Peter Popov wrote:
> 
> On Mon, 26 Jul 1999 01:55:17 -0700, Ken <tyl### [at] pacbellnet> wrote:
> >> Replacing the spheres with the equivalent blob (of threshold 0.0001 or
> >> similar) will result in a much faster and smoother render, and you
> >> won't need to set max_trace_level too high. (You might need the
> >> 'sturm' keyword if there're a lot of elements, but that's all.) I have
> >> too overlooked this method in the past until Chris Colefax opened my
> >> eyes.
> >>
> >> Peter Popov
> >> ICQ: 15002700
> >
> >Why would this be ?
> 
> I didn't believe it either before I did the tests. First of all,
> multiple containers for multiple media proved a lot faster and
> smoother than multiple media in a single container. The reason is
> that, as the media are better enclosed each in its own container, a)
> fewer unnecessary calculations are performed and b) media intervals
> are closer together. Or, if we choose a container that's fast and
> tightly fitting the media, then it's ok too. With that said, there are
> three ways to go:
> 
> Union of spheres - fast, but has the problem of the high
> max_trace_level needed. Also, if the spheres are closely packed, it
> gets really slow. I think the reason is that every time the ray
> enters/leaves a sphere and leaves/enters another, that segment of it
> gets media sampled. Imagine what happens with 150 closely packed
> spheres.
> 
> Merge of spheres - the problems typical for the union of spheres are
> avoided, but merge is really slow as is.
> 
> Blob - the fastest of all three due to the bounding hierarchy and it
> also avoids the problems that an union of spheres has. Also, each
> element gets its media sampled separately (or so it seems) and this
> yields a smoother image.
> 
> Peter Popov
> ICQ: 15002700

 Then as I understand it Pov will treat the blob method as a single blob
entity with multiple cells as opposed to sphere which it must treat as
multiple entities. Yes ?

-- 
Ken Tyler
  
mailto://tylereng@pacbell.net
http://home.pacbell.net/tylereng/links.htm

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