What’s the point?

3D Printers, Laser Scanners, photogrammetry. Some of the words being thrown around more and more often in the ever accelerating field of rapid geometry creation, both in digital and physical forms. When you get past all the glossy brochures and marketing guff, real-world results from 3D scanning often leave a lot to be desired and don’t prove to live up to the promises often made by the various vendors providing these services. I believe that more often than not, this is because a solution may have not been well enough thought out, or too much demanded of the technology. One of the most debated areas of 3D scanning and post-processing of the captured data at the moment, is automated object recognition and solids creation from a scanned point cloud. I’m yet to see a demo of this technology that would be really useful in a real-world industry application. What I have seen so far have been “bits and pieces” of concepts that might work when fully mature.

With this in mind, I thought I’d reduce my demands in terms of what I was asking of the scanned geometry, and come up with a workflow that may be useful using some of the new tools in Autodesk Inventor 2013. The following steps outline the process I followed:

Scenario: I have a radio-controlled model aircraft that contains a GPS guided autopilot (Ardupilot.) I plan to add a GoPro camera to allow me to record my flights from the air. The only logical place to mount the camera is where the canopy used to be. To build a mount that neatly fits the canopy opening, I could trace and cut the parts by hand, but with access to a laser scanner (thanks to a demo by http://www.qubic.com.au) and the Autodesk Product Design suite of products, I thought I’d try and be a bit more “high tech” about it.

Here is the plane:

Manual Control

With Canopy Removed

The first challenge was getting the laser scan data into a point cloud format that was readable by Inventor. Inventor 2013 has tools for importing pointclouds but they currently have to be in .pcg format. The data I had from the scanner was either .obj or .asc. Having never heard of .asc, I thought I’d give Autodesk 3DS Max a go as I knew it could handle the obj format and it was in my Product Design Suite already. It imported the .obj fine and this is the result:

This is where I got stuck. I now had a polyfaced mesh but I really wanted the point cloud in Inventor and realised my mistake. Luckily, I found a product called Kubit Pointcloud which has a free edition with limited functionality that runs inside AutoCAD. With this I could import the .asc file (which I found out is just an ASCII file) which also converted it to the Autodesk .pcg format. Here is the point cloud being imported and converted inside AutoCAD:

Kubit Pointcloud Plugin for AutoCAD

Now I had my .pcg for Inventor 2013!

Using box crop tool to retain useful points in Inventor 2013

From here, I converted some of the pointcloud points to Inventor workpoints and then created a couple of workplanes on the geometry that I wanted to use as a guide.

On one of these workplanes, I created a 2D sketch and traced the shape of the canopy using a spline. I found the new “self-symmetric” spline mirror tool very useful here as I just needed to trace half of the finished shape and it made the other side continuous automatically.

Finally, a simple extrusion, and I had the first component in my camera mount ready to continue design.
I found this to be a very useful workflow once I figured out the file conversion steps. For complex shapes this could save a huge amount of time and allow you to design “in-situ.” It would be great to hear your feedback on potential applications for this.

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