"John Pallett" wrote:
> Hi guys -
>
> Some more notes -
>
> I was surrounding my entire scene with a gigantic white sphere, not creating
> a 'spherical sun'.  The problem, as it turns out, was that the light wasn't
> getting scattered around the room enough for it to properly simulate
> sunlight coming in a window (which scatters all over the room).  So the
> scene consisted of:
>
> - A huge white sphere, ambient 0.5
> - A parallel white light (sunlight) (parallel lighting for the sun is good
> enough for our purposes)
> - A room with a window, all materials set to (ambient 0, diffuse 0.9) so
> that they aren't emitting light into the scene
> - My camera inside the room
>
> Thanks to everyone for suggestions thus far.  The missing ingredient seems
> to have been media, which can be used to scatter light.  What I am doing now
> is using media inside my rooms to scatter the sunlight as it comes in the
> window and as it bounces around the room.  Very subtle scattering gives me
> great results.
>
> I'll post images to PBI once I get something put together that demonstrates
> the problem clearly.
>
> Can anyone suggest another way to solve the problem of having the light
> coming in the window scatter around the room appropriately?  Note that my
> camera points TOWARDS the window, so making the window's wall invisible is
> not an option.

Ah. Too bad. Then you have to:
1) Raise the count to appropriate value.
2) Raise the recursion limit to appropriate value (3).
3) Raise the brightness to appropriate value (2.5, 3 or even more)
4) Be very patient.

Otherwise you could put a huge area_light right where the window is. This, with just
a bit of tweaking, should give you very soft shadows which, together with just a bit
of radiosity, might look nice nonetheless. This can be very slow too.

Anyway ambient 0.5 is pretty low for a skysphere. Use a real sky_sphere with a
gradient from white (bright white: rgb 1.25) to sky blue.

--
Jonathan.

Post a reply to this message

So no value in using scattering media to help "scatter" the sunlight around
the room...?

JP

"JRG" <jrg### [at] hotmailcom> wrote in message
news:3d41b4f1@news.povray.org...
> "John Pallett" wrote:
> > Hi guys -
> >
> > Some more notes -
> >
> > I was surrounding my entire scene with a gigantic white sphere, not
creating
> > a 'spherical sun'.  The problem, as it turns out, was that the light
wasn't
> > getting scattered around the room enough for it to properly simulate
> > sunlight coming in a window (which scatters all over the room).  So the
> > scene consisted of:
> >
> > - A huge white sphere, ambient 0.5
> > - A parallel white light (sunlight) (parallel lighting for the sun is
good
> > enough for our purposes)
> > - A room with a window, all materials set to (ambient 0, diffuse 0.9) so
> > that they aren't emitting light into the scene
> > - My camera inside the room
> >
> > Thanks to everyone for suggestions thus far.  The missing ingredient
seems
> > to have been media, which can be used to scatter light.  What I am doing
now
> > is using media inside my rooms to scatter the sunlight as it comes in
the
> > window and as it bounces around the room.  Very subtle scattering gives
me
> > great results.
> >
> > I'll post images to PBI once I get something put together that
demonstrates
> > the problem clearly.
> >
> > Can anyone suggest another way to solve the problem of having the light
> > coming in the window scatter around the room appropriately?  Note that
my
> > camera points TOWARDS the window, so making the window's wall invisible
is
> > not an option.
>
> Ah. Too bad. Then you have to:
> 1) Raise the count to appropriate value.
> 2) Raise the recursion limit to appropriate value (3).
> 3) Raise the brightness to appropriate value (2.5, 3 or even more)
> 4) Be very patient.
>
> Otherwise you could put a huge area_light right where the window is. This,
with just
> a bit of tweaking, should give you very soft shadows which, together with
just a bit
> of radiosity, might look nice nonetheless. This can be very slow too.
>
> Anyway ambient 0.5 is pretty low for a skysphere. Use a real sky_sphere
with a
> gradient from white (bright white: rgb 1.25) to sky blue.
>
> --
> Jonathan.
>
>
>
>

Post a reply to this message

I have (had?) a complete animation with this church scene. My bro almost
couldn't believe it was done using computer(s). Absolutely stunning.

Post a reply to this message

"John Pallett" wrote:
> So no value in using scattering media to help "scatter" the sunlight around
> the room...?

