POV-Ray : Newsgroups : povray.text.scene-files : Planetarium Server Time
4 Feb 2023 20:40:01 EST (-0500)
  Planetarium (Message 7 to 16 of 16)  
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From: Bald Eagle
Subject: Re: Planetarium
Date: 14 Sep 2018 09:40:01
Message: <web.5b9bb965ebad83c3c437ac910@news.povray.org>
Mike Horvath <mik### [at] gmailcom> wrote:

> How do I split such a function into parts? For instance

It's already in parts.

What you can do is limit the range of U and V over which those functions are
evaluated.

If you limit U or V to the range from 0 to 0, then you will get a circle.
Swap U and V, and you get "the other" circle

Limit the ranges of both to a fraction of (2*pi), and you get a curved patch
that only covers part of the torus' surface.

Keep one full 2*pi range, and limit the other, and you get a "hoop sweep" around
the torus, one way or the other.

The set of macros takes this concept and just does it 4 times (0, +TStep,
+PStep, +both) to generate 4 corners, and fills that in with 2 smooth triangles.

See clipka's favorite link:
https://nylander.wordpress.com/2008/08/25/cross-section-of-the-quintic-calabi-yau-manifold/

There is no magic.

Look back through the forums, and you can see that we've been exploring this
basic concept --- for years.



#version version;

#include "colors.inc"

light_source {
 <5, 10, -20>
 color White
 fade_distance 20
 fade_power 2
}

camera {
    location  <0, 2, -35>
    look_at   <0, 0, -10>

    right x*image_width/image_height
    up y
}

#declare U1 = 0;   // small radius
#declare U2 = 2*pi;   //
#declare V1 = 0;   // large radius
#declare V2 = 2*pi;   //
#declare r0 = 10;
#declare r1 = 4;
#declare SphereRadius = 0.1;


// Create a set of points on the surface of a Torus
#declare X = function (T, P, R, r) {cos(T) * ( R + r * cos(P) )}
#declare Y = function (T, P, R, r) {-sin(T) * ( R + r * cos(P) )}
#declare Z = function (T, P, r, n) {r * sin(P)}

#declare TStep = 0.02;
#declare PStep = 0.05;

#for (Theta, U1, U2, TStep)
    #for (Phi, V1, V2, PStep)
        #local XYandZResultOfParametricFunctionsEvaluatedForThisImmediateUandV =
<X (Theta, Phi, r0, r1), Y (Theta, Phi, r0, r1), Z (Theta, Phi, r0, r1)>;
        sphere {XYandZResultOfParametricFunctionsEvaluatedForThisImmediateUandV
SphereRadius pigment {White}}
    #end
#end


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From: Mike Horvath
Subject: Re: Planetarium
Date: 15 Sep 2018 05:26:14
Message: <5b9cd036$1@news.povray.org>
On 9/13/2018 7:59 PM, Mike Horvath wrote:
> I have attached my scene file so far. It already calculates the 
> positions of the planets. However, I want to create parametric tori 
> showing the orbits of each planet over a span of time.
> 
> I believe I have all the pieces already. But how do I convert the 
> calculations into the functions a parametric object requires? For 
> example, what do I use for u and v?
> 
> Thanks.
> 
> 
> Mike


The latest version of the scene can now be downloaded from the Object 
Collection.

http://lib.povray.org/searchcollection/index2.php?objectName=SolarSystemOrrery&version=1.0&contributorTag=SharkD


Mike


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From: Mike Horvath
Subject: Re: Planetarium
Date: 15 Sep 2018 06:43:35
Message: <5b9ce257$1@news.povray.org>
I have textures, but do not know how to orient them with respect to the 
axial tilt, orbit and sun. Is anyone familiar with how to do this?


Mike


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From: Stephen
Subject: Re: Planetarium
Date: 15 Sep 2018 06:58:10
Message: <5b9ce5c2$1@news.povray.org>
On 15/09/2018 11:43, Mike Horvath wrote:
> I have textures, but do not know how to orient them with respect to the 
> axial tilt, orbit and sun. Is anyone familiar with how to do this?
> 
> 
> Mike

For Z up Left handed scenes.


texture {
   pigment {
     image_map{
       png "F:\Graphics\B3D Data\Maps\Planets\Earth\EarthMap2.png"
       interpolate 2
       map_type 1
     }
     rotate    <20.000,0.000,0.000>
   }

Then for orientation in an orbit. Rotate the sphere the planet texture 
will follow.

