View Full Version : Render times - get longer by the frame...?

05-04-2003, 07:45 AM
Hi People!

I'm trying to render-out an animated short, roughly 1200 frames in length. I've got render times down, even with Radiosity, to about 40-secs per frame.

So I leave my Pc rendering happily, and when I come back after a bit, the frames are now taking 720-secs (12min) a frame?!

But if I cancel the render, and start where I left off, back It returns to 40-secs a frame. It's as if the frames get harder and harder to render as time goes by?!

Didn't have this prob with LW6, but now I'm using LW7.5b.

Have radiosity, shadowmaps etc cached.... please help this poor student before his deadline!!! :rolleyes:



05-04-2003, 08:24 AM
Hm i've heard about this problem with cached radiosity before, would also like to know why that happens (haven't rendered a longer animation myself yet but may need to in the next time)

Maybe Screamernet doesn't have that problem?

05-04-2003, 08:39 AM
It happens for me with the aa passes on still frames too. A few weeks ago I left the old girl going overnight on medium aa for a single still render. The first aa pass took 30 mins so I thought hey it'll finish in plenty of time by the time I get up. Nah, 8 hours later it's only on pass 5 of 9.

05-05-2003, 02:33 AM
Also, remember, even though LW is rendering an animation, it still has to render each frame as exactly that, a single frame.
Not every frame being rendered will have exactly the same properties, eg, an object being rendered at a distance will render faster than the same object close up.
In you animation, what going on?.
Render out single frame at frame, (were it seems to be taking longer than you expect) and you'll probably find the render times match whats happening with the animation.:)

05-05-2003, 07:27 AM
Thanks Mix!

Thing is, I tried that... there's really very little going on in the animation really, just a smooth camera pan and some robotic arms doing their thing!

Once the render times get chronic (12mins) I stop the animation. I then render the exact same frame that took the 12mins, and now it renders in like 40-seconds!

I've used Lightwave for a while now, and only since a recent upgrade to 7.5b have I noticed this strange phenominon.

It defys logic!!! :confused:

T x

05-05-2003, 11:10 AM
Well, diablo, I wouldn't say it defies logic. Perhaps they have tried to make the renderer a bit smarter and changed some code (on the road to v8) and it turned out that this was not so good an idea. Anyway, In other programs you have this behavior also. For instance in Maya caching everything can dramatically slow down things. I think the problem is, that caching not always works so well, cause there are some minor variations from frame to frame and the application wastes time analysing this state. In combination with a somewhat stupid memory management (acumulate cached states without flushing old ones) this can keep the program very busy. The worst case is when it actually starts swapping to disc. You know how this can ruin the day (and your render times).