[Radiance-general] Too many questions to fit in the subject

[Peter Apian-Bennewitz]

Hi Rob,

> Philip Thompson, way back in '94, inquired about the
> ability to show surface normal orientation in rview.  Was
> this ever developed?  My frame of reference is Lightscape,
> which has been excellent in this regard.  Surface normals
> can be interractively viewed, and backfaces are displayed
> in a garish green color.  Incorrectly oriented surfaces can
> be flipped with a click of a button.  It was only after my
> initial experiments that I learned surface normal
> orientation is a non-issue in Radiance (excepting windows
> via mkillum).
IMHO, the only real non-trivial problem with incorrectly oriented
surfaces happens with solid glass (=dielectric) objects. If the CAD
spills out polygons with quasi-random orientation (AutoCAD 12 caused me
some temporary headaches years back), hand tweaking the orientations is
not an option. Problems with orientation of glow and spotlight surfaces
are typically easier to hand-tweak. All other surfaces, as you know,
don't care for orientation. 

> Failing rview, what other geometry previewers are you
> folks using?  Ole Lemming's ConRad has a useful
> previewer, that operates similarly to the "view setup"
> dialog in Lightscape.  I really think this would speed
> things along for me, the ability to interractively orbit a
> scene & check for modeling errors, normal orientation, etc,
> and most importantly, SETTING VIEWS.  THis is a real
> hassle when you have to provide vp, vd as 3D points.  Are
> there other previewers besides ConRad?
http://www.pab-opto.de/progs/rshow/rshow.html - shows surface
orientation too (when moving the mouse over surfaces and keeping the
middle (OS-X ??) button down.) come to think of it,- there's no OS-X
version available yet.

> ...
> 

> 
> Along those lines, is there a way to create a grid or really
> any series of points in autocad (via nodes, or blocks or
> whatever) and then have the coordinates of those points
> be fed to rtrace for lighting analysis? 
rshow has an option for that too
 ... 
> I found a nice collection of materials online (Kevin
> Matthews, Design Workshop).  Some of the cal files are
> missing, but many of the materials are usable.  Does
> anyone else have material & light libraries they are willing
> to share?  I'm also really interested in obtaining
> definitions of translucent materials, such as one would
> find in a light fixture (sandblasted glass, acrylic, etc).
I guess one problem with libraries is the naming. When 4 people find
"Sandblasted" in the list, they have 25 different ideas how that looks
in reality. "Lightly sandblasted" doesn't help either.
> 
...
> 
> I tried the first one and my PowerBook G4 550 rendered it
> in 582 secs, which is almost exactly three times as long as
> the render time for a 1.5 GHz P4 (see the site for more
> times).  Is it just coincidence, or is there a fairly direct
> correlation between CPU speed and render time,
> regardless of processor type? 
No way. CPU architectures (super-scalar, pipelining, cache coherence)
plus compiler optimizations de-correlate clock speed from rendering
times.

> to go.  Interestingly, there is a benchmark for a dual 2GHz
> PC, which was only 50% faster than the single 1.5 GHz.
> I'm interested in parallel processing, but this seems to
> make a case against it.  What are your experiences out
> there in the field?
I've got no experience with 2Ghz (AMD ?) dual boards, although all other
duals (PII 200MHz- PIII 1Ghz) worked as expected so far. Mem speed, disk
times (if needed, typically not so much for Radiance during rendering,
rpict does heavy I/O only at startup while reading the scene) and cache
size may slow down overall throughput.
btw: With rpict, -PP allows sharing the geometry between two rpict
programs on the same machine. Useful for large scenes.

-Peter
-- 
 pab-opto, Freiburg, Germany, www.pab-opto.de