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View Full Version : Bouncing ball animation... learning from scratch


denil
11-10-2008, 03:13 PM
This is my 1st attempt to learn animation the correct way ie by animating the bouncing ball... Once i get this right, then i'm guessing the next step would be to animate a heavier ball... all critiques are welcomed... thanks

http://www.vimeo.com/2204485

robcat2075
11-10-2008, 06:50 PM
I think the bouncing motion is pretty good (except for the very last bounce, which always seems to be the hardest to make look right)

I sort of want the ball to roll more in response the to ground contact, but the bouncing like it's working well.

denil
11-11-2008, 05:56 PM
Thanks rob... i did what u asked and made the ball sort of roll to a stop...

interestingly i came across this that maya's playback is way faster than the actual speed its supposed to play which i came to know a little too late i guess... what plays in 4 sec in maya was actually around 7-8 seconds at 24 fps which is why after rendering it out from premiere, its pretty slow as compared to how i thought it actually was... will try and redo the timing and fix it...

again all critiques welcomed :cool::D


http://www.vimeo.com/2215642

robcat2075
11-11-2008, 07:57 PM
There is a preference setting in Maya that will make it try to maintain your intended frame rate rather than race thru as fast as it can. Ask on the Maya subforum and I bet some smartypants will tell you exactly where that is.


the roll to a stop looks better in attempt #2 but something has changed about the bouncing motion. it's not quite impacting the ground like it did in attempt #1. It almost appears to be hanging from a spring rather than "bouncing". I suspect the ball is slowing down a bit as it nears the ground (bouncing balls don't do that) but not possible to analyze that on the non-scrubbable vimeo video.

denil
11-12-2008, 05:50 PM
found out why there was a difference... my playback was set to play every frame instead of 24fps

well i made some more changes... hopefully this corrects what errors i did in the previous one... however got some other weird problem while rendering out a quicktime file... for some reason adobe premiere has skipped some frames and i can't seem to understand why... again will be doing some research on why that's happening, but till then just ignore those strange pops that happen... otherwise how does it look?


http://www.vimeo.com/2225136

Thanks!!

robcat2075
11-12-2008, 09:35 PM
My first guess is that the missing frame are because the frame rate of your render and the frame rate of your after effects project are not the same.

Sometimes AE will import footage and assign the wrong fps to it.

The bounce still looks weird to me.

denil
11-13-2008, 07:36 AM
does it look weird coz the bounces are too close and not spaced out??

lifeofillusion
11-13-2008, 02:17 PM
is the video missing some frames...DENIL will it be possible for u too post the mov file somewhere and share the link here?

denil
11-13-2008, 03:04 PM
yup it does skip some frames... for some reason if i render out at 24fps it skips some frames... so rendered it out at 25fps n it came out fine... here's a link to download the mov file...

http://cid-87465c44a71b2eb7.skydrive.live.com/self.aspx/Public/bouncingBall1.mov

i hope it can be downloaded... 1st time trying out skydrive

Thanks!!

robcat2075
11-14-2008, 03:50 AM
i hope it can be downloaded... 1st time trying out skydrive

Thanks!!

no go here. only 21Kb downloads and I get the message "not a movie file".

Maybe got corrupted.

denil
11-17-2008, 06:40 AM
sorry for a late reply... i asked some of my friends to try and download it and they could... could u try and check again if u can...

i'll be posting a new animation soon, had been tied up with work and some other things... update soon :)

robcat2075
11-18-2008, 02:45 AM
ok, got it.

I stepped thru it and counted frames and here's what I think was bugging me... gravity doesn't seem to be pulling on the ball with the same force after each bounce.

To quanitfy this a bit, I counted the frames it took for the ball to drop from the peak of each arc to the ground and came up with these

6 6 5 5 5 5 4 4 3 3 3 3 2 1


So we have quite a few drops that are taking the exact same length of time to happen.

For example drops 3, 4, 5, and 6 all take 5 frames to hit the ground.

Even though they are all falling from different distances, they are taking the same amount of time, which is impossible.

If you dropped a ball from 3 feet and again from 1 foot you wouldn't expect the second one to take as long to hit the ground as the first. And it wouldn't, because gravity doesn't pull any less from 1 foot above the ground than it does from 3.

Put another way the second drop should take the same amount of time to fall from 1 foot to 0 feet as the first drop did to fall from 3 feet to 2 feet. The acceleration of gravity is "constant" meaning objects gain speed at the same rate.

Looking back at the animation, drop 6 is falling from 1/3 the height that drop 3 falls from yet takes the same amount of time. And even though succeeding bounces shave some frames off, they never shave off enough, so by the end, the ball ends up spending impossibly long amounts of time in the air for bounces that aren't nearly high enough to account for that time.

What to change? If I had to have that many bounces I might each successive bounce decay much less so the height of similar bounces wouldn' t be so different. Or I'd drop it from a lot higher so there would be more time to whittle from on each bounce.

On another note, there are several brief stretches around the bounces where the ball is moving rather linearly, rather than accelerating or decelerating. It's brief, but it's enough undo that feeling of gravity in spots.

denil
11-18-2008, 12:17 PM
ahh i see rob... i'll def look into that and fix it, physics was my weaker subjects :)... sadly my graphics card blew up on me yesterday so an update will take sometime till i get a new card... but thanks a lot for all the pointers and checking out the file... will def work on improving it now that i know what i was doing wrong :)

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