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I was wondering if anyone could direct me toward a scene with a
realistic daytime sky, clouds, haze and sun that I could reuse in my own
scene (I have already determined units of measurement for my scene).
Thanks!
-Mike
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SharkD wrote:
> I was wondering if anyone could direct me toward a scene with a
> realistic daytime sky, clouds, haze and sun that I could reuse in my own
> scene (I have already determined units of measurement for my scene).
>
> Thanks!
>
> -Mike
Such things are very hard to port between scenes due to scale. At
least, assuming you're using media for the abovementioned effects.
...Chambers
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SharkD a écrit :
> I was wondering if anyone could direct me toward a scene with a
> realistic daytime sky, clouds, haze and sun that I could reuse in my own
> scene (I have already determined units of measurement for my scene).
>
> Thanks!
>
> -Mike
Most of those are hard to port, especialy if the scale of the scenes
differs.
The daytime sky can be done with a sky_sphere to provide the backdrop
for the other elements. Usualy, all you need is a nice gradient.
The haze and clouds are harder to port, and, in some case, it's not
possible.
Realistic clouds often require the use of media. Same for the haze.
If you change the scale, you need to change the density, and possibly
the pattern(s) used.
If your POV units represent a smaller unit (feet to meter for example)
that the original, the media will get to thick.
The easiest part, is the Sun. Look at the lightsys and sunpos.
Alain
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With a bit of tooling around I managed to make it work. I created a
panorama using it that you can find here:
http://isometricland.com/gearhead/ghpanotour.htm
-Mike
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I'm trying to scale the volumetric clouds (in particular the flat "cloud
bank") found on this page:
http://www.geocities.com/evilsnack/tut01.htm
The Povray docs only briefly mention what you need to do in order to
scale interior media. The example in the docs is for an emission media
with no explicitly defined density map. The clouds script however is a
scattering media with a density map (see below). Have I done things
correctly?
#local Inc_Scale_Amount = Width;
#local Dec_Scale_Amount = sqrt(3) / vlength(Inc_Scale_Amount);
#local pigCloudBank = pigment
{
average
pigment_map {[1 planar][1 granite scale 50]}
}
box
{
<-200,-2,-200>,<200,2,200>
hollow
texture {pigment {rgbt 1}}
interior
{
media
{
scattering {1, 0.5 * Dec_Scale_Amount}
method 3
// samples 30, 100
intervals 1
density
{
pigment_pattern {pigCloudBank}
density_map {[.6 rgb 0][.61 rgb 1]}
}
}
}
scale Inc_Scale_Amount
translate y * Width * 8
}
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SharkD schrieb:
> #local Inc_Scale_Amount = Width;
> #local Dec_Scale_Amount = sqrt(3) / vlength(Inc_Scale_Amount);
What is "Width"?
It should be a scalar, otherwise you'll be running into trouble, as
you'd need an anisotropic media density (i.e. different density
depending on the orientation of the traversing ray) for a proper job.
Then if it is a scalar, the above values should actually be:
#local Inc_Scale_Amount = Width;
#local Dec_Scale_Amount = 1 / Width;
If you absolutely need it to be a vector, you'll probably want the
"thickness" to remain the same, i.e. retain the effective absorption in
Y direction; you'd achieve this by defining the values as:
#local Inc_Scale_Amount = Width;
#local Dec_Scale_Amount = 1 / Width.y;
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clipka wrote:
> SharkD schrieb:
>> #local Inc_Scale_Amount = Width;
>> #local Dec_Scale_Amount = sqrt(3) / vlength(Inc_Scale_Amount);
>
> What is "Width"?
>
> It should be a scalar, otherwise you'll be running into trouble, as
> you'd need an anisotropic media density (i.e. different density
> depending on the orientation of the traversing ray) for a proper job.
Good catch! Yes, "Width" is a scalar. However, even after fixing this
the clouds don't look quite like the image on the website I linked to.
The clouds are supposed to be dark underneath, but aren't when I render
the scene.
light_source
{
<+3000, +6000, -7000,> * Width
rgb 2.0
parallel
}
The location of the light source is well above the clouds. But, the
light source is twice as bright. How might I modify the media to
compensate? I suppose I could contain the clouds in a light group with a
dimmer light source, but I'd rather avoid this since it affects things
like shadows.
-Mike
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SharkD wrote:
> Good catch! Yes, "Width" is a scalar. However, even after fixing this
> the clouds don't look quite like the image on the website I linked to.
> The clouds are supposed to be dark underneath, but aren't when I render
> the scene.
Also, when I do diminish the light source, the clouds still become less
"dark" the farther away they are in the scene. I might expect this from
a point light source due to the angle of the light, but my light source
is parallel so it should be immune.
-Mike
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SharkD <mik### [at] gmail com> wrote:
The clouds are supposed to be dark underneath, but aren't when I render
> the scene.
> The location of the light source is well above the clouds. But, the
> light source is twice as bright. How might I modify the media to
> compensate? I suppose I could contain the clouds in a light group with a
> dimmer light source, but I'd rather avoid this since it affects things
> like shadows.
