Hugo wrote:
> 
> [...]
> 
> Please understand the concept: I have skipped all "light_source"
> commands because they are poor fakes. Instead I try to use a realistic
> enviroment. This means, I set up any object and let it's ambient value
> determine how much light it emits with radiosity. Then I (as with the
> sphere in the attached pictures) use blurred reflection to get specular
> highlights on light-absorbing objects.. This is the realistic way of
> making highlights, instead of specular / blinn / phong keywords.
> 

I doubt there is much use in this, since a lot of other things are still
fake.  At least you would have to use photons too then (of course they
only work with light sources).

radiosity only effects the diffuse lighting of the scene, using extremely
high ambient objects is not necessarily more realistic than light
sources.  

> I managed to balance these 3 things well:
> 
> (1) The "brightness" value in radiosity global settings.
> (2) The strength of ambient values (going much over 1) to emit light.
> (3) The diffuse & reflection keywords on light-receiving objects.
> 
> But the problem: I experimented with the best radiosity-settings I could
> think out, and find.. With recursion_limit set to 1, results look pretty
> good; actually very similar to ordinary light_sources but with some
> plusses: a WHOLE object emit light, specular reflections are realistic,
> ans render times acceptable.

If they are while you use blurred reflection, your radiosity settings are
probably not very high quality.  The problems in the second pict look very
much like ordinary artefacts you could eliminate by increasing count and
tweaking some other values.  

> 
> BUT the light doesn't bounce off, more than once. It goes from the light
> sources (the ambient objects) to the first receiving object, and no
> further. So a shadow will still be completely dark, if there is no
> direct light source on the other side.
> 
> The solution is obvious: Raise recursion_limit to 2, but I got stuck
> here, as things immediately look awful, no matter what I do.. Does
> anyone have an idea WHY, and is there a solution??  I would be
> interested.. Unfortunately, render times on the awful picture was very
> high.. I tried to further raise radiosity quality to get rid of the
> artifacts, and had to break a rendering after 12 hours, not finished,
> and the result didn't look any better.
> 

That's what you have to expect.  Try using good old faked highlights and
things will be much faster.  Using light sources instead of pure rad
lighting usually also produces less artefacts.  

> So help me! Help all of us, to get realistic lighting! And please don't
> say radiosity is great, until these big problems are solved.
> 

You always have to remember that radiosity is not a all purpose fool proof
solution for all lighting problems.  I think it can help to achieve really
good results, but of course there are problems and disadvantages like slow
rendering, artefacts and like all other approximations (in fact everything
in Povray is faked), it has it's serious limits.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

Post a reply to this message