POV-Ray : Newsgroups : povray.advanced-users : Locus of a moving point? Server Time: 9 Dec 2018 21:35:01 GMT
 Locus of a moving point? (Message 1 to 8 of 8)
 From: Mike Horvath Subject: Locus of a moving point? Date: 12 Sep 2018 21:58:41 Message: <5b998c11\$1@news.povray.org>
```I am thinking of creating a model of the solar system in POV-Ray.
However, one of the things I would like to do is trace the path (locus)
of each planet around the sun so that the distance traveled so far is
visible. How would I accomplish this in POV-Ray? Thanks.

Mike
```
 From: Kenneth Subject: Re: Locus of a moving point? Date: 13 Sep 2018 19:25:00 Message:
```Mike Horvath <mik### [at] gmailcom> wrote:
> I am thinking of creating a model of the solar system in POV-Ray.
> However, one of the things I would like to do is trace the path (locus)
> of each planet around the sun so that the distance traveled so far is
> visible. How would I accomplish this in POV-Ray? Thanks.
>

As a purely visable trail that builds up as a planet moves? Or as a numerical
distance? The former is something I've done before, although I no longer have
the code. (I used closly-packed spheres to trace the trajectory, adding more
spheres during an animation). But I don't remember if I did it all within the
scene code, or if had to resort to #write/#read to another file, to recall all
the previous positions.
```
 From: Kenneth Subject: Re: Locus of a moving point? Date: 13 Sep 2018 19:35:01 Message:
```"Kenneth" <kdw### [at] gmailcom> wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
> > I am thinking of creating a model of the solar system in POV-Ray.
> > However, one of the things I would like to do is trace the path (locus)
> > of each planet around the sun so that the distance traveled so far is
> > visible. How would I accomplish this in POV-Ray? Thanks.
> >
>
> As a purely visable trail that builds up as a planet moves? Or as a numerical
> distance? The former is something I've done before...

Actually, it might be a simple procedure (but it's only my thought experiment,
beware!) The planet needs some starting position; then use a #while or #for loop
to advance that position incrementally, adding a small sphere there each time.
At the end of the loop, add your planet object. There should be a visible trail
of spheres as the trajectory. I think!
```
 From: Bald Eagle Subject: Re: Locus of a moving point? Date: 13 Sep 2018 23:40:01 Message:
```Mike Horvath <mik### [at] gmailcom> wrote:
> I am thinking of creating a model of the solar system in POV-Ray.
> However, one of the things I would like to do is trace the path (locus)
> of each planet around the sun so that the distance traveled so far is
> visible. How would I accomplish this in POV-Ray? Thanks.
>
>
> Mike

You should be able to peg that to whatever you're using to determine the
position of the planet in the animation.

So just use a torus, or section of scaled torus, or an elliptical sphere sweep
that starts at zero, and goes to wherever your planet currently is.

I managed to use a Dupin cyclide - but nevermind me.

Have you managed to determine how all the planets are aligned at some initial
starting point?
```
 From: Mike Horvath Subject: Re: Locus of a moving point? Date: 13 Sep 2018 23:45:49 Message: <5b9af6ad\$1@news.povray.org>
```On 9/13/2018 7:36 PM, Bald Eagle wrote:
> Have you managed to determine how all the planets are aligned at some initial
> starting point?
>
>

Here's what I've done so far.

https://www.geogebra.org/m/prtwmh2d

It's two-dimensional, but I have calculated the coordinates for the
third dimension as well.

I think I can sample points along the orbits and connect them with
lines. Or create a parametric object that uses the same formulas. It
will take some work however.

Mike
```
 From: Mike Horvath Subject: Re: Locus of a moving point? Date: 13 Sep 2018 23:46:43 Message: <5b9af6e3\$1@news.povray.org>
```On 9/13/2018 3:31 PM, Kenneth wrote:
> Actually, it might be a simple procedure (but it's only my thought experiment,
> beware!) The planet needs some starting position; then use a #while or #for loop
> to advance that position incrementally, adding a small sphere there each time.
> At the end of the loop, add your planet object. There should be a visible trail
> of spheres as the trajectory. I think!
>
>
>

I have done this very thing in 2D, but it does not look nice or smooth.

Thanks.

Mike
```
 From: Alain Subject: Re: Locus of a moving point? Date: 14 Sep 2018 00:23:23 Message: <5b9aff7b@news.povray.org>
```Le 18-09-13 Ã  19:46, Mike Horvath a Ã©critÂ :
> On 9/13/2018 3:31 PM, Kenneth wrote:
>> Actually, it might be a simple procedure (but it's only my thought
>> experiment,
>> beware!) The planet needs some starting position; then use a #while or
>> #for loop
>> each time.
>> At the end of the loop, add your planet object. There should be a
>> visible trail
>> of spheres as the trajectory. I think!
>>
>>
>>
>
> I have done this very thing in 2D, but it does not look nice or smooth.
>
> Thanks.
>
> Mike
Then, use a sphere_sweep using every 10th sphere.
```
 From: Mike Horvath Subject: Re: Locus of a moving point? Date: 14 Sep 2018 07:06:35 Message: <5b9b5dfb\$1@news.povray.org>
```On 9/13/2018 8:24 PM, Alain wrote:
> Le 18-09-13 Ã  19:46, Mike Horvath a Ã©critÂ :
>> On 9/13/2018 3:31 PM, Kenneth wrote:
>>> Actually, it might be a simple procedure (but it's only my thought
>>> experiment,
>>> beware!) The planet needs some starting position; then use a #while
>>> or #for loop
>>> each time.
>>> At the end of the loop, add your planet object. There should be a
>>> visible trail
>>> of spheres as the trajectory. I think!
>>>
>>>
>>>
>>
>> I have done this very thing in 2D, but it does not look nice or smooth.
>>
>> Thanks.
>>
>> Mike
> Then, use a sphere_sweep using every 10th sphere.

This does seem to be the best (and easiest) solution unless I want to
wait many hours for the parametric objects to render. (I am creating an
animation.)

Mike
```