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I'm trying an outside scene on a cloudy day... it's the grass scene I have
been posting.
But the sky_sphere is always beautifully lit, while the rest of the scene is
essentially black.
Here are my settings, what's wrong?
global_settings {
assumed_gamma .8
ambient_light rgb .3
radiosity {
pretrace_start 0.08
pretrace_end 0.01
count 500
nearest_count 10
error_bound 0.02
recursion_limit 1
low_error_factor 0.2
gray_threshold 0.0
minimum_reuse 0.015
brightness 1
adc_bailout 0.01/2
}
Post a reply to this message
Attachments:
Download 'bad_rad.jpg' (5 KB)
Preview of image 'bad_rad.jpg'
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Bryan Valencia wrote:
> I'm trying an outside scene on a cloudy day... it's the grass scene I have
> been posting.
>
> But the sky_sphere is always beautifully lit, while the rest of the scene is
> essentially black.
>
> Here are my settings, what's wrong?
[snip...]
At least the recursion limit should be over 1 - use the default 3 for
starters and increase if needed. It determines basically how many times
the diffusing light can be reflected to lit other parts in scene. The
bigger the number, more accurate the result and slower the rendering. I
also suggest you start with the default values and specify/change only
those necessary. Now you change all the values and understand none of
them :)
Also, the ambient light level should be 0 for starters in radiosity
scenes. I suggest you set the default ambient light to 0 using:
#default{finish{ambient 0}}
You can do this also with "ambient_light rgb 0" in global settings. This
prevents objects from "glowing". If you need an object emitting light
you can specify ambient light individually when needed.
First learn to use count, brightness and error_bound. Test how they
affect your scene. Then experiment with the other options - one at a time.
And read the appropriate section in the docs.
Severi S.
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I'm sure the gurus can give you a better explanation but I will try
based on my experience. More importantly then radiosity settings is the
light source that you are using. If you are going pure radiosity for an
outdoors scene you will probably want to invest in an HDRI map and use
ML-POV. If you use a regular sky_sphere you are going to get a very
constant, dull illlumination of the scene. Of course this is basically the
illumination that you get on a cloudy day, but your image is still going to
render washed out. If the scene is to dark, try multiplying the colors in
the sky_sphere. Having the camera point at the sky_sphere will cause the
colors to clip out of range (the sky will look white), but often you need
much brighter values to properly illuminate the scene.
If you haven't done so already (its hard to judge from the resolution of
that image) add a point light to your scene. Pure radiosity is realistic
and artistic, but a dim, well place point light can bring out the shadows
and shades. Radiosity and light sources go good together when the scene is
setup properly. For example you could use an HDRI map of the sky and place
a point light lined up with the sun where the sun would be.
As far as your settings are concerned, a few adjustments could be made.
Contrary to what Severi said in his reply, I have found that anything more
then a recursion setting of 3 for a rad scene is overkill. Unless you have
an interior scene with alot of nooks, crannies, and diffuse lighting, you
probably won't need anything higher then a recursion level of 2. Your
setting of 1 is probably fine for now, especially if you use a point light.
Not only does raising this number kill your render time but it also washes
out the image. The extra light bouncing around will dull your shading,
however, you can counter this by raising the assumed_gama.
Your error_bound is way too low. If your illumination is pretty broad
or you are using point lights you could probably get away with an
error_bound of 1.0. I typically don't lower that value further then 0.5
because, not only does the render time go up, but the artifacts are
impossible to get rid of.
Like Severi said, that ambient light should be 0. Unless the object is
a light source, it should not have a ambient light or else its going to
interfere the natural illumination of the scene. You can try raising the
brightness in the rad settings if the scene is too dim. Hope this helps
some.
Skip
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Severi Salminen wrote:
> You can do this also with "ambient_light rgb 0" in global settings. This
> prevents objects from "glowing". If you need an object emitting light
> you can specify ambient light individually when needed.
