A bounding box, initiated with the first captured frame, is a 3D cube that delineates the permissible area for scanned data. Any data outside this cube will not be collected. Unawareness of this limitation can lead to misinterpretations of data capture, as illustrated in the GIF. However, this feature is crucial for maintaining the precision and integrity of the scanned data.
This is a critical consideration before initiating any scan, particularly for large objects, as neglecting it could impede the successful completion of the scan.
Size of Bounding Box
The bounding box size is determined by the formula: " Size of bounding box = Point distance(mm) . 8192 ". Since 8192 is a constant, the bounding box size is directly dependent on the chosen point distance, or resolution. The table below illustrates the various bounding box sizes.
RESOLUTION | POINT DISTANCE (mm) | BOUNDING BOX SIZE (m) |
High | 0,2 | 1.638 |
High | 0,3 | 2.458 |
Medium | 0,5 | 4.096 |
Medium | 0,7 | 5.734 |
| Low | 1 | 8.192 |
Low | 1,5 | 12.288 |
Low | 3 | 24.576 |
Therefore, your
chosen resolution directly influences the size of the scannable 3D space, with
the bounding box ranging from a minimum of 1.638 meters to a maximum of 24.576
meters.
Location and orientation
The initial position and orientation of the scanner determine the location of the bounding box. The scanner's placement dictates the geometric center of the bounding box, and its orientation determines the direction of the Coordinate System (CSYS), as illustrated in the image below.
The scanner's initial position relative to the object dictates both the bounding box's location and orientation. The clip below shows the scanner's position within an 8,192-meter bounding box at the moment of its creation.
Note: No scanned data can be stored outside the confines of the orange box.
Placement of the object within the Bounding box and the Scan initiation point
As the initial scanned frame dictates the bounding box's center, careful consideration of the scan's starting point is crucial. The following clip demonstrates scanning a 4.78-meter car at 1mm resolution, resulting in an 8.192-meter bounding box.
Since the scan commenced at the front of the car, a portion of the vehicle extends beyond the bounding box, rendering it unscannable within the current project. To capture the entire object, one could either initiate a new project or restart the current scan with a greater point distance, thereby expanding the bounding box's dimensions.
Now, let's examine the outcome if the operator chooses to begin scanning from one side of the car.
For a comprehensive scan within a single project, it is essential to initiate scanning near the object's center, allowing the bounding box to encompass its entirety.
Note: Markers and bounding box
As observed in the initial clip, the bounding box exclusively impacts 3D scanned data; markers can be scanned beyond their boundaries. It is important to note that EXScan Pro v3.6.0.5 software permits an unlimited number of scanned markers, though the Global Marker File (GMF) has a capacity limit of 5,000 markers. In contrast, EXScan HX v1.2.0.4 software extends the GMF limit to 20,000 markers.
Conclusion
The bounding box defines the 3D space for scanned data. Its size is resolution-dependent, with a minimum of 8.192 meters. The box's position is determined by the scanner's initial location and orientation, making strategic scan initiation, especially for large objects, crucial. Bounding box size is irrelevant for markers, which can be captured outside its limits.