[Radiance-general] defining structured (textured) surfaces in radiance?

[Greg Ward]

Aside from the slight overlap or underlap at the edges depending on 
surface curvature, your idea is basically sound.  However, implementing 
this idea efficiently in Radiance would be a big challenge.  If we were 
to minimize code changes, we'd be using instances of some kind with 
clipping, and we'd end up with a lot of overlapping suboctrees.  Many 
on this list can tell you their headaches surrounding those if you 
haven't had enough of your own.  Getting tighter bounds on the 
instanced geometry would require some rather fundamental changes to the 
handling of octrees, and still wouldn't completely remedy the problems 
with side-by-side instances.  They just don't work that well.

Geometry as a modifier also would entail rewriting the octree 
generator, which currently ignores all surface modifiers.  I'm not sure 
how much work this would be, but I would say "more than a little."  
Unless there is some general need for this kind of rendering in 
Radiance or someone with money and/or time to spend on it, I don't see 
it happening.

-Greg

> From: "Lars O. Grobe" <grobe@gmx.net>
> Date: February 3, 2004 12:32:04 PM PST
>
> Hi Greg,
>
> I did not think that using the typical displacement map is the best 
> solution. My idea was taking a geometry as a surface modifier. The 
> basic functionality is provided by todays radiance: instances and the 
> replmarks program are doing almost what I want. If I don't replace 
> every triangle (like replmarks does) with an instance, but every face 
> of a geometry, using the uv-values to place and rotate the instance, 
> then cutting this instance at the boundaries of the face, I have a 
> 3d-texture... or am I totally wrong here?
>
> CU Lars.