-- 

Regards
     Stephen


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From: Stephen
Subject: Re: Planetarium
Date: 15 Sep 2018 07:13:38
Message: <5b9ce962$1@news.povray.org>
On 15/09/2018 11:58, Stephen wrote:
>      rotate    <20.000,0.000,0.000>

That might be -19 to -21 not rotate 20*x

-- 

Regards
     Stephen


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From: Mike Horvath
Subject: Re: Planetarium
Date: 15 Sep 2018 08:11:44
Message: <5b9cf700$1@news.povray.org>
On 9/15/2018 6:58 AM, Stephen wrote:
> On 15/09/2018 11:43, Mike Horvath wrote:
>> I have textures, but do not know how to orient them with respect to 
>> the axial tilt, orbit and sun. Is anyone familiar with how to do this?
>>
>>
>> Mike
> 
> For Z up Left handed scenes.
> 
> 
> texture {
>    pigment {
>      image_map{
>        png "F:\Graphics\B3D Data\Maps\Planets\Earth\EarthMap2.png"
>        interpolate 2
>        map_type 1
>      }
>      rotate    <20.000,0.000,0.000>
>    }
> 
> Then for orientation in an orbit. Rotate the sphere the planet texture 
> will follow.
> 

Thanks. But which direction does the axis tilt with respect to the Sun 
on a given day?


Mike


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From: Stephen
Subject: Re: Planetarium
Date: 15 Sep 2018 09:01:34
Message: <5b9d02ae$1@news.povray.org>
On 15/09/2018 13:11, Mike Horvath wrote:
> On 9/15/2018 6:58 AM, Stephen wrote:
>> On 15/09/2018 11:43, Mike Horvath wrote:
>>> I have textures, but do not know how to orient them with respect to 
>>> the axial tilt, orbit and sun. Is anyone familiar with how to do this?
>>>
>>>
>>> Mike
>>
>> For Z up Left handed scenes.
>>
>>
>> texture {
>>    pigment {
>>      image_map{
>>        png "F:\Graphics\B3D Data\Maps\Planets\Earth\EarthMap2.png"
>>        interpolate 2
>>        map_type 1
>>      }
>>      rotate    <20.000,0.000,0.000>
>>    }
>>
>> Then for orientation in an orbit. Rotate the sphere the planet texture 
>> will follow.
>>
> 
> Thanks. But which direction does the axis tilt with respect to the Sun 
> on a given day?
> 
> 


Earth currently has an axial tilt of about 23.4° and the angle does not 
change. With respect to the Sun on a given day, it depends on there it 
is in its orbit.
https://en.wikipedia.org/wiki/Axial_tilt#Earth

So if you start your Planetarium at the summer or winter equinox. The 
mechanics will take care of themselves.
I think. :)



-- 

Regards
     Stephen


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From: Mike Horvath
Subject: Re: Planetarium
Date: 16 Sep 2018 14:31:41
Message: <5b9ea18d@news.povray.org>
Latest version is attached. It is *very* close, but the Earth is off by 
about one month's worth of travel.

Here is the document I am using as a guide:

https://ssd.jpl.nasa.gov/txt/aprx_pos_planets.pdf

And I am using this website to compare my render to:

https://in-the-sky.org/solarsystem.php

Set it to JD 2458376.5, which is equivalent to A.D. 2018 Sep 15.

I am not sure where my calculations have gone wrong.


Mike


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Attachments:
Download 'orrery_sphere_trail_new.pov.txt' (25 KB)

From: Mike Horvath
Subject: Re: Planetarium
Date: 16 Sep 2018 14:53:43
Message: <5b9ea6b7$1@news.povray.org>
On 9/16/2018 2:31 PM, Mike Horvath wrote:
> Latest version is attached. It is *very* close, but the Earth is off by 
> about one month's worth of travel.
> 
> Here is the document I am using as a guide:
> 
> https://ssd.jpl.nasa.gov/txt/aprx_pos_planets.pdf
> 
> And I am using this website to compare my render to:
> 
> https://in-the-sky.org/solarsystem.php
> 
> Set it to JD 2458376.5, which is equivalent to A.D. 2018 Sep 15.
> 
> I am not sure where my calculations have gone wrong.
> 
> 
> Mike


If you zoom out, Jupiter is also in the wrong place, so Maybe my results 
are *not* so close after all.


Mike


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From: Mike Horvath
Subject: Re: Planetarium
Date: 16 Sep 2018 22:49:40
Message: <5b9f1644$1@news.povray.org>
Updated the scene. It is working correctly now.

:)


Mike


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Attachments:
Download 'orrery_sphere_trail_b.pov.txt' (29 KB)

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