In article <3f7dd3f1@news.povray.org>,
 "Chris Johnson" <chr### [at] chris-jcouk> wrote:

> What's the difference between using the blurred reflection code in 
> _Light_Beam_'s link and rendering an animation with a single texture 
> level on the object, and averaging the output images?

Well, that method will trace many single paths. The paths do not split 
with this method. It could possibly be used to get good results with 
fewer rays. With the usual method, most of the rays are at a fairly deep 
recursion, and don't contribute as much. The primary problem that makes 
blurred reflection slow is the exponential explosion of rays traced when 
you get multiple levels of reflection.

What you propose is similar to another raytracing algorithm I've read 
about where a single path is always traced. When a surface with 
reflection and transparency is encountered, where a conventional 
raytracer would split into two rays, just one of the paths is chosen. To 
get the pixel color, many of these samples are added together. If you 
have deep recursion and/or large numbers of samples, this can greatly 
reduce the total number of rays traced.


> I'm sure this method must have been thought of before - is there any 
> reason why it should be inferior in accuracy than using multiple 
> layers of texture?

It is inferior in accuracy, but mainly due to the fact that images have 
limited precision. You should be able to get good results in most cases, 
with fewer rays cast than in a simplistic "cast a bunch of rays" blur 
algorithm, but a smarter version of that algorithm might do even better. 
The main problem is that it is a bit awkward and inefficient to render 
whole frames and then process them together.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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