Convert Revit Models to Solid Models for Rapid Prototyping

[Andre Baros]

Does anyone have any experience with, or any suggested on, converting a Revit model to a solid model for Rapid Prototyping. I suppose it would be a process involving the DWG intermediary file, but I'm not sure what the best next step is. We've done a bit of Rapid Prototyping from Acad with great results and it seams like it would make sense to take advantage of our shiny new Revit Models.

[GuyR]

Converting to STL is the straight forward bit. There are a number of converters converters out there that can handle it.

The big issue is the resolution of your intended Rapid prototyping method. Scale a mullion down to the scale of the STL model you've producing and compare this to the resolution of the machine. You'll probably find it's tight.

Guy

[hand471037]

I'm working on this very thing right now. When you bring a Revit model into AutoCAD, everything becomes a polyface mesh. So if your rapid prototyping software only reads solids, you're gonna have some trouble. If you have Viz/Max, with the new plug-in, you could open your Revit models there and then feed them to the prototyper, for there are many add-ons I've seen for Max for that very purpose, also Viz/Max (I believe) can export VRML, STL, IGES, which many of these systems use.

The other option you could have is to export your Revit model to a DXF, and then import it into whatever program generates the g-code and go from there. Are you doing the prototyping yourself, or is someone else doing it from your files?

[Andre Baros]

Regarding small details, we use the rapid prototype to build the mas, have the small parts laser cut, and then assemble the two by hand... they ship better this way as well.

So far, we've been sending files out to be built on a Z-Corp machine. What I'm looking for is specific software for converting the surfaces to solids reliably. The range of programs out there is HUGE and I was hoping to narrow my search a little. I didn't realize I could produce solids from MAX... I'll have to look into that.

Andre

One more thing... what "new plug-in for Viz/Max"???

[cwho]

Andre,

Good to see your post here!

It certainly is possible to create Rapid Prototype models from Revit data. In fact, because Revit is inherently a 3D modeler I believe that Rapid Prototyping can become an innovative and cost effective way to see and present your Revit models.

There are actually two approaches that we use to create prototypable files from AEC data. First we use a software program that we developed in house to convert complex geometry for rapid prototyping . In the last month we have put a version online at www.CADSpan.com (http://www.cadspan.com/).

This software is specifically designed to take AEC data, either 3ds, DXF, lwo, vrml, stl, obj. and create a buildable stl file. It essentially "shrink wraps" the geometry of the building to create a buildable stl file. This utility is very useful if you have a complex model, or a conceptual model and need to 3D print a massing model. The algorithms eliminate all of the interior details creating a representation of the building envelope. We are currently beta testing the online version with Revit's DXF export as a way to create 3D models directly from Revit.

CADSpan essentially solves the very valid issues that Guy brings up in his post. However, CADSpan resurfaces the geometry at the resolution of the 3D printer. (it was designed for the Z Corporation printers) If you have super fine mullions on a skyscraper, they will not resolve on the resurfacing because they will not show up on the RP model. If you have the same mullions on a garden shed, they will resolve.

The alternate route is more complex but can work if you need to preserve more detail than is possible with the CADSpan engine. It is really the brute force approach. For this, I am not as familiar with it using Revit files as we are with ACAD or other output. Essentially you try to preserve the CAD solids data and export to a polygon mesh format as late in the translation process as possible. For Revit, I believe, you have added a step because you cannot preserve solids as you move from Revit to AutoCAD. Please correct me if I am wrong on this. Anyway, you eventually go to a 3DS file and use a variety of file translation softwares (we use 3D Compress) to move from one mesh format to another. Once you have an stl you need to edit it using a program like Materialise Magics to fix any geometry that the RP machines would be unhappy with. As Magics runs about $6000, this is not an easy path. It is possible to do without Magics or with other stl prep programs. Basically the convoluted nature as well as the difficulty of this path is why we developed CADSpan. However, this method can work well in specific cases. (Like your ACAD building where you had drawn making good use of solids). It really depends on the designer understanding how to ONLY use solids in their design. This can be pretty limiting.

We are currently developing our new service RapidArchitect.com to offer assistance and rapid RP modelmaking for Revit Customers. Using this service you will be able to upload a Revit file or Revit DXF export and have a model quoted and built within a few days.

< SNIP EDIT >

Also, our team would very much like to have some Revit files from the general user community in order to prove out our algorithms, write manuals, and use as samples. If you would like a FREE RP model, (no bigger than 10" x 8" x 6" ) please send me a Revit file. In turn we need full "right to use" the model in marketing, web, trade shows and the like. We are happy to credit you or your firm with the design. A good candidate for this would be a building with a well defined building envelope and not too many fine exterior details. The Revit model needs to be at a stage where the building is "dried in ", in other words it needs to have windows and doors and have all the walls in etc. If we cannot use the file I will certainly give you feedback as to why it is difficult or not possible to RP the geometry.

< SNIP EDIT >

Best wishes

Charles Overy
Director, LGM

Edited to comply with AUGI guidelines

[Andre Baros]

So next time, I can just send you a Revit file and we see what happens?

PS. We finished a very nice model with LGM earlier this year and are working on a second at the moment. These models have been slightly more complex than average and LGM has really helped out in getting them realized. Both were of a legacy project still done in AutoCAD.

[cwho]

Yes. Or better yet, send us a sample now! Then when the next time comes along we will all know the process is robust. Stay tuned and we will report progress...

[cwentworth]

To get a model from Revit is easy. Just out put the file to DWG polymesh and bring it into 3D studio and save as a VRML file for color or STL file for monochrome. We do it as a service. If you like we can do it for you. Attached are some samples.

Thanks,
Chris
www.3drp.com