Hi folks. Another day's work, another animation...

Actually, this is a fast one (12 mins to render - 8 when I only used 1 might
source!) It's a (hopefully) physically-correct bounding ball. Let me know
what you think!

http://www.btinternet.com/~orphi/Video/Kinetics1.m1v

It's roughly 1.5MB, 250 frame @ 25 fps = 10 seconds. Hope you like it ;-)

Notice how towards the very end the bouncing goes wrong... It's due to the
way the bounce detection macro works... A real ball would eventually just
roll along the ground, but mine keeps randomly bouncing. Theoritically if
you did it at a high enough frame rate (say, 1,000,000 fps) this would go
away - but there *has* to be a better way!

Anyway, my next project is the Chaos Penulum ;-)
Andrew.

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On Fri, 27 Sep 2002 17:12:50 +0100, "Andrew Coppin"
<orp### [at] btinternetcom> wrote:

>Actually, this is a fast one (12 mins to render - 8 when I only used 1 might
>source!) 

In my state of mind and body, I could definitely use a might source.
Any free ones?

<follow-ups set>


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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> Notice how towards the very end the bouncing goes wrong... It's due to the
> way the bounce detection macro works... A real ball would eventually just
> roll along the ground, but mine keeps randomly bouncing. Theoritically if
> you did it at a high enough frame rate (say, 1,000,000 fps) this would go
> away - but there *has* to be a better way!


I think it would look more realistic if it didn't bounce as high each time.
If each time it bounces 50% or so of the amount it bounced the last time, it
would approach a roll sooner.

 - Slime
[ http://www.slimeland.com/ ]

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Andrew Coppin wrote:
> 
> Hi folks. Another day's work, another animation...
> 
> Actually, this is a fast one (12 mins to render - 8 when I only used 1 might
> source!) It's a (hopefully) physically-correct bounding ball. Let me know
> what you think!
> 
> http://www.btinternet.com/~orphi/Video/Kinetics1.m1v
> 

I wasn't able to view it, it seems to be marked as a text file on your
webserver.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______

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As I say, it's all in the bounce. I've been fiddling with the height ratio
for ages... Too low and the ball bounces once and it's over. Too high and
the ball actually bounces *heigher* each time! 8-0 And as I said, when the
ball stops bouncing, the macro kinda goes wrong (it only calculates one
bounce per frame, and starts being a bit random... maybe I need to put in an
artificial smoothing term or something...)

The acceleration of the ball should be exactly 8.9006m/s^2 (if the animation
actually plays back at 25fps, and you assume the ball is 1 meter across).
The bouncing part probably isn't very realistically simulated - to be
honest, I don't know much about the physics of bouncing!

Anyway, tomorrow I'm going to attack the Chaos Pendulum. That doesn't
involve any bouncing, only the interplay of forces and Newton's laws of
motion, so I should be able to get it down fairly well!

Until tomorrow...
Andrew.

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"Andrew Coppin" <orp### [at] btinternetcom> wrote in
news:3d94b015@news.povray.org: 

> As I say, it's all in the bounce. I've been fiddling with the height
> ratio for ages... Too low and the ball bounces once and it's over. Too
> high and the ball actually bounces *heigher* each time! 8-0 And as I
> said, when the ball stops bouncing, the macro kinda goes wrong (it only
> calculates one bounce per frame, and starts being a bit random... maybe
> I need to put in an artificial smoothing term or something...)
> 
> The acceleration of the ball should be exactly 8.9006m/s^2 (if the
> animation actually plays back at 25fps, and you assume the ball is 1
> meter across). The bouncing part probably isn't very realistically
> simulated - to be honest, I don't know much about the physics of
> bouncing! 

Your ball is a bit too rigid, you should scale it slightly when it touches 
the ground... Squash and stretch are the basis of good animation (cartoon 
ones, at least :-)

Just to complicate a bit your macros :-P

-- 
--=#=--=#=--=#=--=#=--=#=--=#=--=#=--=#=--=#=--
Philippe Lhoste (Paris -- France)
Professional programmer and amateur artist
http://jove.prohosting.com/~philho/

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