For most people, acquiring 3D scan data is fast and easy once the 3D scanner is set up and the settings are adjusted accordingly. The process then becomes pretty automated. Press the scan button, wait a few seconds, and you have millions of measurements to work with.
Depending on the complexity of the object, 3D scanning a complete object generally takes 15 minutes and approximately 15 to 30 scans. The next step is to align and process the 3D scanner data into a single 3D mesh. The time it takes for this process can vary from 15 minutes to an hour.
I like to share some of my own tips and tricks for processing 3D scan data fast while retaining the accuracy.
1) Lower the scan density and decimate your data
Generally there is no need to keep your raw scans at 100% density. Decimating to 50% or 75% of your mesh data rarely changes the final result. Decimation algorithms will keep the data where it is important and throw away useless data.
Since many of the processing algorithms can take exponentially more time, removing unneeded data early on will give you immense time savings.
2) Delete overlapping data
After the 3D meshes have been aligned, it is common for a single section of an object to have been scanned 4-6 times because of overlapping 3D scans. This data will make merging the data more difficult and causes the results to be less accurate. Keep the data from the 3D scan that has the best view of the area and delete the rest. By doing this you can easy drop the number of mesh points by 40%. Remember to align first before deleting the extra data.
3) Operate on the point cloud instead of the mesh
Point clouds render faster and can process faster than meshes. Perform all your operations on points and do a final merge to mesh at the end. The exact steps differ depending on if you are using FlexScan3D, Leios, Geomagic or other 3D scanner data process software but for very big meshes, working as points has been a time saver.
4) Ensure quality incoming data
As the saying goes, “Garbage in, Garbage out”. In processing 3D scanner data, getting clean and easily aligned 3D scanner data from the get-go would be ideal. Capturing messy data from the 3D scanner and having to deal with noise cleanup is the difference between needing to spend 10 minutes on your data and having to spend 10 days on the cleanup project.
5) Capture overlapping scan segments
There’s nothing more frustrating than being almost 80% complete on the scan cleanup and having the last few scans not aligning properly. It is impossible to correctly align two flat planes. Make sure you have 30% overlap with another 3D scan, and that the 30% over includes enough unique geometry.
For particular tricky scans, if you have FlexScan3D you can make use the software’s photogrammetry data alignment feature to solve more complicated alignment issues.
6) Use a volumetric merge
Most 3D scanner data processing packages offer two types of merge algorithms. 1) A “strict” merge where each point is used and connected 2) A looser volumetric merge that is not as accurate but is more tolerant of noise and automatically fills in holes. Unless you need every last micron of accuracy, using a volumetric merge will save you a lot of time.
FlexScan3D uses a volumetric merge, so after processing in an external tool like Leios or Geomagic, you can always import your meshes back in to FlexScan3D for a volumetric merge.
7) Upgrade your PC
Computer equipment is getting more inexpensive so there is no point wasting hours waiting for scan alignment and merging when spending a couple hundred dollars will pay for itself with in a single scan job. Having a 64-bit workstation system with lots of ram and an SSD hardware makes a huge difference. Don’t forget the fancy graphics card! :-)
Over the years our team had to scan and deliver complex scan data in very tight timelines. These tricks have saved us time and time again. I hope some of these tips and tricks will help you save some time in your next scanning project.
This blog post was previously posted on Tue, Aug 2, 2011 on 3D3 Solutions blog. LMI Technologies acquired 3D3 Solutions on May 1, 2013.
Posted by Thomas Tong