It looks that if I put "ambient_light rgb 0" in the global settings,
then set ambient to some high number in an individual finish, I don't
get the "glow" effect if I'm using radiosity. It looks like to get a
"lightbulb" doing radiosity, I have to edit all the textures I'm using
to add "ambient 0" to the texture, then leave global ambience at a
postitive number, and set "ambient 3" on the lightbulb itself?
Just trying to figure this one out... :-) Clues appriciated.
--
Darren New, San Diego CA USA (PST)
I am in geosynchronous orbit, supported by
a quantum photon exchange drive....
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I usually set ambient_light to rgb 1 and then go through and make sure that
all objects in the scene that I do not specifically wanted to emit light are
set to ambient 0. For things like the sky, I ramp up the ambient value as
high as the scene will permit (for example, 1.5 or 2). Yes, the sky or
whatever looks overexposed, but it would also probably look like that in a
photo.
At least this is my theory.
Aaron
"Bryan Valencia" <bry### [at] 209software com> wrote in message
news:406b003f@news.povray.org...
> I'm trying an outside scene on a cloudy day... it's the grass scene I have
> been posting.
>
> But the sky_sphere is always beautifully lit, while the rest of the scene
is
> essentially black.
>
> Here are my settings, what's wrong?
> global_settings {
> assumed_gamma .8
> ambient_light rgb .3
>
> radiosity {
> pretrace_start 0.08
> pretrace_end 0.01
> count 500
>
> nearest_count 10
> error_bound 0.02
> recursion_limit 1
>
> low_error_factor 0.2
> gray_threshold 0.0
> minimum_reuse 0.015
> brightness 1
>
> adc_bailout 0.01/2
> }
>
>
>
>
Post a reply to this message
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Bryan Valencia wrote:
> I'm trying an outside scene on a cloudy day... it's the grass scene I have
> been posting.
>
> But the sky_sphere is always beautifully lit, while the rest of the scene is
> essentially black.
>
> Here are my settings, what's wrong?
> global_settings {
> assumed_gamma .8
> ambient_light rgb .3
>
> radiosity {
> pretrace_start 0.08
> pretrace_end 0.01
> count 500
>
> nearest_count 10
> error_bound 0.02
> recursion_limit 1
>
> low_error_factor 0.2
> gray_threshold 0.0
> minimum_reuse 0.015
> brightness 1
>
> adc_bailout 0.01/2
> }
I'm going to go ahead and partly disagree with everyone here... ;D
First, the ambient_light global setting doesn't set a default ambient
finish (that's what #default is for); it sets an ambient multiplier. So
if you're using ambient finishes ANYWHERE in your scene, they will be
multiplied by .3. If this is affecting your sky_sphere, that would be
the cause of your problem.
Second, your count is way too high for an outdoor scene with a large
open sky; you're wasting a lot of cycles on quality that you probably
can't see. Try using 100 or less (30 would be plenty for test renders)
and don't increase it unless artifacting is a problem with the settings
you're using for the final render.
Likewise, your error_bound is way too low for most outdoor scenes;
pretty much anything below .3 or so is only useful if you want really
detailed radiosity shadows. Try a setting of .5 or so.
Your low_error_factor can probably be set to 1, especially if you decide
to use a smaller error_bound. (Go look it up.)
Some people on these groups will recommend a ridiculously high
recursion_limit. Don't listen to them, they're fools. Most outdoor
scenes with wide open skies can get by with a recursion_limit of 1;
indoor scenes will usually be fine with a recursion_limit of 2. The
difference between 2 and 3 in most scenes is nearly invisible, and
higher settings are useless for anything except *very* indirect
lighting.. and even then, you'd probably want 16-bit output and
post-processing to make any use of the data.
-Xplo
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Darren New wrote:
>
> It looks that if I put "ambient_light rgb 0" in the global settings,
> then set ambient to some high number in an individual finish, I don't
> get the "glow" effect if I'm using radiosity. It looks like to get a
> "lightbulb" doing radiosity, I have to edit all the textures I'm using
> to add "ambient 0" to the texture, then leave global ambience at a
> postitive number, and set "ambient 3" on the lightbulb itself?
