Christoph Hormann wrote:

> Renderman is using scanline rendering techniques, this has nothing to do 
> here.

Renderman is an interface, not an implementation, so it is not using any 
rendering techniques at all. There are a lot of Renderman 
implementations that use ray-tracing.

The REYES algorithm "dices" the primitives into a micropolygon grid - 
POV-Ray tesselates into a triangle mesh (I am talking about bicubic 
patches only - and I assume that, if they'll be implemented somday, 
NURBS and SDS will work the same way).

So there's no real difference in how parametric surfaces are being handled.

REYES applies displacement to the micropolygon grid, and POV-Ray could 
apply displacements to the tesselated triangle mesh.

 > And there of course is no self shadowing in the image you used as
 > example.

That's right... bad example. But it would slef shadow if shadows were 
turned on :-)

> I'd suggest you reread what i wrote.  This remark shows you have 
> completely misunderstood it.

Hmmm...
Christoph Hormann wrote:
 >Why would you want to do this if it is a mesh anyway and you could 
 >displace the mesh (any mesh, not just patches)?

Reread. Maybe I misunderstand. How would you displace a nurbs or patch mesh?

 >What would be interesting is support for adaptive render time 
 >subdivision of meshes with displacement.

That's exactly what I was trying to say - sorry if the term 
"tesselating" was wrong (I'm not a native english speaker), still I feel 
that it is more correct than "subdivision". You can subdivide a polygon 
mesh to get a finer polygon-mesh (that's how SDS works), but subdividing 
a patch will only yield more patches...

-Sascha

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