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

[Rob Guglielmetti]

Hello all.  Some of you know me, many do not.  But I have 
been experimenting with Radiance lately.  Thanks to Greg 
who tipped me off to the power of OS X (and his pre-
compiled binaries for 3.4).  I struggled with LINUX many 
times, but never got a totally functional system; I was 
rpicting all over the place after a week on OS X.  =8-)

Anyway, now that I'm getting a feel for how the various 
programs work together, I have gone back and am now 
reading the old Radiance Digests.  This has been helpful. 
Those things read like a "Who's Who in the Radiance 
Community".  And to see many of the gurus, with more 
questions than answers, makes me feel like someday I 
may get my head around all of this stuff!  Of course, many 
of those messages are eight years old.  Hmmm...

Enough rambling.  Questions:

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).  

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?  

Greg in one of the digests said windows can be modelled 
using a single plane of glass.  (I'm used to Lightscape's 
requirement of two opposite-facing planes, lest you get 
refraction errors in a raytrace.)  Does this hold true for the 
rest of the building?  IOW, a simple room can be modelled 
with a single genbox?  I have been creating an inner 
room and an outer "shell".  Again, this may be my 
Lightscape logic getting in the way of things here.  Of 
course for detailed renderings you *have* to model the 
wall thickness, but for daylighting analysis, would a single 
box (with windows of course) suffice?  In Lightscape you 
would get "light leaks" around the corners of the interior 
as sunlight affected the vertices unless you enclosed the 
interior with an outer shell.

Re: skies.  Gensky (directed by George Mischler's radout) 
creates a description of the sky & ground luminance, and 
creates two colored hemispheres.  I have seen some 
special sky textures available for mapping to a sphere for 
more realistic environments.  How do these work?  Are 
they transparent placeholders, which merely display a 
picture of the sky but allow the sun & sky luminance to 
"pass through", or do they actually modulate the sky 
luminance as a function of the chromacity of the pixels in 
the sky image?

I have been using George Mischler's radout to bring 
geometry from AutoCAD to radiance.  But there doesn't 
seem to be a way to handle blocks.  It would be great if 
there was a way to substitute autocad blocks for 
instanced rad files!  One could export the blocks as 
separate rad files, but is there a way to take a series of 
insertion point coordinates and build a rad file that 
instances the "block" rad file at those 
coords/orientations?  That seems to be the key to being 
able to rapidly change scenes, and stay accurate.  Anyone 
doing this type of thing already?

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?  I know you can feed 
rtrace the points, but I'm interested in a way to have 
autocad export the information rather than me figure out 
the points manually.  I like to draw the stuff and have 
CAD keep track of all the math, ya know?

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).  

Paul Bourke offers some great tree examples.  Again, 
does anyone have other blocks they are willing to share 
(vegetation, furniture, you name it)??  =8-)

Paul also has a benchmark page: 
http://astronomy.swin.edu.au/~pbourke/radiance |
/benchrad/

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?  Makes Apple's ad copy 
about the "Velocity engine" in the G4 seem like a load of 
bunk (which I suspected in the first place).   Don't get me 
wrong, I love this Mac.  But it seems that when I finally 
am ready to do production work with Radiance I'm gonna 
have to learn LINUX once and for all.  The cheapest cpu 
cycles are with homebuilt PCs, so it seems that's the way 
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? 

Woah.  That got long in a hurry.  I'll leave it at that for 
now.  More questions to follow hopefully.  I'd greatly 
appreciate any responses to my inquiries above.  


         ====================
 Rob Guglielmetti <rpg777@earthlink.net>
    http://home.earthlink.net/~rpg777