[Radiance-general] Modeling Paradox

[Jeffrey McGrew]

> Hi Jeffrey,
> 
> What CAD program are you using?  What exporter are you using?

I am using AutoDesk Revit for the modeling, then exporting
from that to AutoCAD where everything becomes a polyface mesh,
and then using RADOUT to generate my .RAD files. The other
approach I've done is to export from Revit to DXF in parts,
and then use the DXF2RAD tool to translate them into .RAD.

The problem I have, and hence why I have to use AutoCAD
as an intermediary currently, is that AutoDesk Revit doesn't
have the ability to export geometry so that material = layer
within a DXF or DWG; instead it places elements upon layers
based upon those elements classification; i.e. existing walls,
new furniture, site elements, etc. Revit also currently lacks
an API, so I can't write my own Radiance exporter for it.

So, the best way I've found to export from Revit to
Radiance is to first export to a DWG or DXF file, open
that in AutoCAD, swap things onto layers per what
material I want them to be, then use RADOUT to generate
multiple .RAD files.

However the modeling capabilities of Revit *far* outshine
those of AutoCAD when it comes to modeling buildings; so
even having to jump through these translation hoops, it's
still faster than modeling in AutoCAD to begin with. Revit
is, more or less, 'Inventor or SolidEdge for Architects'.

>  You have  
> to understand that the basic building block of ACIS-based modeling  
> programs -- when talking to other software -- is the damned 
> triangle,  
> unfortunately.

That's what I've encountered.
  
> It's not a  
> Radiance limitation, it's an ACIS translation problem.

Oh no, I never ment to imply that it was a Radiance
limitation; I meant to imply that it was a limitation
with the translation programs; in that
they aren't aware enough to translate, say, a cylinder
in a DXF to a cylinder in Radiance.

> 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.  

Another benefit of using AutoCAD as an intermediary
from Revit is what you mention here; indeed using the
RADOUT tool I've had much less issue with aiming failures,
as well as replacing the luminescent parts of my light
fixtures within AutoCAD with simple AutoCAD 3Dface elements
has helped immensely.

> 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).

I'm not using Soilds anymore; when I export from
Revit, everything comes into AutoCAD as a polyface
mesh.

> 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/200
> 3-August/ 
> 000946.html]!)

Thanks a great deal for this link. I'm certain that
this will help a great deal! Something like this
was exactly what I was looking for; lacking the
ability to make 'good' RAD files directly from
my CAD software, I needed some way to easily
'swap' elements within my scenes. Thanks again!
 
> 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.

This sounds like what I'll do, at least until
Revit has an API!

Thanks again,

Jeffrey