From Rhino to Revit

My previous post was describing how I use Grasshopper to modify a complex ceiling surface in Rhino. Once this surface is correctly modeled by taking into account constrains set by the actual construction of the ceiling (space taken by structural framing, planarity, maximal angle …), I have to create construction documentation from it.

I need to produce drawings from the 3D models of the ceiling to make it understandable by someone who will built it.

Revit will be our software of choice here. The power of Revit resides in its ability to efficiently produce drawings from a model. To be able to represent our Rhino surface on 2D drawings, we first have to create a Revit model from the Rhino surface.

After some trials and errors with the DWG export options of Rhino, I ended up exporting my surfaces as an ACIS (.sat) file, with the default Autocad export configuration.


I import this .sat file in a new Conceptual Mass family in Revit. The positioning is set to Origin to Origin to place our ceiling in its correct position regarding the origin of the massing family.


I insert this family in my Revit project, and use two dimensions to place it at the origin of the project.


This massing family allow us to create a curtain system by face, by selecting every face of our mass. I use it to create two curtain system, each one with a specific purpose.


The first one is populated only with curtain panel to represent the finish face of our ceiling. Since every panel fit a face of our massing family, we don’t need to add any subdivision into this grid. Curtain panels are 100 mm thick, and have a 50 mm offset to place their finish face along the surface of the curtain system.

I create another curtain system to model the structural element of our ceiling. This curtain system is populated with specifically designed mullion, and without any curtain panel. These mullions represent the supporting elements of our ceiling, and are modeled along the border line of each panel.


Creating a specific curtain system to model mullions allows a greater control over the elements, and does not interfere with the previously created curtain panels.

Once these panels and structure are modeled, Revit will gladly create any needed section view, with all required graphic styles and tags.


Every element is also fully documented, and therefore schedulable, allowing us to extract information like the surface of every panel, or the length of the structural framing.

I will enjoying my summer break for the next few weeks, and will put BIM 42 on hold. Next post in September!

Coordination with Grasshopper

I recently coordinate a complex ceiling with the concrete structure and mechanical equipment. This ceiling is composed of flat panels, with no particular pattern or general repetitive shape. These panels are modeled as a set of surfaces in Rhinoceros 3D.

General View

For those who are not familiar with it, Rhinoceros is a 3D modeling software solution, develop by Mc Neel Associate, and broadly used by architects in the early stage of the design. It comes in handy for design complex free-form shapes.

My ceiling surfaces have to be modified to include enough space in the plenum for mechanical equipment, while keeping the ceiling constructible.

I use different models as a reference during my work, coming mostly from Revit. Once exported in DWG, inserting them in Rhino is quite easy. These models show structural concrete and ducts to be integrated in the plenum space.

The next step is to integrate fabrication constrains, in order to keep every ceiling panels constructible while editing them. To do so, I use Grasshopper, the visual programming interface of Rhinoceros.

With a layer pipeline, I extract every panel of the ceiling surface. I then apply the construction rules on these panels, and display the result with a specific presentation in Rhino.

For example, since every panel must be planar, I display every non-flat panel in red, and correct them as soon I see them in Rhino.



I also display the naked edge curves of every panel to identify junction problems between two supposedly contiguous panels.



Each ceiling panel needs also some space behind it for its supporting structure. The volume of this structure is modeled in real time using the offset command in Grasshopper. Another constrain is the angle of the panel vertices. After fighting with some angle measure in Grasshopper, I ending up by just counting the number of edge of a panel, displaying it as a color scheme in Rhino, and assuming that the smallest edges count was the better.



Once these construction constrains are displayed in real time in the Rhino viewport, I can easily modified the ceiling surface while making sure it still constructible. These modifications are conducted here with basic surface modeling tools, and entirely by hand. But once you have immediate feedback on what you are doing thanks to Grasshopper, editing these surfaces become almost fun.

Geometry Gym

I was talking on a previous article about the Grasshopper plugin develop by Jon Mirtschin called Geometry Gym.

This set of tool for building modeling firstly came as a plugin for Rhino, implementing commands for designing structures and linking these models to structural analysis software.

These tools where integrated as commands in Grasshopper, allowing generating building elements parametrically, a very interesting feature at an early stage of the project.

But for me, the most interesting part of this plugin is its ability to generate IFC files into Grasshopper. A large part of the IFC classes are implemented directly as Grasshopper functions.

By combining these functions, we generate the structure of our IFC file exactly as we want it, and if our favorite BIM software is known for missing some IFC classes, we can still use a workaround by designing yourself your IFC data structure.

Using this plugin requires a little understanding of the IFC data structure, but examples can be found on the Geometry Gym blog, and are quite self-explaining.

Combined with the building modeling tools described above, it provides a powerful way of designing building, especially at the early stage of the project.

Geometry Gym came also with various plugins used as bridges for other BIM software

The plugin for Revit implement a new IFC Import module, especially design to import files generated in Grasshopper. This allows integrating native Revit element from an IFC file.

There is also a direct link with Tekla, use to generate native Tekla elements directly from the Grasshopper model.

If this software need some time to get used to it, and a little knowledge about the IFC Data structure, once taken in hand, it become powerful enough for replace any conventional BIM software, at least at the beginning of a project, and especially for complex shapes and structures.

About Grasshopper

Did you ever try using Rhino? I know, I know, it’s not a BIM software, it’s just able to make pretty 3D drawings and nice pictures. But, as I have already said, nice pictures are still the best way to sell the BIM, and Rhino is actually a great software.

Apart from its capacities to design every shape you can imagine and its user friendly interface, Rhino come with a lot of plugin which make it really powerful.

Among these plugins, my favorite is Grasshopper. It’s a graphical interface for designing parametric shapes in Rhino. In other word, instead of simply drawing what you imagine, you explain to Grasshopper what you’re imagining, and it designs it for you.

As an illustration, here is the interface of Grasshopper, alongside with Rhino. Pretty, isn’t it? The red surface in Rhino is the visualization of what we are designing in Grasshopper by wiring these little boxes together.

As an example, we can start by generating twenty points randomly:

Then we use them to draw twenty circles:

And finally, we extrude each circle to create cylinders:

And the best part is that we can still edit anything you want.

If you want fewer cylinders, just change the number of origin points:

Or change the circle’s radius:

The possibilities are almost endless, and, shame on me, I start to think that this little plugin can even be more powerful than the almighty CATIA. At least, it’s far less expensive, since it came freely with a license for Rhino.

You can find a lot of help on the Grasshopper forum, and a beginners Guide here. I’m also very fond of the Grasshopper Learning Material made by Woo Jae Sung

Grasshopper has its own plugins and developing interface, which make it even more useful. I will probably talk again about these plugins, some of them has become a full part of our BIM workflow.