#1 11-29-2010 1:54 pm

Erik
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Speed of bouncing ball

Hi! I'm doing a bouncing ball exercise. And I got some basic questions that I hope someone can answer.

For example a tennis ball.
If the second bounce reaches half height of the first bounce, will that bounce take half the time?

Will the rotation of the ball accelerate when it bounces? Will it keep spinning in the same direction if it bounces against a wall?

What is the basic rules of making it look heavier or lighter?

Any kind of help is appreciated!

/Erik

Last edited by Erik (11-29-2010 6:16 pm)

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#2 11-29-2010 2:31 pm

Martyn
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Re: Speed of bouncing ball

Hey Erik, this video should help...

Direct Link


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#3 11-29-2010 3:51 pm

varma.pericharla
From: hyderabad
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Re: Speed of bouncing ball

as u said for the second bounce the ball raise only half distance than the first . so not only the bounce the distance traveled also  decreases
                   so if u reduce the time by half it wont work because for first bounce if it takes 12 frames and for second u give only 6 frames  than    the action happens more quicker as your reducing the height and distance also . which will not work out. u cant reduce by half the time u can just reduce by 2 to 3 frames ,

Last edited by varma.pericharla (11-29-2010 3:51 pm)

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#4 11-29-2010 4:26 pm

cosmicfool
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Re: Speed of bouncing ball

the rules are always different Erik. Some tennis balls are more worn than other tennis balls. They have more compression than others, more felt etc.....
Shoot your reference, or look at some stuff on youtube, and check out the timing and the peaks of each bounce, and bam you have your answer. Or go out and look at animation books that have countless bouncing ball tutorials that you can use to learn from.
Here's a link of a photo with the timing and the spacing of one explained.
http://i130.photobucket.com/albums/p264 … xample.jpg


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#5 11-29-2010 4:32 pm

martie
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Re: Speed of bouncing ball

Would you not increase the frames it took for the second and third bounce.    You would not reduce the frames right?   so the first bounce would be the bounce with the most energy so the bounce would be faster so less frames, the second bounce wold be less energy so more frames it would take right? beacuse it is moving slower.  So from droping the ball  that would be the fastest as it has the most energy, so this would be the least amount of frames, and second probably a few frames more than the initial drop, the third bounce would require a few frames more than the second am I correct?.  Obviuosly you would work on the timing and spacing to try get it to look proper.

Last edited by martie (11-29-2010 4:33 pm)


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#6 11-29-2010 6:08 pm

cosmicfool
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Re: Speed of bouncing ball

martie wrote:

Would you not increase the frames it took for the second and third bounce.    You would not reduce the frames right?   so the first bounce would be the bounce with the most energy so the bounce would be faster so less frames, the second bounce wold be less energy so more frames it would take right? beacuse it is moving slower.  So from droping the ball  that would be the fastest as it has the most energy, so this would be the least amount of frames, and second probably a few frames more than the initial drop, the third bounce would require a few frames more than the second am I correct?.  Obviuosly you would work on the timing and spacing to try get it to look proper.

Nope, your wrong.
As the ball keeps moving it loses momentum. Each bounce using less force = less rise time, less hang time, less drop time = less time = less frames.


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#7 11-29-2010 7:22 pm

Erik
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Re: Speed of bouncing ball

Thank you all for your comments!

Do anyone have some good reference videos that I can step frame by frame in?

I have watched some references and played around with a tennis-ball at home, and all I get is, "hmm maybe its like this" and " Seems like this is what happens"

So I thought i could ask you guys, I want to be sure of things smile

I want to learn how it works, so i don't have to watch references all the time for something as basic as a bouncing ball.

But maybe I am thinking about this the wrong way, maybe its also an exercise in understanding how things work just by looking at it.

Maybe its best to try to learn this "basic" things all by my self. I guess I must change my focus from" making a great bouncing ball animation as fast as possible" to "try to learn as much as possible from this exercise."

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#8 11-29-2010 8:34 pm

aja
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Re: Speed of bouncing ball

Erik wrote:

...maybe its also an exercise in understanding how things work just by looking at it.

Yes, exactly!  You can figure out how to animate a bouncing ball mathematically, that's why physics simulators in Maya do a good job with things like bouncing balls, but to animate it based on calculations would miss the point of the exercise.  The most valuable skill you need to develop as an animator is the ability to see if a particular movement/performance looks "right", and that takes lots and lots of practice.  It's why so much student work is "floaty", because the student animators can't tell that what they're doing doesn't look right.  Try animating the ball, then compare it to a real ball bounce and see if yours looks similarly heavy/snappy/realistic.  Post it for feedback to see what other people think, then try to make it look better.  Etc etc.

