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Hi,
I admit, I never worked with fog or media before, and thus I don't
really even know, what exactly to look for in the help file. When
looking up there for FOG, I did not see what I need.
Thus I am asking here for some starting advise.
My intention is, to create a spherical object that appears like a
blurred fog, wish shades of glowing orange inside. There is no shark
outside edge. Just imagine a glowing, but relatively dim sun. I wonder,
if FOG or MEDIA can do the trick, but need here some advises what
exactly to look for inside the Help file. Thanks.
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Le 15-12-17 17:23, Sven Littkowski a écrit :
> Hi,
>
> I admit, I never worked with fog or media before, and thus I don't
> really even know, what exactly to look for in the help file. When
> looking up there for FOG, I did not see what I need.
>
> Thus I am asking here for some starting advise.
>
> My intention is, to create a spherical object that appears like a
> blurred fog, wish shades of glowing orange inside. There is no shark
> outside edge. Just imagine a glowing, but relatively dim sun. I wonder,
> if FOG or MEDIA can do the trick, but need here some advises what
> exactly to look for inside the Help file. Thanks.
>
fog is not what you need. It can't be shaped in any way.
What you need is media.
As you want a glowing thing, emissive media seems to impose itself.
You probably don't want your glowing media to fill the whole scene, so,
you need to contain it in something. A good shape, in your case, is the
sphere.
Here's a minimal example:
sphere{
0, 1
pigment{rgbt 1} //make it totaly invisible
hollow // enable it to contain your media
// the "magic" start here
interior{
media{ emission 1 // adjust as needed
density{ spherical }
// start at 1 at <0,0,0> and drop to zero at radius 1
}
scale Dimention
translate Location
}
This will give you a spherical shaped area of luminous gray to white
media at the origin that you can scale as wanted, then, translate/move
to the desired location.
If you create the sphere elsewhere, the media pattern will NOT be placed
adequately.
If you scale, the media effect will change proportionately.
The value for emission can be a colour and it's value is not limited to
the 0..1 range.
emission<10, 100, 1000> is legal as is emission<-1, 1, 1>
The pattern used can have a color_map that can change the effective colour.
If you add some turbulence to the pattern, you need to make the
containing sphere larger: turbulence 0.5 need a sphere's radius of about
1.5, otherwise, part of it will be clipped.
If you use radiosity, adding "media on" in the radiosity block will
allow that media to illuminate it's surrounding. In a normal scene, you
need to add an actual light_source to have it shed any light around.
Beter to use an area_light in this case.
Alain
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Alan, this is a great start-up help you have given, my appreciation! I
started already to make experiments with it.
Still, there is something I need to know:
I want that the media covers up a sphere, let's say, of a radius of 1
unit. Just outside that 1-unit-radius sphere, the density should fade
down to 0.0 at a distance of 0.3 units to the outside of that sphere.
That means, the density does not decrease constantly from center to 1.3
units away. How can I implement it this way?
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Besides this all, it seems, when trying to look up MEDIA and DENSITY
inside the help file, they were forgotten to be cross-linked to. I also
tried successly to click these keywords inside the scene source code and
then pressing "F1" - this just opens up the Help File's start page. Can
that be? Do you all have the same experience? Please test.
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Alan, I experimented a little bit. At the moment, using your code and
also (now that I know what to look for) POV-Ray's example files, I am
ending up with this:
sphere
{
< 0.0, 0.0, 0.0 > 10.0
pigment { rgbt 1.0 } //makes it invisible
hollow // enable it to contain your media
interior // the "magic" starts here
{
media
{
emission 0.5
intervals 1
samples 5
method 3
density
{
spherical
color_map
{
[ 0.0 color rgb < 0.0, 0.0, 0.0 > ]
[ 0.1 color rgb < 0.74902, 0.34118, 0.22353 > /4 ]
[ 1.0 color rgb < 0.74902, 0.34118, 0.22353 > ]
}
} // starts at 1 at <0,0,0> and drops to zero at radius 1
}
}
scale 10.0
translate < 0.0, 0.0, 0.0 >
}
cylinder
{
< 0.0, 0.0, -50.0 > < 0.0, 0.0, 50.0 > 2.50
pigment { rgb < 1.0, 0.5, 0.0 > }
}
The media sphere, and for test purposes a cylinder.
I am quite happy, but would like still to have the same high density
within 1.0 units from the center, and then a fading out from 1.0 to 1.3.
The fading out I achieve, is not regular enough - it seems to end quite
fast.
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Le 15-12-17 21:09, Sven Littkowski a écrit :
> Alan, this is a great start-up help you have given, my appreciation! I
> started already to make experiments with it.
>
> Still, there is something I need to know:
> I want that the media covers up a sphere, let's say, of a radius of 1
> unit. Just outside that 1-unit-radius sphere, the density should fade
> down to 0.0 at a distance of 0.3 units to the outside of that sphere.
>
> That means, the density does not decrease constantly from center to 1.3
> units away. How can I implement it this way?
>
By judiciously using a color_map as follow:
sphere{
0, 1
pigment{rgbt 1} //make it totaly invisible
hollow // enable it to contain your media
// the "magic" start here
interior{
media{ emission 1 // adjust as needed
density{ spherical color_map{[0 rgb 0][1-(1/1.3) rgb 1 ]}}
}
scale 1.3
// scale the sphere and the media as a single unit
translate Location
}
This way, for all values of the pattern that are larger than about 0.23
will have the maximum density. For those smaller, the density will
decrease much faster doen to zero.
If you need to increase the quality of the media in case of missing
details or banding, you increase the samples count. NEVER increase
intervals to any value larger than 1.
The defaults are:
method 3
samples 10
intervals 1
In my tests, I found that "samples 100 intervals 1" is much faster than
"samples 1, 5 intervals 5" and give a beter result.
Emissive media is the fastest to render, followed by absorbing and
scattering is the slowest.
Alain
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Le 15-12-17 21:11, Sven Littkowski a écrit :
> Besides this all, it seems, when trying to look up MEDIA and DENSITY
> inside the help file, they were forgotten to be cross-linked to. I also
> tried successly to click these keywords inside the scene source code and
> then pressing "F1" - this just opens up the Help File's start page. Can
> that be? Do you all have the same experience? Please test.
>
The help page you get is absolutely huge!
It contains material for ALL aspects of the scene.
The part about media is about 85% down, before the lengthy description
of the standard include files.
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This is strange - my Help File lacks functionality, it seems. Will check
out that problem later. The media works now the way I want it, and I am
very happy. Thanks a lot!
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On 18-12-2015 4:30, Sven Littkowski wrote:
> This is strange - my Help File lacks functionality, it seems. Will check
> out that problem later. The media works now the way I want it, and I am
> very happy. Thanks a lot!
>
The help file (F1) resident in POV-Ray has not been too good for some
time now nor is it entirely up-to-date. Many links are broken, some do
not exist. It would need a serious overhaul. However, The wiki page is
entirely up-to-date and of easy access:
http://wiki.povray.org/content/Documentation:Contents
--
Thomas
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Alan, for you I have attached a first rendering of my spaceship, using
the media as you told me. I still have to make some adjustments, but it
looks really neat on my little ship.
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Attachments:
Download 'sl - seneca ii - close view 1 km - wormhole generator - 002.jpg' (543 KB)
Preview of image 'sl - seneca ii - close view 1 km - wormhole generator - 002.jpg'
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