many objects and this can be happened, now I'm searching for overlapped objects, but what problem can drive this issue in your opinion? I never had problems like this in the past. The only new thing in my workflow is the fence of the track made with alpha maps. It is a very strange problems because I can fix it in a lot of frames removing guard rail made with long sweep nurbs (now I have remodeled using a lot of objects and instances but in other frames the problem still happens). It seems to me that depend on camera position, but now nothing is sure...

I also tried copy and paste in a new scene, removing plugins and baking the scene with no luck.
thanks for taking the time to read
zoetropeuk
05-10-2005, 07:50 AM
Hi Manlio,

I've had the same problem with two previous scenes I've rendered. 99% of the frame renders in 10-12 minutes and then the scan-lines just stop and the remaining 3-4 lines can take hours.

I've not been able to work it out. I've tried turning off objects, reflections, etc. But as soon as the scan-line hits the same part of the scene it comes to a screeching halt.

Sorry I can't help solve your problem and a big problem it is. I've submitted the scene to Maxon a while ago but never heard back :(

Matt
RenatoT
05-10-2005, 07:58 AM
"now I'm searching for overlapped objects, but what problem can drive this issue in your opinion?"

only a try. If you try to render 1000 poly overlapped the routine that check for intersection of the rays loose speed. Same 1000 polys in a differente position is a lots faster.

The prob i think is the number of polygons concentrated in a little zone but i can only suppose without the scene :(

cheers
Renato T.
manlio
05-10-2005, 08:33 AM
Thanks for your help guys.
@ Matt
(My right name is Manlio not Manilo, but this is not a problem :D ;) )
I'm sad to hear this thing from you because it seems the same problem :argh:

@Renato
Thanks for the explanation. I'm a really ignorant..

Hope to fix this problem.
Ciao
Jonj1611
05-10-2005, 09:31 AM
Hi,

Have you made sure you haven't got any nested hypernurb objects?

Jon
manlio
05-10-2005, 10:48 AM
I have checked, no nested Hypernurbs. Thanks for the hint.
Sneaker
05-10-2005, 12:24 PM
Are you using any kind of motion blurr?


Michael
manlio
05-10-2005, 12:40 PM
No motion blur. The only post effects is a sun lens flare, but it doesn't (significally) influence render speed. Thanks.
JamesMK
05-10-2005, 12:49 PM
Is it possible that those sweep objects have an insanely high subdivision? - like some accidental change you've made at some point... or even more incredible, an accidental keyframed change in nurbs subdivision... intriguing.

Incidently I've rendered a lot of very long sweep nurbs just the last day, 325 frames with scene motion blur and lots of refraction and reflection, PAL resolution... and I too had a slow-down, but not even close to what you've had here - mine went from ~3 mins/frame to ~8 mins/frame, but that's probably just natural changes depending on camera angle and so on...
Rev9
05-10-2005, 02:20 PM
Try lowering the number of rays to about 5 or 6 ( or the very first number that your alpha chanel doesn't go black on.) and drop the shadow and reflection numbers to 2 or 3. It could be that at a specific angle you get max recursion of reflections which would run 15 times at standard render settings.

But a slowdown of of 120x?????

Best
BT
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