My Revit experience

I previously dealt with some issues regarding the use of Digital Project. These problems arrose mostly because CATIA is not suitable for the AEC industry. Even if Digital Project is adapted to the building construction techniques, the main core, CATIA, is still a product aimed at industrial products.

Furthermore, Digital Project needs large resources both in time and money for designing anything. It can be perfectly acceptable for mass-produced objects or very complex building, but when it comes to more average construction projects, we have to find another solution.

I was wondering if I would be able to create all the precast pieces of a stone-like facade on Revit, and see what differences we can find.

Here is a little demonstration of concept for designing intricate geometry and casting drawing in Revit

Designing a specific part with the basic tool from the Revit family (extrusion and boolean operations) is not very difficult, and I quickly got the design of one of the arc over the door.

Anyway, some limitations already appears. Due to the void form created as boolean, it is impossible to merge the arc with the superior part, and a join remains.

Furthermore, there is at least one piece I was not able to draw properly a double-curved arch.

I insert my Revit family in a new project, and add a few dimensions and a section line.

A main problem appears when I am trying to extract a section of the curved part. If I get the section, I cannot add dimensions to it.

Finally, there is no embedded tool for extracting the position of the center of gravity. This information can probably be extracted using another software or the API, but we are seeking for a process developed entirely with Revit.

All these limitations made me think that Revit is not powerful enough to efficiently design intricate elements. Even if possibilities for creating complex 3D models are enough for most of the precast elements, there are still too many limitations for using it in production. I am waiting for the next releases of Revit to overcome these issues.

Parts Management in Digital Project

Because of its industrial origins, Digital Project give all its power in pieces-oriented construction project where the building can be divided in a bunch of small parts easily manageable one by one. One of my current project is the design of a set of precast concrete pieces for a stone-covered looking facade.

We have something like 2000 unique pieces of glass fiber reinforced concrete to organize, model and design. We use Digital Project for modeling these pieces, insert them in a global model for coordination purpose and extract their production drawings.

Following the production of these pieces, from the basic design to the creation of shop drawings, requires a little more investment than the usual Excel data-sheet and highlights the need for new production follow-up tools.

First, all pieces references are stored in a SQL database linked to various Excel data-sheets for visualization purpose.

These pieces are organized in a global .CATProduct, used for coordination and visualization. The main .CATProduct  datatree is regularly parsed with an .NET routine in order to check its coherence with the production records.

All .CATPart and .CATProduct are stored on a Subversion server where we can retrieve the whole editing history for each piece and cross-check it with our production records.
While reading the CATIA tree, I came through a lot of errors, mostly solved by cleaning the incriminated CATPart. After some research, it appears than the CATDUA function for checking and cleaning CATPart cannot be accessed through the CATIA API. Instead, I used the CATDUA V5 Batch utility with an hand-made configuration xml file in order to have only specific CATPart cleaned.

All data retrieved from our production records, the CATIA data tree and the SVN log are sorted and summarized to create a sound overview of our production.

These tools used here made us realise the need for a global and standardized way to follow the progress of BIM deliverable. Autodesk’s purchase of Glue and Vela System to create a global cloud-based solution along with the creation of GTeam by Gehry Technology seems to be the beginning of this new trend of product.

Parametric modeling in Revit

There is a trendy topic on the Grasshopper forum these days about links between Grasshopper and Revit, and this refers to a more general subject : How to generate parametric geometry in Revit.

Since embedded tools in Revit are mostly oriented toward classical design, workarounds have been developed to create a more complex geometry.

The Revit plug-in Dynamo, developed by Ian Keough, is one of these tools. Starting as an open source side project, it has been integrated into the Autodesk lab to became one of its most popular projects.

This tool is a graphical user interface (GUI) for parametring design directly into Revit. It looks pretty much like Grasshopper, with a canevas where we drag components link together to directly create native Revit elements.

WhiteFeet is also a Revit Plugin, which allow creating native Revit elements from an Excel datasheet. It can be used alone, but I rather use it with Hummingbird, a Grasshopper extension used to generate these Excel datasheets. There is a Grasshopper component for each major Revit command.

Designing these element in Grasshopper follow pretty much the same logic than in Revit, with family name and type, points and parameters, except of course for the possibilities offered by natives Grasshopper components.

Here is a little example for generating beams on a double-curved surface from LunchBox.

Make sure you have the correct Excel 2010 worksheet opened; I struggled for a while before realizing that my Excel version was outdated.

The Hummingbird component writes a few lines in our Excel file, something like that:

Then we go the Add-Ins panel of Revit and start the WhiteFeet Model Builder to import our datasheet. There are a few options to set, with everything quite self-explanatory.

The plugin generated smoothly these beams in Revit, with all the requested parameters:

Among Grasshopper plugins, Chameleon allows to create Revit adaptative components directly from Grasshopper. It also includes components to edit Revit parameters directly on the model.

All these plugins, among others, became a very interesting alternative to the average modeling in Revit, and fill the gap between parametric modeling and a more average BIM modelisation.

Using Digital Project

As Franck Gehry was designing is extraordinary museum in Bilbao, he had to use the only 3D modeling software available at this time, CATIA (Computer Aided Three-dimensional Interactive Application). This software, develop by the French company Dassault to help them design their aircrafts, is still nowadays the leading product for designing cars, aircrafts, or any other product with some mechanical parts.

Since CATIA is not made to design building, Franck Gehry had to use his own plugins, and created Gehry Technology to develop them. Integrated into CATIA, these plugins became the BIM software known as Digital Project.

Just to make things clear, Digital Project is the most powerful BIM software. When you start using it, you understand why the design of some of the most iconic buildings of our times involved Digital Project.

It is able to deal with very complex shapes, really large and complex models, and came with all the utilities embedded into CATIA, from PowerCopies to optimization algorithms. Buildings models can be exported in IFC, and it provides a complete set of tool to design basic architectural elements. It is not limited to buildings, but works also great with infrastructures like this footbridge:

Automation can be easily done with .Net code, and open limitless possibilities for designing complex shapes and repetitive patterns.

But it also has its drawbacks. Compared to Revit, or other traditional building modeling software like Alplan or Archicad, it’s expensive, not user friendly for a second, and frankly, not very pretty.

Dassault System had recently bought the development part of Digital Project, and I expect a new release of Digital Project based on CATIA V6 soon enough.