>
> -Mike
You can try increasing the extinction value in the scattering block. By
default, extinction is 1.0, but you can increase it to something higher to
increase the amount of light absorbed by the media without actually thickening
the media. By doing this, though, your clouds may have a very strong color
contrast with white at the tops and a very dark bottom. You can control the
contrast of the clouds by balancing the scattering media with absorption and
emission medias.
-Reactor
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Reactor wrote:
> You can try increasing the extinction value in the scattering block. By
> default, extinction is 1.0, but you can increase it to something higher to
> increase the amount of light absorbed by the media without actually thickening
> the media. By doing this, though, your clouds may have a very strong color
> contrast with white at the tops and a very dark bottom. You can control the
> contrast of the clouds by balancing the scattering media with absorption and
> emission medias.
>
>
> -Reactor
Thanks! Any tips on the increasing brightness problem I described in my
other post?
-Mike
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SharkD <mik### [at] gmailcom> wrote:
> Reactor wrote:
> > You can try increasing the extinction value in the scattering block. By
> > default, extinction is 1.0, but you can increase it to something higher to
> > increase the amount of light absorbed by the media without actually thickening
> > the media. By doing this, though, your clouds may have a very strong color
> > contrast with white at the tops and a very dark bottom. You can control the
> > contrast of the clouds by balancing the scattering media with absorption and
> > emission medias.
> >
> >
> > -Reactor
>
> Thanks! Any tips on the increasing brightness problem I described in my
> other post?
>
> -Mike
I'd have to see an example, but what you've described sounds kind of like
sampling artifacts Is the second sampling parameter still used with method 3?
try boosting the min samples to 50 and rendering only that small part of the
scene. If it is closer to what you expected, then it was caused by sampling
errors.
-Reactor
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Reactor wrote:
> I'd have to see an example, but what you've described sounds kind of like
> sampling artifacts Is the second sampling parameter still used with method 3?
> try boosting the min samples to 50 and rendering only that small part of the
> scene. If it is closer to what you expected, then it was caused by sampling
> errors.
>
> -Reactor
That helps, but it causes the scene to take a real long time to render.
Would splitting into multiple objects help?
-Mike
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Reactor a écrit :
> SharkD <mik### [at] gmailcom> wrote:
>> Reactor wrote:
>>> You can try increasing the extinction value in the scattering block. By
>>> default, extinction is 1.0, but you can increase it to something higher to
>>> increase the amount of light absorbed by the media without actually thickening
>>> the media. By doing this, though, your clouds may have a very strong color
>>> contrast with white at the tops and a very dark bottom. You can control the
>>> contrast of the clouds by balancing the scattering media with absorption and
>>> emission medias.
>>>
>>>
>>> -Reactor
>> Thanks! Any tips on the increasing brightness problem I described in my
>> other post?
>>
>> -Mike
>
> I'd have to see an example, but what you've described sounds kind of like
> sampling artifacts Is the second sampling parameter still used with method 3?
> try boosting the min samples to 50 and rendering only that small part of the
> scene. If it is closer to what you expected, then it was caused by sampling
> errors.
>
> -Reactor
>
>
Is the second sampling parameter still used with method 3?
No!
There is no longer a concept of min and max samples. Only samples.
Do I need to change the number of intervals?
NO! Leave it at 1. Otherwise, it's slow like thick molace in winter. It
can also cause artefacts. Increase the number of samples.
Alain
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SharkD <mik### [at] gmailcom> wrote:
> Reactor wrote:
> > I'd have to see an example, but what you've described sounds kind of like
> > sampling artifacts Is the second sampling parameter still used with method 3?
> > try boosting the min samples to 50 and rendering only that small part of the
> > scene. If it is closer to what you expected, then it was caused by sampling
> > errors.
> >
> > -Reactor
>
>
> That helps, but it causes the scene to take a real long time to render.
Yeah, scattering media does that.
> Would splitting into multiple objects help?
Probably not, unless you fit the media more tightly to the container shapes.
However, you could split it into multiple container shapes and use different
settings for those (if you wanted to).
-Reactor
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Alain <aze### [at] qwertyorg> wrote:
> Reactor a écrit :
> Is the second sampling parameter still used with method 3?
> No!
> There is no longer a concept of min and max samples. Only samples.
>
> Do I need to change the number of intervals?
> NO! Leave it at 1. Otherwise, it's slow like thick molace in winter. It
> can also cause artefacts. Increase the number of samples.
>
>
> Alain
Ah, thanks. I knew that about the intervals, but I wasn't sure about the
samples second parameter being ignored. On a somewhat related note, I am
becoming increasingly curious as to how his image will look.
-Reactor
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Reactor wrote:
> SharkD <mik### [at] gmailcom> wrote:
>> Reactor wrote:
>>> You can try increasing the extinction value in the scattering block. By
>>> default, extinction is 1.0, but you can increase it to something higher to
>>> increase the amount of light absorbed by the media without actually thickening
>>> the media. By doing this, though, your clouds may have a very strong color
>>> contrast with white at the tops and a very dark bottom. You can control the
>>> contrast of the clouds by balancing the scattering media with absorption and
>>> emission medias.
