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

[Greg Ward]

Implementing displacement maps in Radiance would be extremely 
difficult, I believe.  You have to change from a geometric intersection 
technique to a "proximity" intersection technique for displaced 
surfaces.  I have no idea what form this code would take, or how it 
would work.  It seems to me that it would require major overhauls of 
both the octree generator and the ray tracing engine.  I don't have 
time for it, nor have I the need for such a facility.  Radiance is 
designed for architectural models, and the more exotic renderings are 
better left to Maya and Renderman, in my opinion.

-Greg

> From: "Lars O. Grobe" <grobe@gmx.net>
> Date: January 28, 2004 3:49:05 AM PST
>
> Hi list!
>
> Once again a question about texturing a surface. In radiance, I know 
> about two ways putting color modification (pattern) or / and normal 
> modification (texture) on a surface to achieve a structured 
> appearance. Besides, brdf-modifiers allow to implement the reflection 
> effects of more complicated surfaces.
>
> However, if I have surfaces with effects caused by their 
> (micro-)structure, I get into difficulties. Radiance does not have 
> something like displacement maps, so the effects from geometry can 
> only be achieved by modeling the surface. I have been thinking a while 
> about how to get the appearance of a mosaic for example, which conists 
> of a layer of gold, a piece of glass in front of it, and which has 
> it's effect when seen from a distance because of the specular 
> reflections, the different layers and the irregularities in the 
> overall surface. Another example might be the well-known tennis-ball, 
> which can be rendered in radiance only by entering the geometries as 
> instances. However, this example hass afaik less complicated 
> reflection properties, e.g. the specular reflection is not that 
> important. There are other known examples for textures with important 
> geometric details, of course, e.g. textiles.
>
> Is there a way now to apply a geometry (in the radiance software 
> handled like an instance for memory effectiveness) as a texture? It 
> would be much more convenient to apply such a 3d-texture by using the 
> tex-modifiers to an existing surface than writing scripts to place 
> these instances following an imaginary surface. Did anybody think 
> about doing something like that with radiance, or are there reasons 
> why one should not even try that?
>
> CU, Lars.