This article provides information on the Max error value in Artec Studio 11/12, formerly called the Quality parameter in Artec Studio versions 10 and older.
What is the Max error/Quality value?
- Max error is an internal parameter that is calculated for every 3D frame in each Scan (the value is a purely internal Artec Studio metric and is neither in mm nor in percent).
- The Max error value of a Scan is equal to the Max error value of the Scan's least accurate frame.
- This value allows you to gauge whether the frames in a given Scan are aligned correctly in relation to each other and indicates how precise their alignment is.
- A higher Max error number signifies a less accurate alignment. Therefore: the lower the Max error value - the better the quality of the Scan.
Acceptable Max error ranges
As you start analyzing your scans and frames, keep in mind the following rules:
- The Max error value only becomes meaningful after running the Global Registration algorithm.
- The bigger the size of your scanned object, the higher the acceptable Max error (this is due to error accumulation over distance).
Max error ranges for the Artec Eva/Eva Lite:
- 0.0 - 0.3 = great scan quality
- 0.4 - 0.7 = great for large objects, acceptable for small and medium objects
- 0.8 - 1.2 = acceptable for large and very large objects, but unacceptable for small and medium objects
- 1.2+ = acceptable for very large objects. The bigger the object, the higher the acceptable number (for example, a Max error of 2.5 is perfectly ok for a scan of a car)
Max error ranges for the Artec Space Spider/Spider:
- 0.0 = perfect scan
- 0.1 = great quality
- 0.2 = good
- 0.3 = acceptable, but don't expect a very high resolution from your fusion
- 0.4+ = acceptable only for large objects
Max error ranges for Intel RealSense sensors:
- 0.4 - 1 = great quality
- 1 - 2 = very good quality
- 2 - 3 = good for smaller, great for larger objects
- 3 - 4 = acceptable
- 4+ = the bigger the object, the higher the acceptable number
What if my Max error is beyond the acceptable range?
As mentioned above, the Max error value only becomes meaningful after the Global Registration algorithm is run.
Begin by making sure that you have run the Global Registration algorithm with the appropriate settings (more information on recommended settings can be found here). Please also note that the Global Registration algorithm can only be performed successfully on scans that are correctly aligned in relation to each other.
The Global Registration algorithm works by "tightening" the registration (fine alignment) of all individual frames contained in the Scan(s) selected in the Workspace. Once applied, Global Registration finds the optimal position for every single frame in all of the selected Scans.
After a Global Registration operation, some frames may end up with abnormally high Max Error values or even a "Failed" status. These are frames which have insufficient geometry and/or texture features and can therefore not be correctly registered to their neighboring frames. The possible reasons for the existence of these substandard frames are listed below:
- The 3D scanner operator captured the object (entirely or in part) at an incorrect scanning distance (too close or too far) or at an excessively high speed.
- The 3D scanning path and scanner handling were not optimal, resulting in a number of frames containing insufficient features (these frames will often look like fragments, as pictured in the leg scan example further below).
- The PC which was used for the scanning session was below the recommended requirements, resulting in a low capture frame-rate and a suboptimal scanning session.
- The object was too reflective, was covered in fuzzy fur or hair, or was otherwise difficult to scan, while the necessary preparations were neglected (e.g. spraying the object with anti-reflective spray).
In the picture below you can see an example of an incorrectly captured frame of a human leg. Frame 74, which clearly is a fragment, does not have sufficient 3D geometry to be registered correctly in relation to its neighboring frames:
Frame 169, on the other hand, is captured and registered correctly:
Note: Even if your data is suboptimal and has an excessively high Max error number, it may still be possible to create a decent 3D model with the help of various powerful post-processing algorithms included in Artec Studio. However, in order to achieve the best possible results in the shortest amount of time, starting over and capturing a good scan of the object is recommended. This approach will be faster and less involved.
Setting the correct Fusion resolution in relation to the Max error value
The Autopilot mode in Artec Studio 11/12 automatically chooses the optimal Fusion type as well as the Fusion resolution value based on the Max error value and the size of the scanned object.
For manual post-processing, you may set your Fusion resolution value based on the suggestions listed below. Please consider these values as recommendations rather than hard rules.
|Artec Eva / Eva Lite||Artec Space Spider / Spider||Intel RealSense|
0.5 = minimum recommended value. Use only with high-quality scan data (Max error values below 0.3)
0.15 = minimum recommended value. Use only with high-quality scan data (Max error values 0.0 - 0.1)
1.5 = minimum recommended value. Use only with high-quality scan data (Max error values 0.4 - 1)
1 = default value, good for most cases (Max error values 0.4 - 0.7)
0.2 = use on raw scans with an 0.2 Max error value
2 - 2.5 = use on raw scans with a 1 - 2 Max error value
1.5 - 2 = good for Eva scans with acceptable Max error values (0.8 - 1.2) or for large objects
0.3 = default value, good for raw scans with an acceptable Max error value (0.3 and lower)
3 = default value, good for average quality scans with a Max error value of 2 - 3
3+ = good for very large objects, e.g. cars
0.4 - 0.5 = good for smoothing geometry and hiding minor misalignments
4+ = good for smoothing geometry and hiding minor misalignments
Note: When using the Smooth Fusion algorithm, you may select a resolution twice smaller than the recommendations above. When doing so, we still recommend avoiding values lower than the minimum recommended fusion resolution parameter.
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