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#9 11-30-2010 2:33 am

cosmicfool
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Re: Speed of bouncing ball

Agreed completely. When learning it isn't about making a ball bounce as quickly as possible. Its about understanding the principles and how to make it bounce. Then once you understand it, try to make as many as possible as fast as possible so you pound all of that info into your brain. Eventually you will be able to bounce a ball in maya in seconds just by using the graph editor, and giving it whatever feeling you want it to have. Why not do a couple and post the results in here just as Aja said. Most people are more than happy to help a new comer out. If you have any software issues fire them in here as well, that is half the battle with doing your first exercise.


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#10 11-30-2010 4:06 am

eric s
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Re: Speed of bouncing ball

Hi Erik,

You've garnered some pretty great advice in this thread.  smile   I'd just like to throw in one more suggestion.

Your original posted had some questions about how much a ball will rotate based on its speed, number of bounces, etc.   I would recommend that, just for now, you don't worry about rotation at all.

I think it's great that you've dedicated yourself to starting off with a ball bounce.   It's a great way to learn about timing and spacing.   Rotating the ball will likely get in the way off all that you'll be observing and learning.  So, for now, I'd recommend making your CG ball just one flat color and pay attention to where it is in the frame.   If it's just one color you can imagine that it's rotating the proper amount, and you'll be concentrating on what's really important: the timing and spacing.

Good luck, and I look forward to seeing your progress!

- Eric


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#11 12-01-2010 3:46 am

robcat2075
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Re: Speed of bouncing ball

Just a note about gravity... gravity is an accelerating force.  A ball that falls from 2 feet doesn't take 2x as long as a ball that falls from 1 foot. 

But don't feel bad if you didn't know that instinctively, it took about 10 thousand years of human civilization watching things fall before anyone noticed.



aja wrote:

It's why so much student work is "floaty", because the student animators can't tell that what they're doing doesn't look right.

Animation is like beer goggles, it has a way of making things seem better than they really are.

Last edited by robcat2075 (12-01-2010 3:49 am)


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#12 12-05-2010 5:39 pm

Erik
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Re: Speed of bouncing ball

Thank you very much for the encouragement and advice! I haven't had much time to animate until today.

robcat2075 wrote:

But don't feel bad if you didn't know that instinctively, it took about 10 thousand years of human civilization watching things fall before anyone noticed.

Hehe yes, I guess somethings are only noticed when they are missing. It seems easy to feel that something is wrong, but really hard to see what it is that is wrong.

This is my latest version of  a bouncing tennis-ball.

Direct Link


http://dl.dropbox.com/u/15068346/graph.PNG

Should I post a new thread in the "Personal Work and Demo Reels" forum instead of posting my videos in this thread?

/Erik

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#13 12-05-2010 10:33 pm

robcat2075
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Re: Speed of bouncing ball

To my eye, the first fall seem off. For frames 5,6,7,8 the ball falls on a constant slope rather than accelerating.

the next few may have a bit of this problem but have less time for it to become apparent.

Learning to recognize a true parabola is a good skill for bouncing ball since all ballistic object move on parabolas and never on steady slope.

But that's not a *bad* bouncing ball.


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#14 12-06-2010 2:29 pm

Erik
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Re: Speed of bouncing ball

Ah! Thank you!

I think that I'm going to try to animate balls with different weight now. There seems to be no basic rule how to make the ball look heavier in general. They fall at the same speed, and could have the same bounciness (depending on the material of the floor and ball). I think they will not roll/spin as much as a light ball, but as "eric s" said, I think its better to not worry about rotation before i learn timing and spacing.

Maybe most people is showing it on a standard, not so hard floor, because then I think a heavy ball would not bounce as much as the light one.

Hmm it still feels like I'm forgetting something...

/Erik

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#15 12-06-2010 2:49 pm

Erik
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Re: Speed of bouncing ball

Hi Oro! Yes that is how i do it too.

