In article <3eda7633@news.povray.org> , "Ray Gardener" 
<ray### [at] daylongraphicscom> wrote:

>>   Could you profundize on this? What exactly is the difference between
>> scanline rendering and raytracing which makes the former better for
>> rendering a huge amount of objects?
>
> This was answered well in Catmull et al's original
> paper on REYES in SIGGRAPH 87, but I'll explain.

You are talking about "The Reyes image rendering architecture", I guess?
And taking a four sentence paragraph that says little if anything to justify
your argument?  Lets see, well, I have to type this because the ACM digi lib
has this only scanned:

>>>
2.1. Geometric Locality.
When ray tracing arbitrary surfaces that reflect or refract, a ray in any
pixel on the screen might generate a secondary ray to any object in the
model. The object hit by the secondary ray can be determined quickly
[references omitted - trf], but that object must then be accessed from the
database. As models become more complex, the ability to access any part of
the model at any time becomes more expensive; model and texture paging can
dominate the rendering time. For this reason, we consider ray tracing
algorithms poorly suited for rendering extremely complex environments.
<<<

And this is all.  As you are aware that this was 16 years ago, a single
author's analysis, and the context of the paper is rendering feature-film
length animations?  I am not even going to start to reason here how
nonsensical it is to base your argument on this paper.

And the lengthy "argument" that follows in your post, well, you don't want
to keep the whole scene in memory and that is why you want to use a (even
"more" memory limited) 3d accelerator to draw that model?  Carefully
transmitting all the geometry and texture data over a rather slow bus for
every frame?  And as far as textures are concerned, you do know that number
of texture samples to be taken by a ray tracer grows linearly with the image
size, while for a scanline renderer is grows linearly with the polygon
number and size?

I am not going to laugh, I am surprised you didn't know better (also you
should), and I am just going to ignore the rest of this thread ... sorry!

    Thorsten

____________________________________________________
Thorsten Froehlich
e-mail: mac### [at] povrayorg

I am a member of the POV-Ray Team.
Visit POV-Ray on the web: http://mac.povray.org

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