Support
Why does the selection shift when zooming or rotating?
Summary
Visual selections (by rectangle, circle or polygon) in TCP-PointCloud Editor are view-dependent: they carry no world coordinates, so when you zoom or rotate the view the outline stays fixed on screen while the cloud moves, and the final selection no longer matches the intended area. This article explains that this behaviour is intentional and how to work with it: select when you can see the area in enough detail, take advantage of selections being cumulative, use selection by outline with a closed 3D polyline (which is view-independent), and clear the selection polygons that are left behind.
Applies to
TCP-PointCloud Editor (POINTCLOUD). The documented cases do not state version numbers.
Point cloud selection functions: visual selection by rectangle, circle or polygon, and selection by outline.
Symptoms
During a rectangle or polygon selection, zooming or panning the view keeps the outline fixed on screen while the cloud moves, so the final selection does not match the intended area.
When selecting by outline and zooming in to see relevant areas, the polyline does not move closer or further away together with the cloud and the outline is no longer valid.
After the selection, drawn polygons remain and are not deleted.
Cause
View-dependent visual selections: selection by rectangle, circle or polygon has no coordinates; the shape drawn stays relative to the view and not to world coordinates. As this is a purely 3D application, in which the view orientation can be changed at any time, it is not possible to keep a fixed plane on which to project the selection outline. This behaviour is intentional by design, not an error.
Polygons that remain: when the selection is made in plan view, the selection polygons are kept on purpose so as to keep a visual reference of the areas already selected and to be able to select them again if required. They are stored on a drawing layer.
Solution
Case: the selection shifts when zooming or rotating the view
Make the visual selection (rectangle, circle or polygon) when you can see in enough detail the whole area you want to select, without needing to change the zoom while drawing it.
Take advantage of selections being cumulative: make one selection in one area with a given zoom and orientation, then another in a different area with a different zoom and orientation, and so on until the set is complete.
If you need a plan selection that is view-independent, first draw a closed 3D polyline (while drawing the polyline you can zoom) and then use selection by outline with that entity.
To remove the selection polygons that have been left behind, clear the drawing layer that contains them; doing so deletes all those polygons.
If the problem persists
If you do not get the expected result after following these procedures, contact Aplitop technical support stating the steps you carried out.
Category: Point cloud display and editing · Level: Intermediate