[Radiance-general] Modeling Paradox

[Rob Guglielmetti]

Hi Jeffrey,

> 	Now that I've gotten my feet wet with
> Radiance, so to speak, I'm left with a bit of
> a paradox; Radiance has provisions to describe
> almost any conceivable geometry I could need
> in modeling buildings; however none of the export
> programs I have used take advantage of this-
> everything is turned to triangles.

What CAD program are you using?  What exporter are you using?  You have  
to understand that the basic building block of ACIS-based modeling  
programs -- when talking to other software -- is the damned triangle,  
unfortunately.  3DStudio is great at producing models with more curves  
than Pamela Anderson, but when you ask it to export that model for use  
in another application, it spews forth a zillion triangles.  It's not a  
Radiance limitation, it's an ACIS translation problem.

> There are times that this simply doesn't work;
> such as aiming failures and bad looking curves,
> and times where it's merely annoying, in that
> I wish to replace some exported geometry from
> CAD with Radiance-native geometry, but can't
> easily do so because the item I wish to replace
> is a tangle of triangles, and it's hard to discern
> it's placement from the mess within the RAD files.

AutoCAD, when used with Georg Mischler's Radout program  
(http://www.schorsch.com/download/radout/), can produce much cleaner  
models.  I use AutoCAD and 3D faces as much as possible.  When you use  
3D solids in AutoCAD, the only way to get them out of ACAD is to  
convert them to a 3DStudio mesh first, and that means triangles (and  
oftentimes, LOTS of triangles).

As for the placement of native Radiance geometry, have a look at  
replmarks (http://radsite.lbl.gov/radiance/man_html/replmarks_1.htm).   
You can use your CAD program to place (with great accuracy and  
familiarity) markers that can be easily swapped out with a .rad file or  
an octree (but don't use octrees for light sources, as I found out the  
long way  
[http://www.radiance-online.org/pipermail/radiance-general/2003-August/ 
000946.html]!)

> I can already produce renderings within
> Radiance that are much better than anything
> I've done before. However I still haven't
> found an efficient and acceptable workflow
> due to my reliance on CAD systems for generating
> geometry (and their somewhat inferior exporting
> ability).

> So again I'm bothering all of you in asking
> for two things; first off, how much & what do you
> typically model in CAD and how much do you typically
> describe within Radiance (or array, or instance)
> for a given project; and secondly, has anyone
> ever made an effort to make a 3D GUI modeler that
> uses Radiance as it's native file format?

You know what?  I've been slowly learning Radiance over the last year  
and a half, and I still don't have a real workflow, and I know that's  
my biggest problem right now (well, that and the fact that I need to  
cut down on the cholesterol).  Right now I use CAD and try to use  
3Dfaces as much as possible, export with radout, and do some replmarks  
shenanigans for swapping out light sources.  Manual arrays with xform  
are used every once in a while, when the building supports it, but that  
is rare.  I think a lot of us rely on CAD for accuracy, I wouldn't  
worry about that; people like Greg Ward and Carsten Bauer who use vi to  
build entire Radiance scenes are in the minority, and are completely  
insane.  =8-)  Seriously, there's nothing wrong with relying on CAD for  
things; CAD is really good for things like building precision models.   
But I'd love to hear yours and others' methods for making the jump from  
CAD to Rad.

Rob Guglielmetti
rpg@rumblestrip.org
www.rumblestrip.org