View Full Version : render output is jumpy

07-10-2003, 08:24 PM
hey guys, i use lw 7.5 and when i render a scene containing motion it comes out looking jumpy and not very fluid at all. This jumpyness almost looks like a memory problem, like my machine is bogged down while viewing the quicktime file, but that is not the case. I usually render the scene out as a Quicktime file under MPEG-4 compression but i have tried many other settings and always get the same inconsistent, jumpy output.I have heard that for users without a Video toaster (like me) the best way to save an animation is by saving as an RGB and loading it into Premier or FCP, will this produce smoother more fluid animations?
anyone know what is causing this problem?
i am working on a shot now so i would hate to have it look like this:( thanks for the help guys!

07-10-2003, 09:10 PM
It's pretty hard to tell what the problem might be from the information you give.

It may not even be Lightwave related... it might be that your computer isn't fast enough to play back a Quicktime smoothly. What computer and OS do you have? What frame rate are you rendering to?

If you want to render to image sequences (which most people do), you don't necessarily have to buy an expensive editing or compositing package. Quicktime Pro (purchased from Apple's website) can load up all the image frames and translate them into a Quicktime.

07-10-2003, 10:33 PM
thanks for the quick reply, i dont think that RAM is the culprit although it does look like it should be because it will play for a while and then hit a snag and skip 20 or 30 frames and then keep going, and continue on like that. i use the latest version of osx on an ibook 384 megs of ram and 700 mh processor. Other larger QT movies will play with out a problem, just the ones i render with lw have this quirky, jumpy problem. I rendered my scene with just wireframes to see if that changes anything, but it still has the same problem. I will try and save using RGB and load that into Premier or QT pro as you said. If you have any other ideas id love to hear it, Hopfully it helps! thanks for the advice

07-10-2003, 10:36 PM
30 fps NTSC, btw

07-11-2003, 01:36 AM
That's really strange...

Just to eliminate the playback problem possibility, try rendering to a really small resolution like 320x240 or 160x120 - also try doing a preview in the camera viewport to compare.

07-11-2003, 07:28 AM
I still think it's most likely the computer is not fast enough to play back the Quicktime. The more data the Quicktime has, the more it'll be a strain on the hard drive. Smaller, compresssed Quicktimes usually playback better than larger uncompressed ones.

On Quicktime Pro there is a feature on the menu called "play all frames". When this is activated it'll slow down the playback speed of the Quicktime (and play all frames) rather than jumping frames to catch up.

On any QT player, load up your jumpy movie and move forward frame by frame (by hitting the arrow key) and you'll be able to see whether the "jumps" are actually on the Quicktime, or whether it's just skipping them on playback.

07-12-2003, 07:34 PM
Like he said though, he usually uses MPEG-4 compression, and other settings haven't worked either. And it doesn't look like his computer isn't fast enough.

I don't really know what the problem could be, but i have a thought. heaveninarms, when you render from LW do you leave the keyframe option checked in the quicktime options? Alot of times this is automatically checked, and set to keyframe every frame. I don't know what keyframes in a quicktime movie are, but i know they are not needed, and i believe that they do add data to movie, potentially making the data rate to high to handle.

07-12-2003, 08:20 PM
a keyframe in QT is how often a full-frame image is saved in the file, instead of just what's changed from the last frame. 1 keyframe per frame I believe is the same as no keyframes. With a key every 30 frames, it will not save an entire image until the 30th frame, only what data has changed from frame to frame - which makes the filesize smaller at the expense of quality - I don't think it ever makes the data rate higher -

07-13-2003, 11:36 AM
alright thanks for all the suggestions, i think whats causing the problem is that the data rate per second is too high and strains the processor on playback. on the jumpy animation i looked at the "get movie properties" option on QT pro and found out that the movie is trying to process up to 30 mb a second while regular movies that have no problem are playing at under 300k a second. so iv been messing around with the "limit data rate to..." setting in the options panel of render options and have been getting better results, does anyone else have to adjust the "limit data rate" option before rendering?