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I am building some physical models and animations that will travel in
and out of earth's atmosphere. I don't need photorealism, but I would
like something that looks better than what I have now:
http://www.launchloop.com/AtmosphereHack01
That is the result of 3 days of learning about POV-Ray, and a lot of
plagiarism of other designs (thanks, folks!). The page has a big (20MB)
SWF animation, and the .INI and .POV files that made it. The page is
a wiki, so you can add comments directly to the page (after registering).
Questions:
I am still looking for a good star model - like a map of the real
stars projected onto the sphere of the sky, not fake ones that dither
between animation frames.
I would also like to find a better black/blue/white horizon model than
the kludge I hacked up with media/emission .
Since I will be hanging a lot of detailed structure in the frame
(much of it off screen), rendering time will become an issue, and
making this draw faster would be nice.
I would like to be able to "force the seed" for random number
generation - any way to do that, besides hacking the POV-Ray code?
Any suggestions? BTW, I am a lousy programmer, and the code is
poorly commented, so if bad style is offensive, please do not read
it within an hour of eating :-)
Keith
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"Keith Lofstrom" <keithl AT kl dash ic dot com> wrote:
> I am building some physical models and animations that will travel in
> and out of earth's atmosphere. I don't need photorealism, but I would
> like something that looks better than what I have now:
>
> http://www.launchloop.com/AtmosphereHack01
>
> That is the result of 3 days of learning about POV-Ray, and a lot of
> plagiarism of other designs (thanks, folks!). The page has a big (20MB)
> SWF animation, and the .INI and .POV files that made it. The page is
> a wiki, so you can add comments directly to the page (after registering).
>
> Questions:
>
> I am still looking for a good star model - like a map of the real
> stars projected onto the sphere of the sky, not fake ones that dither
> between animation frames.
>
> I would also like to find a better black/blue/white horizon model than
> the kludge I hacked up with media/emission .
>
> Since I will be hanging a lot of detailed structure in the frame
> (much of it off screen), rendering time will become an issue, and
> making this draw faster would be nice.
>
> I would like to be able to "force the seed" for random number
> generation - any way to do that, besides hacking the POV-Ray code?
>
>
> Any suggestions? BTW, I am a lousy programmer, and the code is
> poorly commented, so if bad style is offensive, please do not read
> it within an hour of eating :-)
>
> Keith
Atmosphere and Media:
The first impression I had when looking over the code was that emission media is
the wring type for simulating the atmosphere - scattering is probably much
closer (and considerably slower). Emission, as the name implies, appears to be
lit when no light is on it. Scattering responds to light by scattering the
color supplied (i.e. reflecting some of it towards the camera, so it is lit
only where light shines on it, and absorbing that same color). Sometimes when
using scattering, you need a greater amount of control over the amount of light
absorbed. In cases like that, I use scattering with an extinction of 0, then
put in an absorption block.
Rendering speed:
In my experience with povray, very complex objects tend to be slow during
parsing (especially if there are a lot of macros or file operations), but not
that bad during tracing (except when the complex shape is used as a container
for a media object, has a lot of reflection/refraction, or is a photon target).
Random Numbers:
As for forcing the seed, I didn't see use of the rand() function in your code,
but you can set the seed for pseudo-random numbers by using the seed()
function:
// ----------- code:
#local MySeed = seed(7);
#local MyRand01 = rand(MySeed); // each call to rand will yield the
#local MyRand02 = rand(MySeed); // next number in the random stream
#local MyRand03 = rand(MySeed); // seeded by MySeed
// ----------- end code
If you are talking about the pseudo-random aspects of textures, the seed cannot
be directly controlled, but doing so is VERY rarely required, since the
textures can be thought of as functions in 3D space: If you don't see parts
you like, you can "translate in" another portion of the texture. Likewise, if
there is a portion of the texture you really like, you can apply the texture on
the object before transforming it:
// ----------- code:
sphere
{
<0,0,0>, 1
pigment{
bozo
color_map{
[ 0.00 color rgb <1,0,0> ]
[ 1.00 color rgb <0,0,1> ]
}
}
translate <-2,0,0>
}
sphere // looks the same, but different location
{
<0,0,0>, 1
pigment{
bozo
color_map{
[ 0.00 color rgb <1,0,0> ]
[ 1.00 color rgb <0,0,1> ]
}
}
translate <2,0,0>
}
sphere // looks different because it was tranformed before texturing
{
<0,0,0>, 1
translate <0,2,0>
pigment{
bozo
color_map{
[ 0.00 color rgb <1,0,0> ]
[ 1.00 color rgb <0,0,1> ]
}
}
translate <0,-2,0>
}
// ----------- end code
As for the star model, it seems to me that someone made an include a while back
- check the community section, I think there was a link in there.
-Reactor
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"Keith Lofstrom" <keithl AT kl dash ic dot com> wrote:
> I would like to be able to "force the seed" for random number
> generation - any way to do that, besides hacking the POV-Ray code?
What exactly do you mean?
SDL random number streams are always force-seeded from your scene code.
POV-Ray's internal RNGs are force-seeded, too, though the seeds are hard-coded
so you cannot directly tweak the value. But I wonder what the benefit of that
would be? After all, you cannot even control when numbers are pulled from the
streams, so what use would it be to control the start values?
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> I am building some physical models and animations that will travel in
> and out of earth's atmosphere. I don't need photorealism, but I would
> like something that looks better than what I have now:
>
> http://www.launchloop.com/AtmosphereHack01
>
> That is the result of 3 days of learning about POV-Ray, and a lot of
> plagiarism of other designs (thanks, folks!). The page has a big (20MB)
> SWF animation, and the .INI and .POV files that made it. The page is
> a wiki, so you can add comments directly to the page (after registering).
>
> Questions:
>
> I am still looking for a good star model - like a map of the real
> stars projected onto the sphere of the sky, not fake ones that dither
> between animation frames.
>
> I would also like to find a better black/blue/white horizon model than
> the kludge I hacked up with media/emission .
For a realistic athmosphere, you need scattering media. The drawback is
that it takes longer to render than emissive media.
>
> Since I will be hanging a lot of detailed structure in the frame
> (much of it off screen), rendering time will become an issue, and
> making this draw faster would be nice.
If most of your textures are mate and those off screen objects don't
cast shadows on the visible objects, they mostly don't affect the
rendering speed.
They will, owever, affect the parsing time.
If you use a macro frequently, like in a loop or nested loops, you
should place them in the file where they are used the most, or the main
POV file.
>
> I would like to be able to "force the seed" for random number
> generation - any way to do that, besides hacking the POV-Ray code?
The random number generator use a user provided seed and never change
from render to render. So, there is no choice BUT to force seed it.
The "random" patterns also don't change between renders, unless you
scale, rotate or translate them.
There are 2 "realy" random features:
crand and jitter.
crand is a finish element that should be avoided.
jitter is used in antialiasing and, optionaly, with area_light and media.
>
>
> Any suggestions? BTW, I am a lousy programmer, and the code is
> poorly commented, so if bad style is offensive, please do not read
> it within an hour of eating :-)
>
> Keith
>
>
>
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