POV-Ray : Newsgroups : povray.binaries.images : Shadow on Earth? Server Time
6 May 2024 18:05:33 EDT (-0400)
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From: omniverse
Subject: Re: Shadow on Earth?
Date: 20 Jul 2016 13:55:00
Message: <web.578fbab780911a1eb1933f770@news.povray.org>
Doctor John <j.g### [at] gmailcom> wrote:
> If you intend to use this as an animation, don't
> forget to rotate the clouds (possibly at a slightly different rate to
> the earth).

And spin Earth west to east, note the "-" for that: rotate -360*clock

Unless there's another reason to have the atmosphere not show below Earth's
surface you won't need to use CSG difference, a single sphere alone will be
okay.

I think the answers given already have helped solve the problem.
Texture finish was trouble, as said, and scaling can be done other ways. I would
have began with a sphere {0,1 and then scaled them after image map and media.
Just be aware that media scaled after applied can change the affect,
historically anyway:

sphere {0,1 ... media { ... scale 0.5} scale 10}

Unfortunately I haven't kept up with that subject, I have not done much in
recent years, so please excuse me if media now retains original qualities when
scaling it's containing objects. Maybe it still scales (thickness or thinness).


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From: Stephen
Subject: Re: Shadow on Earth?
Date: 20 Jul 2016 15:41:44
Message: <578fd3f8$1@news.povray.org>
On 7/20/2016 6:18 PM, clipka wrote:
> Am 20.07.2016 um 19:06 schrieb Stephen:

>
> OOoooh -- careful! This Code Monkey could accidently type a few lines of
> code that make POV-Ray crash specifically on /your/ computer. So stop
> talking, human, and hand over the bananas! ;)
>

Interesting that you say that.
When I was working at Taronga Zoo, in Sydney. The keepers in the Monkey 
house used bananas as part of their alarm system. Every night they put a 
banana beside a window. If in the morning the banana was gone. Then the 
monkeys had gotten off of the inner enclosure.


>>
>> Clouds are problematic especially in an animation. The simplest way
>> would be to use an image map.
>
> Tried that, and found it looking unconvincing. The best thing I've
> managed to come up with so far was a combination of an image map and a
> spherical function to create media with a cloud-ish density distribution.
>
> It would be cool if we had a set of cloud image maps epresenting cloud
> densities at different altitudes, but I guess such a thing doesn't exist
> (yet).
>

The big problem that I come up against is that All of these types of 
animations are cyclic and our weather system does show the same behaviour.

-- 

Regards
     Stephen


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From: Alain
Subject: Re: Shadow on Earth?
Date: 21 Jul 2016 16:10:06
Message: <57912c1e@news.povray.org>

> I'm now working hard on my assignment for my CG class at college, in which I'm
> trying to make a realistic earth animation.
> I used "difference" to create something like atmosphere right outside earth, and
> in which I also used emission for making the atmosphere glow. And this is where
> I'm facing a problem.
>
> When I set a light_source from a distance, there is no shadow cast on earth.
> Here I paste the source code:
>
> light_source {
>  <100, 0, 50>
>  color White
>  spotlight
>  fade_distance 100
>  fade_power 10
>  point_at <0, 0, 0>
> }

Why use a spotlight?
Why use fading?

Given the distance from the Sun to the Earth, you are better using a 
parallel light without any fading. Think about it, the Sun-Earth 
distance is over 10000000 times the Earth's radius.
The difference in the illumination over the moon's orbit 's diameter is 
effectively negligible.

fade_power ONLY realistic value is 2.
fade_sidtance should be about the appearent diameter of a light's diameter.
If the light becomes to dark, you can increase it's intensity 
arbitrarily by as much as you need.

Try this one:
light_source{<100, 0, 50>*10 rgb 2 parallel}

>
> // earth
> sphere {
>     <0, 0, 0>, 3.5
>     texture {
>         pigment {
>       image_map {
>                 jpeg "textures/earth.jpg"
>                 map_type 1
>             }
>             scale 3.5

This scalling is useless.

>         }
>
>         finish {
>             ambient 1
>             diffuse 3

Beter use ambient 0, diffuse 0.6 here.
ambient 1 mean that your earth is actualy glowing.
diffuse 3 mean that it give off 3 times as much light as it receive from 
the Sun.

>         }
>
>         rotate y*-135
>         rotate x*35
>     }
>     // rotation
>     rotate <0, 360*clock, 0>
> }
>
> // atmosphere emission
> difference {
>   sphere { <0, 0, 0>, 3.54 }
>   sphere { <0, 0, 0>, 3.0 }
>
>   material {
>    texture{
>    pigment { rgbt 1 }
>    }
>
>    interior {
>      media {
>        emission 0.5

A GLOWING atmosphere? Last time I checked, Earth's atmosphere scatters 
the light and don't emit any.

>        //scattering { 5 color rgb 0.01 eccentricity 0.56 }

The proper model is scattering{4 rgb 0.01}

>        density {
>          spherical density_map {
>        [ 0.0  rgb 0.0 ]
>           [ 0.5294*0.25e-6  rgb <0.02, 0.05, 0.2>*0.07 ]
>           [ 0.5294*0.4e-6   rgb <0.02, 0.07, 0.3>*0.32 ]
>           [ 0.5294*0.5e-6   rgb <0.08, 0.18, 0.4>*0.5 ]
>           [ 0.5412*0.6e-6   rgb <0.08, 0.18, 0.4>*0.9 ]
>           [ 0.5471*0.65e-6  rgb <0.08, 0.18, 0.4>*1.5 ]
>           [ 0.5471*0.675e-6 rgb <0.08, 0.18, 0.4>*4.5 ]
>           [ 0.5471*0.71e-6  rgb <0.08, 0.18, 0.4>*12 ]
>          }
>      scale 100
>        }
>      }
>    }
>   }
>
>   hollow on
> }
>
> And below I attach the rendered result for now.
>
> How can I solve this problem? I'd appreciate it if someone could help.
> I'm not a native English speaker, so I'm very sorry for my poor English... I
> really wish I didn't use impolite expressions!
>
> Thanks.
>

Alain


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From: Cousin Ricky
Subject: Re: Shadow on Earth?
Date: 23 Jul 2016 01:00:01
Message: <web.5792f99980911a1eb484452a0@news.povray.org>
Alain <kua### [at] videotronca> wrote:
>  Think about it, the Sun-Earth
> distance is over 10000000 times the Earth's radius.

I get 23481 times, a far cry from 10 million.


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