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.

Digital Project Automation

Aside from a lot of features, CATIA, and so Digital Project, comes with powerful automation tools.

Knowledge Templates is a programming language interface, tightly integrated into CATIA, allowing adding rules on a design. You can link various geometrical parameters to a single one which will update the whole geometry regarding its value.  For example, we used this functionality to create a rule which change the section of steel beams regarding their position in the whole structure. These rules are part of the CATIA tree and are automatically updated with design changes. You can also use them for calling more complex automation code written in CATVBA.

CATVBA is the programming language of CATIA. Based on VBA, it came with a developing interface looking more or less like the Excel one, and made any development pretty easy. Most of the functions of CATIA and Digital Project have their equivalent in CATVBA, and you can use these tools for any repetitive tasks. We used it to generate the covering panels of a large double curved roof. One panel was design carefully, using four points for its positioning, then duplicate automatically all over the roof, each panel adapting itself on its positioning points.

But as we were running this routine, we struggle with memory load problems, leading our application to crash after too much instantiations. We finally decide to use a .NET application running outside Digital Project to drive it. Most function of CATVBA can be used in .NET, so we rewrite our panels instantiation routine on Visual Studio (the Express version), adding some code to close and restart Digital Project when the memory load became too important. We finally manage to populate properly the whole roof surface with our panels, after running the application for nearly 48 hours (It was a really large roof…).

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.