"clipka" <nomail@nomail> wrote:
> "Reactor" <rea### [at] hotmailcom> wrote:
> > Well... basically, when you start to run into the 1600 count limit or the count
> > vs patience limit, I've found that some scenes can actually be made to work
> > with a lower count than usual by lengthening the pretrace step and dropping the
> > error bound very low.  Since one usually sees splotches when the count is too
> > low for a given error_bound, if the error_bound is dropped low enough, the
> > splotches become very small and distributed such that the shadows and shading
> > start becoming reasonably accurate again.
> > Depending on the scene, this method can work fairly well.  I have had some
> > degree of success on scenes that are indoors and involve sharper shadows and
> > rapid changes of light.  Outdoor, architectural scenes involving slower changes
> > of light and softer shadows seem to do better with the usual approach.
>
> I see... so what you're basically doing is "de-bundling" the sample rays.
>
> Theoretically this should be somewhat slower, as you probably use the same
> number of sample rays (total, not per sample), and just distribute them more
> evenly across the whole scene, so the lookup will be slowed down.
>
> However, I can also see how this might smoothen the look of the scene.
>

It doesn't smooth it much, actually.  I use it for sharp edges and small things
that a larger error bound would miss (i.e. radiosity is largely unaffected by
the addition or removal of the object).  In those cases, a small count of very
accurately, possibly widely spaced samples is more visually correct.  So far,
it is turning the door into a diffraction grating :(

I have noticed that an error_bound greater than 0.075 leads to the light
"seeping" through the walls.  Attached is an image rendered under
3.6.1.icl8win32  with the following radiosity block:

  radiosity {
    pretrace_start  64/image_width
    pretrace_end     1/image_width
    count 25
    nearest_count 20
    error_bound 0.05
    recursion_limit 4
    low_error_factor 0.5
    gray_threshold 0
    minimum_reuse 0.01
    brightness 1.0
    adc_bailout 0.01
    always_sample on
  }
  #end



I am still testing under MegaPov, but so far, this scene looks like it will
require a very high count, which is what I was hoping to avoid.

-Reactor

Post a reply to this message

Attachments:
Download 'the_secret.jpg' (26 KB)

Preview of image 'the_secret.jpg'