Although "media on" in the radiosity block makes media affect radiosity, I doubt it
would be of any help here.


--
Jonathan.

Post a reply to this message

Not sure about that, remember the "god's fingers" situation when light
crawls through small openings in dusty/smoky areas?

Post a reply to this message

Some good news actually regarding scattering media - I'm getting some good
results from this.

I tried adding a very simple scattering media to my room and it made a huge
difference - even without any emissive characteristics, the scattering
effect caused rays to bounce more or less as I'd expect sunlight to interact
with my room.  It's almost as if the 'scattering' of a single radiosity ray
simulates the effect of the sunlight bouncing around the room several times.

Unfortunately it's very tweaky - small changes in radiosity settings mean
you have to modify the media - but I'm still working on it.  The good news
is that using media, I can get good results in much less time than by
cranking up my radiosity settings.  I may not be able to get a reliable
framework out of it - but I will let you know if I do.

JP

"JRG" <jrg### [at] hotmailcom> wrote in message
news:3d41d1cb$1@news.povray.org...
> "John Pallett" wrote:
> > So no value in using scattering media to help "scatter" the sunlight
around
> > the room...?
>
> Although "media on" in the radiosity block makes media affect radiosity, I
doubt it
> would be of any help here.
>
>
> --
> Jonathan.
>
>
>
>

Post a reply to this message

In article <3d41d1fb$1@news.povray.org>,
 "Apache" <apa### [at] yahoocom> wrote:

> Not sure about that, remember the "god's fingers" situation when light
> crawls through small openings in dusty/smoky areas?

That is not due to beam divergence, it would happen with truely parallel 
light. It is caused by perspective: the rays come through the clouds at 
a distance and pass to each side. If the sun was close enough for 
divergence to be visible, there probably wouldn't be clouds and you 
wouldn't be there to see it.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

Post a reply to this message

What else can be used to simulate the adaption the eye makes in 
low-light situations?

Christopher James Huff wrote:

> In article <3D4### [at] caltelcom>,
>  Samuel Benge <sbe### [at] caltelcom> wrote:
> 
> 
>>Try setting assumed_gamma to somthing very low, like 1 or 0.5. This will 
>>brighten everything up, hopfully simulating the natural adjustment our 
>>eyes make in low-light situations.
>>
> 
> Very low? 1 is the recommended value..."For new scenes, you should use 
> an assumed gamma value of 1.0 as this models how light appears in the 
> real world more realistically."
> 
> 


-- 
Samuel Benge

sbe### [at] caltelcom

Post a reply to this message

In article <3D4### [at] caltelcom>,
 Samuel Benge <sbe### [at] caltelcom> wrote:

> What else can be used to simulate the adaption the eye makes in 
> low-light situations?

You could use an external program to process the contrast of the image 
(or do it in POV using functions, see the recent find_edges images for 
an example), or you could use a patch that allows you to adjust the 
dynamic range of the image. The raw_image and curves patches of MegaPOV 
could be used for this.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

Post a reply to this message

On Fri, 26 Jul 2002 18:47:15 -0500, Christopher James Huff wrote:
> In article <3d41d1fb$1@news.povray.org>,
>  "Apache" <apa### [at] yahoocom> wrote:
> 
>> Not sure about that, remember the "god's fingers" situation when light
>> crawls through small openings in dusty/smoky areas?
> 
> That is not due to beam divergence, it would happen with truely parallel 
> light. It is caused by perspective: the rays come through the clouds at 
> a distance and pass to each side. If the sun was close enough for 

And in fact, on particularly good days you can see convergence on the 
other side of the sky as well; APOD has had a few examples of this 
phenomenon. 

-- 
#macro R(L P)sphere{L F}cylinder{L P F}#end#macro P(V)merge{R(z+a z)R(-z a-z)R(a
-z-z-z a+z)torus{1F clipped_by{plane{a 0}}}translate V}#end#macro Z(a F T)merge{
P(z+a)P(z-a)R(-z-z-x a)pigment{rgbf 1}hollow interior{media{emission 3-T}}}#end 
Z(-x-x.2x)camera{location z*-10rotate x*90normal{bumps.02scale.05}}

Post a reply to this message