/Erik

Last edited by Erik (12-06-2010 2:49 pm)

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#16 12-07-2010 4:48 am

alonso
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Re: Speed of bouncing ball

http://brendanbody.blogspot.com/2009/06 … again.html

this dude has some good bouncing ball tutorials, with some a few new thoughts for old animators too wink

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#17 12-07-2010 8:26 pm

cosmicfool
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Re: Speed of bouncing ball

hey Erik, it's coming better. I think you need to address your inbetween or break down keys a little better on the up and down action. I whipped up a really quick bounce using the same timing as you did. I won't post a playblast of it, but here is the graph editor. Notice how my breakdown keys are in much more control of the movement of the ball, and really affect the arc of the curves. They affect the rise the fall and the hangtime significantly on each bounce. Also notice how in the first 4 bounces the arcs of each curve looks pretty similar, and it has a consistent feel, just less energy. Hope that helps you out a bit.

http://i123.photobucket.com/albums/o320/pawnfondler/ballbounce.jpg

Last edited by cosmicfool (12-07-2010 8:27 pm)


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#18 12-16-2010 10:27 pm

Erik
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Re: Speed of bouncing ball

Thank you all for your help!
Could some moderator move this thread to the "Personal Work and Demo Reels" forum? Or could I do that my self somehow?

I'm sorry for taking so much time between my posts, but this time its not my fault smile My AC adapter in my computer got overheated and died, so I had to buy a new one.

What do you think about this two bounces? The right is the bounce from my earlier post, I tried to make it better.
The left one is a heavier/less bouncy ball. The heavy reference ball is actually lighter than the tennis-ball, but less bouncy so I think it looks heavier. How can someone show that something is light but not bouncy? Or heavy and bouncy?

Does the left ball look heavier or just less bouncy?

Direct Link

Last edited by Erik (12-17-2010 10:25 pm)

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#19 11-29-2011 2:37 pm

robcat2075
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Re: Speed of bouncing ball

I think those are both plausible bouncing balls.  I think you have also discovered that the way most animators (even animation teachers) talk about "light" and "heavy" bouncing balls is seriously out of whack.  "Light" rarely equals ""bouncy" in real life.

Erik wrote:

How can someone show that something is light but not bouncy? Or heavy and bouncy?

To go beyond abstract tests like these I think you need context for your animation.  Balloons and soap bubbles are very light (air resistance prevents them from even falling normally) balls but hardly bounce at all. Model your ball to resemble one of those, animate it properly and your audience will connect the dots.

Erik wrote:

Does the left ball look heavier or just less bouncy?

They both look appropriately massive.  To make a VERY light ball you'll need to show air resistance being a visible factor in the ball's movement. Truly light balls don't bounce much.

I did a light ball/heavy ball test where I tried to take it to the most absurd extreme I could think of:

http://2dwannabe.blogspot.com/2009/01/r … lloon.html

But I wouldn't worry about this too much.  You've demonstrated you can bounce a ball and can show different amounts of decay.  Move on to the next problem, a ball bouncing on obstacles.


"3D animators have pencil envy" - Robert Holmén
The world's most beloved Heavy Push
This is only a... my gallery of CG tests
I'm a 2D Wannabe...  drawings and 2D animation tests

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#20 11-29-2011 11:38 pm

Crayon10
Registered: 11-20-2010
Posts: 142

Re: Speed of bouncing ball

robcat2075 wrote:

I did a light ball/heavy ball test where I tried to take it to the most absurd extreme I could think of:

http://2dwannabe.blogspot.com/2009/01/r … lloon.html

But I wouldn't worry about this too much.  You've demonstrated you can bounce a ball and can show different amounts of decay.  Move on to the next problem, a ball bouncing on obstacles.

Excellent clip of a bounce.

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#21 12-30-2012 4:40 am

turtle
Registered: 12-24-2012
Posts: 86

Re: Speed of bouncing ball

hey this is great info , ive been working on ball bounce exercise feeling kinda dumb for spending so much time on it and it always doesnt look perfect haha but i have been learning how to understand timing and spacing better.

learning how to use tangents to do what you want is kinda hard. any good tangent manipulating guides?

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#22 12-30-2012 4:54 am

robcat2075
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Re: Speed of bouncing ball

turtle wrote:

learning how to use tangents to do what you want is kinda hard. any good tangent manipulating guides?

I'll note that if something is not in the right place at the right time, you don't HAVE to edit curves to get it there, you can keyframe it to be  in the right place at the right time even to the point of keyframing it on every frame if need be.  But then go look at the curves that made and you may say  "ah, I could have gotten those same shapes with just a few keys if I had changed the slope to do this instead of that..." And then you'll know better next time.


"3D animators have pencil envy" - Robert Holmén
The world's most beloved Heavy Push
This is only a... my gallery of CG tests
I'm a 2D Wannabe...  drawings and 2D animation tests

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