In article <3edb8f1d@news.povray.org>,
 "Ray Gardener" <ray### [at] daylongraphicscom> wrote:

> Sorry for the confusion. For my purposes,
> I don't require all primitives, at least in
> the short to mid-term. Further along, it
> would be desirable to have as many POV
> primitives supported as possible.

What *are* your purposes? You still haven't explained this.


> I need the "lots of shapes" capability to implement shaders,

What do shaders have to do with the number of shapes?


> For shapes like hair strands and grass blades,
> however, supporting a spline (rope?) primitive
> should be done.

And what does this have to do with scanlining?


> I also don't see how an isosurface would
> be able to plant lots of trees or independant
> rocks on the terrain and maintain the
> same memory/rendering performance. If I
> was limited to raytracing, I would definitely
> brush up on isosurfaces, but otherwise...

Simple: Make a few dozen variations of tree meshes and plant a few tens 
of thousands (or more if you like) on the landscape. Blobs and 
isosurfaces can make good rocks, or you could use meshes for those too. 
And when viewed from a sufficient distance, a noisy isosurface can make 
a good bush.


> Like I mentioned, I think I have to try
> a prototype scanline implementation in POV to
> see how it goes. The jury is kind of out
> on conclusions just yet, and I don't

I haven't seen anyone but you suggest this is a good idea. Personally, I 
agree with Thorsten: adding scanline rendering to POV-Ray is silly and 
not that useful.


> want to endorse anything until I have
> accurate benchmarks. By Mr. Froehlich's
> own admission, raytracing speed doesn't
> compete with scanlining until you have
> billions of objects, so there's definitely
> room for exploration under that limit.

That's not what he said. Scanlining can compete with rendering triangles 
when memory is limited for the data, but you're ignoring other 
primitives. Your only reason given for thinking scanline would be better 
is an old paper for a computer system vastly different from modern 
computers, and your messages show extremely poor understanding of 
optimization.

Basically, POV doesn't need it, can't really benefit from it, it would 
be extremely limited compared to the raytracer, and it would be a huge 
amount of work to implement. You've given memory use as one reason, but 
raytracing can be optimized similarly. The fact that POV doesn't 
currently use these doesn't mean it never will. Speed as another, but 
you haven't compared a scanline rendering with an analogous raytracing. 
The speed advantages of scanlining are much less once you include all 
the work to make it do what raytracing does automatically. You've used 
video games as an example...POV isn't a video game, it is designed under 
entirely different constraints. If you want a preview, a much simpler 
and more effective solution would be an OpenGL preview.

-- 
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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