>
> Just trying to figure this one out... :-) Clues appriciated.
If you use "ambient_light rgb 0" in the global settings, it will have
the effect of multiplying all your ambient finishes by 0. Feeling clued yet?
-Xplo
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The other thing I do is always use the settings in rad_def.inc.
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Xplo Eristotle wrote:
> If you use "ambient_light rgb 0" in the global settings, it will have
> the effect of multiplying all your ambient finishes by 0. Feeling clued
> yet?
Right. I saw that in the docs. So I can't do that to (say) switch from
normal lighting to radiosity, because all my lightbulbs disappear.
Instead, I apparently have to edit every texture used to remove any
ambient from them individually? OK, that's what I thought. I thought
maybe there was something I could put in a texture perhaps that would
say "Make this look ambient even tho ambient_light=0". A kind of
absolute ambient value or some such.
--
Darren New, San Diego CA USA (PST)
I am in geosynchronous orbit, supported by
a quantum photon exchange drive....
Post a reply to this message
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First of all, thanks for all the replies, there's more material here than in
the help. I know - I really did look. In fact, if you'll all turn to
section 4.1.3 of the help and scroll to the bottom, you'll see these exact
radiosity settings.
If you look at my last grass_test image - I used a far away point light and
didn't like the effect. It seemed "sunny" on the objects, on a cloudy day.
That's why I even tried rad lighting.
question: will lowering count make the lighting down between the grass and
the Earth funky?
Also, I have added a radiosity "light" inside the spaceship
(blimp/whatever), does this change things?
I want the overall ambient-lit feeling that the point-light destroys, so I
am currently thinking of not using a point light unless absolutely
necessary.
Well, I could have a giant 100x100 jittered area light, but I'd like to
still be alive when it's done rendering.
"Xplo Eristotle" <xpl### [at] infomagicnet> wrote in message
news:406b28d9@news.povray.org...
> Bryan Valencia wrote:
>
> > I'm trying an outside scene on a cloudy day... it's the grass scene I
have
> > been posting.
> >
> > But the sky_sphere is always beautifully lit, while the rest of the
scene is
> > essentially black.
> >
> > Here are my settings, what's wrong?
> > global_settings {
> > assumed_gamma .8
> > ambient_light rgb .3
> >
> > radiosity {
> > pretrace_start 0.08
> > pretrace_end 0.01
> > count 500
> >
> > nearest_count 10
> > error_bound 0.02
> > recursion_limit 1
> >
> > low_error_factor 0.2
> > gray_threshold 0.0
> > minimum_reuse 0.015
> > brightness 1
> >
> > adc_bailout 0.01/2
> > }
>
> I'm going to go ahead and partly disagree with everyone here... ;D
>
> First, the ambient_light global setting doesn't set a default ambient
> finish (that's what #default is for); it sets an ambient multiplier. So
> if you're using ambient finishes ANYWHERE in your scene, they will be
> multiplied by .3. If this is affecting your sky_sphere, that would be
> the cause of your problem.
>
> Second, your count is way too high for an outdoor scene with a large
> open sky; you're wasting a lot of cycles on quality that you probably
> can't see. Try using 100 or less (30 would be plenty for test renders)
> and don't increase it unless artifacting is a problem with the settings
> you're using for the final render.
>
> Likewise, your error_bound is way too low for most outdoor scenes;
> pretty much anything below .3 or so is only useful if you want really
> detailed radiosity shadows. Try a setting of .5 or so.
>
> Your low_error_factor can probably be set to 1, especially if you decide
> to use a smaller error_bound. (Go look it up.)
>
> Some people on these groups will recommend a ridiculously high
> recursion_limit. Don't listen to them, they're fools. Most outdoor
> scenes with wide open skies can get by with a recursion_limit of 1;
> indoor scenes will usually be fine with a recursion_limit of 2. The
> difference between 2 and 3 in most scenes is nearly invisible, and
> higher settings are useless for anything except *very* indirect
> lighting.. and even then, you'd probably want 16-bit output and
> post-processing to make any use of the data.
>
> -Xplo
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