3rdTech SceneVision-3D Manuels rapides - Page 5

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IV Range Alignment with SceneVision-3D
You have SceneVision running, a scene open with multiple scans from different tripod locations, and are ready to do range
alignment. Make the window large.
1. Select the Range Align tab. Then select the 1:New button.
2. Choose a file to base the alignment on. If no files are aligned, choose a reference or large scan. Otherwise, choose an aligned file that overlaps
the file you want to align.
3. Choose a file to align. It must be a file that overlaps the previous selection. Windows for both files will open.
4. Go the Window menu and choose Tile Vertically. (Not required, but makes it easier to work.)
5. Your goal is to select 4 to 6 pairs of correspondence points. The Create Correspondence Point button is already selected.
Zoom out to identify locations where you can find correspondence points. Zoom in to make the selection.
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Select a point in one window (it doesn't matter which one) by holding Ctrl and picking with the mouse. Then select the
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corresponding point in the other window.
Repeat 4 to 6 times.
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Note: The program uses the points as starting points only, so they should be good but need not be perfect.
6. Select the 2:Calc button. It will calculate the alignment. Errors below 0.3" are very good and below 0.5" are desirable.
7. Select 3:Apply. This aligns the file and a ruler appears next to the filename in the scene tree.
8. To do a quick check of the alignment, select the Show button. This will create a temporary 3D model of the two files.
Look at the overlapping walls and edges of objects. Make sure they are 'very' close.
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9. If it looks good you're done. Save the scene with the save button and it will save all the correspondence points and the alignment.
10. If you're not satisfied you can move any of the current points and/or add additional point pairs.
Note: Make sure both points of a pair are on the same surface – not one on a surface in front and the other on a
surface behind.
To move a point, select the arrow cursor, hold Ctrl, and drag the point to a new location.
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To add a point, select the Create Correspondence Point button and then repeat step 5 above.
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Note: Try adding points on a different surface.
11. After adding or moving points repeat steps 6 - 9.

Tactical Tips

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The key to good alignment is good scanning! Make sure you provide plenty of overlap when scanning. Scanning an extra 90° takes
only a couple of extra minutes – but can make a big difference when doing alignment. (And you don't need to include the extra
data in your model.)
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When choosing points to align, avoid the outside edges of objects, like furniture. It's difficult to see if those points are on the object
or on the background. Instead, choose 'interior' points or corners that are visible but are not on the edge.
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Choose points that are not all in the same plane – from different walls, the floor and ceiling, and object surfaces – whenever
possible.
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The order you do alignment doesn't matter. Also, alignment between and two overlapping files will work. For example, you can
align Scan A to B, A to C, C to D and D to E and everything will be aligned. There just needs to be a link.
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Sharing Alignment: Sometimes 2 files should have the same alignment. For example, fileA.rtpi might be aligned, and
fileA_color.rtpi – the same file with color - might not be aligned. You can fix this easily – without redoing the alignment.
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Insert the color file into the scene if it is not already there.
Select both files in the scene tree (one aligned and one not aligned).
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Select Align->Share Alignment with from the Edit menu.
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You can also remove alignment from a file with Align->Clear Alignment in the Edit menu
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DeltaSphere-3000 3D Scene Digitizer
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9/23/05