>>>
>>>
>>> -Reactor
>> Thanks! Any tips on the increasing brightness problem I described in my
>> other post?
>>
>> -Mike
>
> I'd have to see an example, but what you've described sounds kind of like
> sampling artifacts Is the second sampling parameter still used with method 3?
> try boosting the min samples to 50 and rendering only that small part of the
> scene. If it is closer to what you expected, then it was caused by sampling
> errors.
>
> -Reactor
>
>
Here's an example:
http://i421.photobucket.com/albums/pp292/SharkD2161/Support/gh_scene_outdoors_cubemap.png
Notice how the clouds are darker near the camera (at the top of the
image) and get lighter the farther away they are (toward the middle of
the image). The samples are already set pretty high:
samples 30, 100
-Mike
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SharkD schrieb:
> Notice how the clouds are darker near the camera (at the top of the
> image) and get lighter the farther away they are (toward the middle of
> the image). The samples are already set pretty high:
It appears to me they're much too thinned-out. So you get that bright
white far off where the ray hits shallow enough to traverse a
considerable distance in the clouds, but almost plain blue sky right above.
Also note that in reality, the far-off clouds would be hit at a less
shallow angle due to earth's curvature; maybe you can achieve a similar
effect by very slightly tilting the sky. Alternatively, you could use a
shell made out of actual gigantic spheres as your media container (you
may need to adjust your density pattern in that case though).
Another thing that looks weird is the apparent "stacking" - hard to tell
where that comes from. Maybe the geometry is way different from what I
think it is.
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Thanks for taking a look!
clipka wrote:
> It appears to me they're much too thinned-out. So you get that bright
> white far off where the ray hits shallow enough to traverse a
> considerable distance in the clouds, but almost plain blue sky right above.
I'll try fattening the layer up a little.
> Also note that in reality, the far-off clouds would be hit at a less
> shallow angle due to earth's curvature; maybe you can achieve a similar
> effect by very slightly tilting the sky. Alternatively, you could use a
> shell made out of actual gigantic spheres as your media container (you
> may need to adjust your density pattern in that case though).
Yes, but precision errors occur if I make the spheres *too* big. How big
would be big enough? In my scene 1 unit = 1 meter.
> Another thing that looks weird is the apparent "stacking" - hard to tell
> where that comes from. Maybe the geometry is way different from what I
> think it is.
Not sure what you mean by "stacking".
Thanks again!
-Mike
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SharkD schrieb:
> Yes, but precision errors occur if I make the spheres *too* big. How big
> would be big enough? In my scene 1 unit = 1 meter.
Don't worry about precision issues.
For exact scale, the atmosphere should have a radius of some 6e+6 units,
which is indeed comparatively close to the distance limit at which
objects disappear; still, it's within that limit. Also note that this
distance cut-off is /relative/ to a ray's origin (e.g. the camera), and
with an atmosphere thickness of just a few 1000 units and the camera
just a few units away from the ground, you'll only be able to see a
small section of the atmosphere anyway. Somewhere between 1e+5 and 1e+6
units I'd guesstimate - dunno.
Bounding is no issue either: You'd be inside the sphere anyway, so the
bounding box will be intersected anyway, so even if it is of low
precision or turned off entirely, that doesn't make a difference.
And don't worry either about possible loss of details due to the center
of the atmosphere being quite far away from your details: As POV-Ray
uses double-precision math, a scene encompassing the whole earth would
still allow headroom for details as small as a nanometer(!), so there
should be enough headroom.
Make sure though to center your area of interest at <0,0,0>, so don't
make that the center of your atmosphere.
>> Another thing that looks weird is the apparent "stacking" - hard to
>> tell where that comes from. Maybe the geometry is way different from
>> what I think it is.
>
> Not sure what you mean by "stacking".
Well, the clouds look somewhat like the closer(?) ones are thinned-out
copies of the further-off(?) ones. Or as if they were actually as far
off as what they appear to be copying, just higher.
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clipka wrote:
> SharkD schrieb:
>> Yes, but precision errors occur if I make the spheres *too* big. How
>> big would be big enough? In my scene 1 unit = 1 meter.
>
> Don't worry about precision issues.
>
> For exact scale, the atmosphere should have a radius of some 6e+6 units,
> which is indeed comparatively close to the distance limit at which
> objects disappear; still, it's within that limit. Also note that this
> distance cut-off is /relative/ to a ray's origin (e.g. the camera), and
> with an atmosphere thickness of just a few 1000 units and the camera
> just a few units away from the ground, you'll only be able to see a
> small section of the atmosphere anyway. Somewhere between 1e+5 and 1e+6
> units I'd guesstimate - dunno.
Correction, I just double-checked and 4 units = 1 meter. I hope that
doesn't affect anything.
-Mike
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