PDA

View Full Version : Render time progressively slower



M-X
03-21-2012, 03:18 AM
Hi there, I am rendering a walk thru in lightwave 9.6 on 8 core macs and have hit a problem where the first frame renders in 3 minutes and they then gradually get slower and slower by frame 150 it takes 20minutes, If I restart the rendering at frame 150 it goes back to rendering at 3minutes again!
This is a real problem for me any a ideas?

Reco
03-21-2012, 06:23 AM
As far as I know it is because Lightwave is adding more samples. Please take a look at this tread: http://forums.newtek.com/showthread.php?t=126682
Its all there.

Reco

M-X
03-21-2012, 07:12 AM
Thanks a lot Reco, had a look at the thread seems very interesting but can't see anything that mentions 'samples' or the problem I am having, do you recommend I buy the tutorial?

Lewis
03-21-2012, 08:05 AM
Are you using Animated radiosity cache ?

RebelHill
03-21-2012, 08:11 AM
yups... its the radiosity cache for sure.

Cant remember how to fix this in 96... set to locked I believe after fully caching your scene.

biliousfrog
03-21-2012, 08:15 AM
http://www.except.nl/lightwave/RadiosityGuide96/index.htm

Scroll down about 3/4

M-X
03-22-2012, 02:13 AM
This is fantastic, have read the except explanation and it makes perfect sense! I will give the locked setting a go and let you know. Thanks so much!!!!!!

M-X
03-28-2012, 03:32 AM
The key to the problem is set out below in the extract from the except website. We have had to bake the radiosity first, and bingo! see below, thanks so much for the tips.

"If you have very highly irregular objects in your scene, it might be that the cache system keeps adding new samples because areas are per frame seen that were unseen, like grass, trees and so on. The cache may get choked, rendering goes increasingly slower and eventually might become unworkable. In these cases, bake out just a few frames of the animation, enough to have full coverage of all large objects, and then set preprocessing to 'never'. That works well and you'll get a constant render time without choking. The samples will still be generated but discarded afterwards, and thus not create congestion."

bobakabob
03-28-2012, 11:16 AM
Really helpful replies and brilliant links. RebelHill, great tut on YouTube using economical render settings, essential viewing for new LW11 users.

I'm slowly getting my head round using radiosity in animation and would be grateful for any advice about the following. Sorry if it's already something I should have picked up but I'm still fuzzy about the baking process.

I have a scene I imagine is tricky for radiosity which includes:-
* A couple of area lights and 3 volumetric lights one of which flashes on and off.
* A model of a city for background.
* A moving figure walking towards the camera.
* A moving camera that tracks the figure walking towards the cam then swings round to capture the character walking away.

Are so many moving variables in the scene - both camera and character - - plus flashing lights a bad idea for animation using radiosity?

By not using radiosity I can get good renders from between 35 - 45 mins per HD frame, they just don't look as good.

Non interpolated brute force seems out of the question. Interpolated radiosity looks better than standard renders, about 1 hour per frame. What controls should I check? How should I bake the scene exactly with so many variables?

biliousfrog
03-28-2012, 11:41 AM
Really helpful replies and brilliant links. RebelHill, great tut on YouTube using economical render settings, essential viewing for new LW11 users.

I'm slowly getting my head round using radiosity in animation and would be grateful for any advice about the following. Sorry if it's already something I should have picked up but I'm still fuzzy about the baking process.

I have a scene I imagine is tricky for radiosity which includes:-
* A couple of area lights and 3 volumetric lights one of which flashes on and off.
* A model of a city for background.
* A moving figure walking towards the camera.
* A moving camera that tracks the figure walking towards the cam then swings round to capture the character walking away.

Are so many moving variables in the scene - both camera and character - - plus flashing lights a bad idea for animation using radiosity?

By not using radiosity I can get good renders from between 35 - 45 mins per HD frame, they just don't look as good.

Non interpolated brute force seems out of the question. Interpolated radiosity looks better than standard renders, about 1 hour per frame. What controls should I check? How should I bake the scene exactly with so many variables?

I suspect that you could break down a lot of the scene to make things easier/faster. The environment, for example, could be rendered separately from the character and added back in as a background plate.

You could render without radiosity and use ambient occlusion instead, which simulates background radiosity. I'd render the occlusion separately and overlay with the main render pass in post using something similar to a multiply blending mode.

bobakabob
03-28-2012, 02:14 PM
Biliousfrog,
Thanks, yes, using LW as a compositor, doing 2 seperate renders, keeping camera movements the same for both character and environment sounds like the answer. It should give more flexibility that's for sure. Thanks also for the tip on occlusion. One question here... I haven't noticed much difference with it switched on or off in the test renders. Should surfacing nodes be set in a specific way or is occlusion checked in the render going to generally add more depth and authenticity to the texture of the render?