With the popularization of laser scanning in industrial applications ranging from inspection to reverse engineering, it is important to understand how to properly clean a point cloud of noise, outliers and irrelevant points before any analysis or meshing can be performed. Today we’ll take a look at a proper cloud-cleaning procedure done using BuildIT.
Why clean your point cloud?
The main objective of Point Cloud Cleaning is to get rid of the irrelevant points that were recorded during the digitalization of the part. Scans are often clouded with measurement noise due to reflection off of surfaces or points captured from the support structure of the inspected part. And so, in order to keep only those points valuable to the inspection or to create a proper mesh, getting rid of the outlier points is important.
Below you’ll see a scan cloud of a hand on a desk. For this example, we only want to retain the cleaned scan cloud of the hand. We will want to separate out the supporting desk from the hand’s scan cloud, and then clean up any outliers.
First, using the Extract Surface from Cloud command we’ll create the bottom plane, which was the table we measured our object on. We’ll start by selecting the merged Cloud, with ‘Plane’ as the Surface Type, and then select 3 points from the cloud. We’ll also adjust the Tolerance to the scanner’s tolerance. This will include the points within that tolerance in the best fitting of this plane. This command will automatically split the Cloud allowing it to be cleaned up easily and efficiently. We can hide the newly created cloud to considerably reduce the number of undesirable points for our inspection.
Next, we’ll use the clipping plane option to get rid of all outliers on the desk surface. By selecting the extracted plane and the preview tool, we can easily apply the appropriate Offset for the task. Here we wanted to keep only the points on the top of the hand.
Last, we’ll use Edit>Point Cloud >Split Clouds Polygon selection tool to get rid of rogue points in the cloud. We simply select the cloud, toggle Polygon selection and click the selection button. We can then lasso the points which we wish to remove from the cloud, and hit apply.
Now that our cloud is cleaned, switching the Point Style to Shaded Disc will help to visualize the scanned object. We are now ready perform an inspection or proceed in creating a mesh for reverse engineering.