RE: Revit

From: Charles Overy (
Date: Tue Apr 22 2003 - 20:06:16 EEST


I think that the generation of watertight output, ie "valid stl" should not
be a primary criteria for Architectural CAD selection. The adoption of BIM
and parametrics as well as the integration of tool sets that more accurately
model the actual architectural design flow are far more important.

My view is that CAD and related computer technologies are predominately
used in the architectural fields as a method of documentation not as tools
to facilitate creativity and collaboration. (Part of my concern over
Laiserin's drive to BIM is that it appears to me to prioritize
documentation as a method of increasing the value of CAD in AEC).

What I believe was significant in the adoption of computer technologies in
other industries is that the automation of some of the design tasks
definitively improved the aesthetic and functional quality of the designs.
The frequent feedback I get from my customers it that this is far from a
universally accepted truth in architecture.

Clearly I am biased by my own efforts but I believe rapid modeling will be
useful to the AEC profession. However, it will not be successful if it
requires significant user intervention for the generation of "watertight"
stl files as we, in this forum, currently understand that requirement.
(Happy to expound upon why that is not possible if you would like!)

OK, to cut a dissertation short, watch Revit for what it is, AutoDesk's next
generation parametric AEC modeler. As I understand BIM, Revit is it. I do
not see any other real competition in this class although as I mention I am
not very familiar with Bentley systems. Whether Revit will morph into
AutoCAD AEC or the other way around is probably a function of AutoDesk's
internal workings. Again, BIM-centric programs, and most of the big AEC
modelers, to me, add very little, if anything to the creative process for
the majority of current architects. For this lightweight, but inherently 3D
programs like Sketch up seem to have an edge.

As for RP, I see two scenarios. One, the RP industry has to be
significantly compelling for AEC CAD vendors to incorporate viable RP output
into their software. To truly create good RP output from a wide variety of
AEC models this would require parametric substitution based on output model
scale when the export file is generated. This is far more complex than
generating valid STL export. The second road is the one we have taken, the
initial R&D of "middle ware" that specifically addresses the AEC issue.
Perhaps it is the road less traveled. I certainly hope it is not a dead



-----Original Message-----
From: []On
Behalf Of Makai Smith
Sent: Tuesday, April 22, 2003 5:48 AM
To:; Bob Olsen;
Subject: RE: Revit

Very interesting. To bad Revit dropped the ball. I am looking forward to
seeing your resurfacing tool. There seems to be a lesson for architects and
the allied arts in what you are doing: that we cannot wait idly and use the
tools vendors provide us. Out of necessity we must have an active role in
creating them.

>From your experience with architecturally oriented software, can you cite
any examples of those with strengths in both parametric creation and
watertight output (, for < $25k/seat?) IOW, that which might support
both BIM and RP? We are currently an AutoCAD shop. While encouraging a
move to next gen software its easy to suggest staying Autodesk, but I wonder
if there are better alternatives. Anyone?


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-----Original Message-----
From: Charles Overy []
Sent: Monday, April 21, 2003 9:12 PM
To: Bob Olsen;
Subject: RE: Revit


In a word NO.

More Detail:
Revit, only has three "built in" export formats
DWG - AutoCad
DXF - generic CAD export
DGN - Bently Systems

As of last fall it was not exporting ACIS or other solids data to Autocad,
only a tessellated mesh.
Great you might say, a tessellated mesh, I can go to STL from a tessellated
mesh via 3ds or the like.

However, meshes that I exported from Revit were HIGHLY degenerate. They
had holes, flipped faces, etc.
I would be happy to send you some if you want to have a look. I have not
worked with the DGN as I do not have Bentley. The DXF closely mirrors the
DWG. They could be used as a snap grid to redraw the geometry but were not
useful in anything more that very basic cases as a starting point for mesh

In addition, if you are considering building Architectural models from Revit
files you will face the problem that I call radical scale down. Basically,
even if you own a 810, Titan or the like you are going to be running an arch
model at say 1" = 8' or smaller. 1/96th the original size to maybe 1/400
the real world size. Now Revit is great program because it is truly
parametric. You can call up a window and place it into a wall. Revit also
knows the thickness of the glass in the window. Even expensive .25" glass at
1/96 then is .0026" thick when you make the prototype. Now imagine a small
office building with a "curtain wall" of glass representing 60 percent of
the model and the model at 1" = 20' . You just built a Vat O' Dust.
Because it is a parametric modeler, you could create window substitutions,
but depending on the window library you cannot always just say you want 1'
thick glass. Sometimes you have to modify each window.... Now what about a
steel I beam with a .25" section... or a cable holding up a fabric canopy...

Have I been there... yes.
I have had meetings with Revit's old director of sales and their current
CEO. At one point they were going to write STL export into the code for us
(we were going to guarantee sales or pay) but that was before they got
purchased by Autodesk. We ran several sample models for them which they
liked. As of last fall there was no movement that I could ascertain to
embrace RP.

In the end we resorted to development of a more general solution to at
least some of the problems that I describe above. The software solution
solves some of the radical scale down issues and can work with existing RP
mesh preprocessing software like Magics, Marcam, Stl Editor, to create a
buildable mesh. The plan is to have operational stl file resurfacing
available late next week.

Please let me know if you would like further information on Revit, RP in
architecture, or our solutions.

Best wishes

Charles Overy
Director of Engineering, LGM

-----Original Message-----
From: []On Behalf Of
Bob Olsen
Sent: Monday, April 21, 2003 4:32 PM
To: ''
Subject: Revit

Anyone know if AutoDesk's Revit software (an architectural package) can
create an STL file, or how that is done? Thanks in advance!
Regards, Bob
Protogenic - Always on time,
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Bob Olsen sales manager
1490 West 121st Avenue, Suite 101
Westminster, CO 80234-3497

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