by WalterMo » Sun Jul 22, 2012 8:58 am
There are different ways to align a series of scans which were scanned on a turntable. The following example with an antique Opel should show how I mainly do it.
The most important requirement is that the axis of the turntable is the very same as the coordinate system used by DAVID. But also 'Alignment around' x and z can be used if you orientate the turntable axis horizontally parallel to the corner walls. See the sketch.
The car was mounted on the vertical (Y) axis and was scanned at 8 positions à 45°. The direction of rotation was counter-clockwise (top view). If you choose clockwise, you have to set the 'Rotation Angle' in DAVID as a negative value.
I have only used the first three scan positions for this example. The files are named as:
Opel2 0° (green), Opel2 45° (blue) and Opel2 90° (ochre). After uploading I have clicked on the button "Arrange visible scans in one row". The vertical line below each car is the axis of the turntable to carry the car. Often it's better not to put the object on the rotating disk but to extend the turntable axis and fix it there. See screen shot 1.
Starting with alignment:
Choose the 'Alignment' 'Around Y-Axis', set the 'Rotation Angle' = 45°.
Click on 'Align Scans'. Click on the first file 'Opel2 0°.obj', then click on the second file name 'Opel 2 45°.obj'. And voila, the first two scans are aligned, see the second screen shot (2).
Now I prefer to combine both to a "group":
Click with the left mouse button onto the first two file names by pressing the 'Shift' key at the same time so that the names are red shaded. Then click with the right mouse button on this red field, a new small window opens. Click with the left mouse button on "Combine selected scans". Result:
See screen shot 3.
Now set the 'Rotation Angle' to 90°. Click on 'Align Scans' and in the 'List of Scans' on '[Group]'.
Then click on 'Opel2 90°.obj'. See the result (after some seconds) on screen shot 4.
This was shown for only 3 positions. Continue your work in the same way, combine each time to a (bigger growing) group and after all positions are aligned, delete all unwanted things (like here the car holder) and then fuse them.
Hope all was explained correctly.
Walter
Edit: The final alignment after 'Alignment around an Axis' and the preset angle should be made by the tool "Pairwise Fine Registration". Maybe several times to achieve the best result. X56GHY.
- Attachments
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- David's coordinate system
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- Screen shot 1
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- Screen shot 2
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- Screen shot 3
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- Screen shot 4