Today, I will be using a plastic snow shovel to demonstrate how to overcome the challenge of 3D scanning objects with thin walls. Normally, we would scan an object one side at a time while laying flat on the ground then use the Automatic Base Removal tool to take away the floor and automatically match the scans in the software. In this video, I will demonstrate a technique that we can use to help scan thin-walled objects with an Artec scanner and post-process the scan data with Artec Studio.
Scanning Thin-walled Objects
The challenge with a thin-walled object is that there is very little overlap between the scans and the scanner has a hard time registering these points. In order to overcome this challenge, we will take a few additional views of the object and use the environment to our advantage. I’m going to use the wood grain pattern on the floor to do four scans and each time we scan, we’re going to keep the floor as part of our data set. Normally when we are scanning an object, we use the Automatic Base Removal tool and it would remove the floor. That feature has a lot of advantages, but here, we want to keep the floor in the scan for this situation.
The problem with this thin-walled object is the scanner tracks by comparing every frame to the frames around it. And on a thin-walled object, like this shovel, that’s going to work great when we’re flat to the surface, but we’re going to have moments where passing across the front to back transition only yields a small sliver of data as we’re looking directly at the edge of the shovel. By scanning and including other objects, in this case, the wood grain floor in the data set, we give the software something else to “read” when we get to the point of global registration. The consequence is we need to change the order of the normal steps in the process.
Steps to overcoming the challenge
Typically before we combine these scans in Artec Studio, we would subtract the base, but we want to leave them in their past global registration. As a result of taking these steps in this order, we’re going to have an awkward moment in the software where we see all four scans together before we’ve deleted the wood grain floor. It is going to look like it’s sandwiched between four different planes of wood. That is okay. I like to use a micro SD card to transfer this data into Artec Studio.
Below we see our four different scans in four different positions. I like using the wood grain floor in this room, especially because Artec software will use not just geometry features, but also “see” the color markings to help orient all of the scan frames into the correct relative location to each other using global registration. And there’s really nothing that works better than a wood grain pattern. The irregular color pattern is perfect for the Artec scanners. If we didn’t have a wood grain floor with markings to help global registration orient, we could scan on top of a piece of newspaper that has text printed on it.
Now looking at this in an x-ray mode, we’ll see that we’ve got all of our scans aligned and it’s sandwiched between these four different patches of floor. We are running global registration, which realigns all the frames of the scan to match up as perfectly as possible. In the next step, we will go through the scan with the editor tools and erase what we don’t want.
The last step in the process is sharp fusion. The end result is going to be that we get a single object with both the front and back side of this thin wall surface all aligned to each other correctly.
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