Opening Mesh File Formats in Alibre Design

A prospective customer put this question to me today:

It has been great trying to use SYCODE software to import 3DS files from ArchiCAD to Alibre. I would love to work with both platforms more interconnected. Do you have a suggestion of how I could do that? I plan to use Alibre Design for my structural working shop floor steel fabrication details for units designed with ArchiCAD. I know Telka is great for this, but so is its price. More information will be greatly appreciated.

While we do not have an ArchiCAD to Alibre Design bridge, there is something else I would like to mention about opening mesh formats like 3DS into Alibre Design. We often receive support requests on this issue. So I decided to write my thoughts here on this blog for the benefit of others trying to do the same thing.

Here is the thing. Alibre Design is a solid modeling system. It does not have a mesh data structure. Neither does it have a mesh visualization structure like SolidWorks or Pro/ENGINEER. That’s why our Alibre Design add-ons that import mesh formats like 3D Studio (3DS), Wavefront (OBJ), SketchUp (SKP), Stereolithography (STL) and Visualization Toolkit (VTK) need to cough up solid models from the mesh objects described in these mesh files. So this task is not a simple conversion from one data structure in one format to another data structure in another format, which is what happens say in the case of importing a STEP file into Alibre Design. The task involves creating a trimmed planar NURBS surface for each triangle/quad of the mesh and then stitching them together to yield a closed solid or an open surface.

Maybe I should explain this by means of an example. Assume that we have a simple solid model of a sphere stored in a STEP file. The solid model contains just one closed spherical surface. Alibre Design’s STEP file importer simply reads the spherical surface stored in the STEP file and converts into a spherical surface in Alibre Design. However, the same sphere in a 3DS file would be stored as a mesh object consisting of maybe 200 triangular faces depending on the resolution selected when saving the 3DS file. So our 3DS importer add-on for Alibre Design needs to create 200 planar surfaces, trim them and stitch them together into a solid. This takes a lot of computing resources as well as time.

In fact, the time required increases exponentially with the number of faces to create, trim and stitch. So if you have a huge mesh containing thousands of faces, you are going to end up staring at a progress bar that appears to be stuck up. In reality the add-on is working overtime. The Task Manager will verify that.

So my advice to anyone trying to open a mesh format into Alibre Design (or for that matter, any other solid modeling system) is to try and break down the mesh into parts if possible. Unfortunately, in the case of STL, that cannot be done since a STL file holds all triangles as a single mesh object. But the other mesh formats I mentioned above can all store more than one mesh objects.

So in the case of the prospective customer I mentioned above, it would make sense to save individual objects or small groups of them in ArchiCAD to individual 3DS files and then import them one by one into Alibre Design using our add-on. I understand that the process may seem a bit tedious, especially for large models. But this method may actually end up yielding a desirable outcome as opposed to waiting endlessly for the add-on to stitch thousands of triangles and possibly run out of memory.

If you have any questions related to this issue, please do leave a comment. I will try my best to get you an answer or suggest a workaround.