Kari Kivisalo wrote:

> Here is my 1st try with the simulation just to see if
> it would benefit from tonal range modification. Maybe
> later.


Pretty good !  As I said earlier, commercial packages have
built-in exposure/tonal correction, and it's just right to
process the image.

Too bad it isn't possible to turn reflection off for
radiosity samples.  Commercial packages does that,
and thus gain much speed without noticeable difference.

Fabien.

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"Kari Kivisalo" <ray### [at] engineercom> wrote in message
news:3C1BBA3A.EA4AD09E@engineer.com...
>
> Where is the sun supposed to be?
You can guess it from the 3DMAX screen shot on the web page. Some where
near <-12.0, 28.0, 48.0> (the previous post had a wrong x value).

Ari-Matti

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"Fabien Mosen" <fab### [at] skynetbe> wrote in message
news:3C1### [at] skynetbe...
> Too bad it isn't possible to turn reflection off for
> radiosity samples.  Commercial packages does that,
> and thus gain much speed without noticeable difference.

http://www.students.tut.fi/~leppane6/pics/sibenik_25m.jpg
http://www.students.tut.fi/~leppane6/pics/sibenik_20m.jpg

These aren't good looking, just testing this trick.
The first is a one trace image (25min ??s). The second is traced in to
steps. First commented out reflections and added save_file to the radiosity
block. After the trace (19min 27s) reflections were uncommented and in the
radiosity block save_file was replaced with load_file, pretrace_start and
pretrace_end were set to 1 and added always_sample off. This trace took 1min
16s, total time 20min 43s.
They look quite the same and later saved about 4 minutes. Looks like that in
the 20 minute version the red bleeds more.

Ari-Matti

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ingo wrote:
>
> There is sunpos.inc in the 3.5 distribution.

Maybe I should read the manual again :) 

Anyway, I need at least 256MB more RAM to be able to render this
one with good rad settings. I'll try again in January.


_____________
Kari Kivisalo

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Ari-Matti Leppanen wrote:

> These aren't good looking, just testing this trick.


Is what you did *really* equivalent to bypassing the reflection in 
radiance samples ?

There is one thing I'm absolutely sure of : LightScape, which renderings
are found great by most everyone, *doesn't* account reflection for it's
radiance solution calculation.  In fact, due to it's algorithm, it 
*can't* !  Energy transfers can't take specular reflection into account.
Also, please note it doesn't even take *textures* in account (for the
same reason), only a plain diffuse color.  Finally, it doesn't render
bumps, but that's another issue.

As far as I could gather information, other radiance engines, 
monte-carlo/bidirectional/photons/... based, also *don't* take specular
reflection into account.

Fabien.

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"Fabien Mosen" <fab### [at] skynetbe> wrote in message
news:3C1### [at] skynetbe...
> Ari-Matti Leppanen wrote:
>
> > These aren't good looking, just testing this trick.
>
>
> Is what you did *really* equivalent to bypassing the reflection in
> radiance samples ?
>

The documentations says: 6.11.11.1 "..provides a way to replace the last
term - the constant ambient light value - with a light level which is based
on what surfaces are nearby..".
By that I would say that reflections don't affect the result so it's *not
really* equivalent.
Then speed difference is probably from the fact that always_sample is off in
the second case. I should check if there's a difference when it's on.

Ari-Matti

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Fabien Mosen wrote:
>
> Also, please note it doesn't even take *textures* in account (for the
> same reason), only a plain diffuse color. Finally, it doesn't render
> bumps, but that's another issue.

So this is why those Lightscape entrys look cartoony!


_____________
Kari Kivisalo

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Ari-Matti Leppanen wrote:

> The documentations says: 6.11.11.1 "..provides a way to replace the last
> term - the constant ambient light value - with a light level which is based
> on what surfaces are nearby..".


Which is the basic principle of any radiance engine.


> By that I would say that reflections don't affect the result so it's *not
> really* equivalent.


It does.  POV-Ray takes reflection of surfaces into account when taking
radiance samples.  I've done a test scene to check that.  IMO, we 
should, at least, have an option to disable it.

Fabien.

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Kari Kivisalo wrote:

> So this is why those Lightscape entrys look cartoony!


Yep !  The engine is pretty incomplete, texture-wise.  No bumps, not 
even slightly complex procedural texturing.

However, on has to admit the obvious quality of light in these images.

Fabien.

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Dynamic range compression test with half resolution
image and radiosity solution that fits in 256MB RAM.
Sun position from the sunpos macro. I used count 1200
and it seems it's not enough. The noise may also result
from my poor choice of clipping intensity.

http://www.pp.htv.fi/kkivisal/church2.jpg


_____________
Kari Kivisalo

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