POV-Ray : Newsgroups : povray.binaries.animations : Gravity Comparison Server Time: 16 Dec 2018 00:48:08 GMT
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From: Jörg "Yadgar" Bleimann
Subject: Gravity Comparison
Date: 9 May 2017 22:35:51
Message: <59124447@news.povray.org>
Hi(gh)!

Having started venturing into the realm of physical simulation for the 
very first time (I just want to get a believable marble lane animation 
running... without having to learn Blender and Blender Game Engine at 
first!), here is a first small animation dealing with gravity on various 
celestial bodies, even small enough to be posted here.

The fall height of all balls is 30 metres, time is real-time (so don't 
wonder about the leftmost ball :-)).

See you in Khyberspace!

Yadgar


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Attachments:
Download 'gravity.mp4.mpg' (1542 KB)

From: Stephen
Subject: Re: Gravity Comparison
Date: 9 May 2017 22:51:24
Message: <591247ec$1@news.povray.org>
On 5/9/2017 11:35 PM, Jörg "Yadgar" Bleimann wrote:
> Hi(gh)!
>
> Having started venturing into the realm of physical simulation for the
> very first time (I just want to get a believable marble lane animation
> running... without having to learn Blender and Blender Game Engine at
> first!), here is a first small animation dealing with gravity on various
> celestial bodies, even small enough to be posted here.
>
> The fall height of all balls is 30 metres, time is real-time (so don't
> wonder about the leftmost ball :-)).
>
> See you in Khyberspace!
>
> Yadgar


Nice and I like your stage.
Next, they need to bounce. :)

-- 

Regards
     Stephen


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From: clipka
Subject: Re: Gravity Comparison
Date: 10 May 2017 13:54:50
Message: <59131baa$1@news.povray.org>
On my machine, I just see pitch black.


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From: Stephen
Subject: Re: Gravity Comparison
Date: 10 May 2017 14:51:22
Message: <591328ea$1@news.povray.org>
On 5/10/2017 2:54 PM, clipka wrote:
> On my machine, I just see pitch black.
>

I get that when I open it with quick time. It plays fine on MPC-HC.

-- 

Regards
     Stephen


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From: omniverse
Subject: Re: Gravity Comparison
Date: 10 May 2017 21:20:01
Message: <web.591382d3f6e11aaf9c5d6c810@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> On my machine, I just see pitch black.

Same here. Win10 Movies & TV player, or WMP which also freezes and must "end
task" on that.


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From: dick balaska
Subject: Re: Gravity Comparison
Date: 10 May 2017 23:59:23
Message: <5913a95b$1@news.povray.org>
Am 2017-05-10 17:14, also sprach omniverse:
> clipka <ano### [at] anonymousorg> wrote:
>> On my machine, I just see pitch black.
>
> Same here. Win10 Movies & TV player, or WMP which also freezes and must "end
> task" on that.
>

My Win 8.1 vlc plays fine.
The video is a bit off-size. Windows explorer reports a frame size of 
16x160. But
$ ffprobe Gravity.mp4
Stream #0:0(und): Video: h264 (High 4:4:4 Predictive) (avc1 / 
0x31637661), yuv444p, 1080x720, 794 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 
tbc (default)

1080x720 is pretty close to what I see it as.
-- 
dik


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From: Kenneth
Subject: Re: Gravity Comparison
Date: 11 May 2017 14:30:00
Message: <web.591473e2f6e11aaf883fb31c0@news.povray.org>
My Windows 7's  default "Windows Media Player" doesn't play it, but it plays
fine in SMplayer (the GUI version of Mplayer.)

Yes, now it's time to add some bouncing. I haven't done that yet with any of my
own animations, but it would *seem* to be not-too-difficult. I guess the
simplest idea would be to use the same gravity-accelleration code you already
have, then reverse(?) it for the upward part of the bounce--then cycle those two
motions, with maybe just a decreasing height each time. (Of course, this dosn't
take into account any actual object 'collision' physics, but it should look nice
anyway.)

This is just a 'thought experiment', so no results are guaranteed ;-)
(That's my legal disclaimer, ha!)


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From: Bald Eagle
Subject: Re: Gravity Comparison
Date: 11 May 2017 17:15:01
Message: <web.59149c0af6e11aafc437ac910@news.povray.org>
"Kenneth" <kdw### [at] gmailcom> wrote:

had the same idea when I was working on a bouncing ball animation,  but you
really only need one equation to plug the clock into.

http://feucht.us/writings/bouncing_ball.php

I never got it to work out quite the way I wanted, but all of the up and down
motion is in one equation.


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From: Stephen
Subject: Re: Gravity Comparison
Date: 11 May 2017 18:21:56
Message: <5914abc4$1@news.povray.org>
On 5/11/2017 6:14 PM, Bald Eagle wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>
> had the same idea when I was working on a bouncing ball animation,  but you
> really only need one equation to plug the clock into.
>
> http://feucht.us/writings/bouncing_ball.php
>
> I never got it to work out quite the way I wanted, but all of the up and down
> motion is in one equation.
>
>
>

I find that S = u*t + 0.5*a*t^2 works well enough for me. :)

As for the bounce, just reverse the velocity when the ball is less than 
its radius  from the floor. Then reduce it by a damping factor.

-- 

Regards
     Stephen


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From: Kenneth
Subject: Re: Gravity Comparison
Date: 12 May 2017 00:15:01
Message: <web.5914fe20f6e11aaf883fb31c0@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>
> had the same idea when I was working on a bouncing ball animation,  but you
> really only need one equation to plug the clock into.
>
> http://feucht.us/writings/bouncing_ball.php
>

Very interesting. While reading that article, I kept thinking of Zeno's Paradox
(running a race but never getting to the finish line.) Then the author mentions
Zeno at the end, ha!


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