Kenneth nous apporta ses lumieres en ce 10/08/2006 17:18:
>>> Alain <ele### [at] netscapenet> wrote:
> 
>>>> Shifting this "may" help you getting rid of some artefacts near corners like
>>>> dark spots along inside corners.
>>> Shifting it up ot down?  Is it better to use a higher value for this or a
>>> lower value?
>> Equivalent. You only want the pretrace sampling to shift place so that they miss
>> the problem pixels. It's also advisable to move the camera a very small amount,
>> like +/-0.000001 unit.
> 
> Do you mean, shifting the camera BETWEEN the pretrace steps? If so, how
> is that done?
> 
> Ken W
> 
> 
Not during the pretrace. Before you start the rendering. There are some cases 
where a radiosity sampling falls exactly on an internal corner. In those cases, 
the sampling can look behind a wall for example, taking information from a 
totaly dark area, leading to dark spots along the corner.
Changing pretrace_start or moving the camera very slightly can cause the problem 
sampling to miss the critical points.

-- 
Alain
-------------------------------------------------
Wouldn't it be nice if whenever we messed up our life we could simply press 
'Ctrl Alt Delete' and start all over?

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Kenneth nous apporta ses lumieres en ce 10/08/2006 16:18:
> "Samuel Benge" <stb### [at] hotmailcom> wrote:
>> Hi Ken. Are you the same Ken who once ran a big list of graphics links?
> 
> Nope, never did. Sorry!
>>
>> If I may give you some settings I always use for radiosity. Try these alone...
>>
> 
> I'll give them a whirl, and report back with the results.  Thanks.
>> The error_bound should be low for better shadows. This is one of the most
>> important settings. error_bound and count together should be modified
>> before anything else.
> 
> Yes, I've been wondering about that.  It seems that count
> ISN'T the FIRST  thing to modify (given defaults
> for everything else.) Not much visual
> difference between low and high values, without modifying other things "in
> step" as well. Thanks for the tip.
>> In addition to these things, you should use a bright, fading (fade_power 2)
>> light inside the sphere instead of just making the sphere very bright. An
>> area_light (with orient and circular flags added) works well for this. The
>> sphere should be given the no_shadow flag to let the light shine through.
> 
> Alas, I was *hoping* I could light this scene realistically just by using a
> pure, small ambient "light source," but I do understand that the radiosity
> equations (and/or just the default values) were made to be used with
> ACTUAL light sources. I may ultimately have to do as you suggest.  Haven't
> given up yet, though! ;-)
> 
> Let me ask a very basic question:
> 1)  Is it ALWAYS better --that is, more realistic and of higher quality--to
> use the highest count possible and a very low error_bound value? (Assuming
> that the resulting l*o*n*g render time is unimportant.)
> 
> Ken W.
> 
> 
> 
> 
> 
> 
You can have realy good lighting using only radiosity, but you get beter result 
if you use relatively large ambient lights.

-- 
Alain
-------------------------------------------------
Everybody should believe in something: I believe I'll have another drink.

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Kenneth wrote:
> Sorry, I may have described things the wrong way.  In my scene, it *seems*
> that there should be MORE color spill onto the ceiling, from the
> saturated-color walls. But then again, the tall (distant) box shape seems
> to show quite good color spill from the red wall.  So perhaps I'm looking
> for an effect that really shouldn't be there. Difficult to tell!

   Then I think you are expecting too much spill, more than normal for 
regular surfaces.

> [...] A higher nearest_count DOES radically improve
> things--but from what I've seen, it appears to make shadows less defined,
> sort of smoothing them out. Am I mistaken about that? Is it interacting
> with "something else" that I should change?

   Yes, with every other parameter!!! :) But I usually also raise 
error_bound and that compensates the effect.

> I'm still trying to understand this "bounce" idea. But you're right, higher
> recursion_limit values seem to have less and less of an effect. I've
> settled on 3. Is it correct to assume that the more bounces, the more the
> various radiosity-created colors in the scene blend together and become
> MORE muted? If so, it sounds like something to be avoided (?) As you can
> see, I'm really struggling with these concepts!

   The more bounces, more realistic is the radiosity, as in reality 
there are infinite bounces. But it's only useful with maze-like 
situations. I think you should only use the number of bounces needed 
just to light all the visible parts of the scene, no more.

--
Jaime

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Alain <ele### [at] netscapenet> wrote:

> You can have realy good lighting using only radiosity, but you get beter result
> if you use relatively large ambient lights.
>
> --

Yes, that has been my experience as well. Making my single ambient 1 light
just two or three times larger greatly improves the "realistic" look of the
bounced radiosity.  I think that I might be giving POV a somewhat *extreme
situation* to deal with, by making my single light sphere so small. In
"normal" radiosity scenes that I've done, using a sky_sphere
and several actual light sources, it is MUCH easier to get
good results.

Ken

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Kenneth nous apporta ses lumieres en ce 12/08/2006 17:28:
> Alain <ele### [at] netscapenet> wrote:
> 
>> You can have realy good lighting using only radiosity, but you get beter result
>> if you use relatively large ambient lights.
>>
>> --
> 
> Yes, that has been my experience as well. Making my single ambient 1 light
> just two or three times larger greatly improves the "realistic" look of the
> bounced radiosity.  I think that I might be giving POV a somewhat *extreme
> situation* to deal with, by making my single light sphere so small. In
> "normal" radiosity scenes that I've done, using a sky_sphere
> and several actual light sources, it is MUCH easier to get
> good results.
> 
> Ken
> 
> 
> 
> 
Small ambient light mean more chance for ALL samplings from any sampling area to 
miss it, resulting in dark patches in areas that should be lighted. If you rely 
on a small ambient light, you must use a high count value to increase your 
chance that any sampling will actualy hit that small object.

-- 
Alain
-------------------------------------------------
OFFICE ARITHMETIC
Smart boss + smart employee = profit
Smart boss + dumb employee = production
Dumb boss + smart employee = promotion
Dumb boss + dumb employee = overtime

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Alain <ele### [at] netscapenet> wrote:
> Kenneth nous apporta ses lumieres en ce 12/08/2006 17:28:
> > Alain <ele### [at] netscapenet> wrote:

> Small ambient light mean more chance for ALL samplings from any sampling area to
> miss it, resulting in dark patches in areas that should be lighted. If you rely
> on a small ambient light, you must use a high count value to increase your
> chance that any sampling will actualy hit that small object.

That's a good analysis of something quite important that I
didn't realize. Thanks!

Ken

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