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Edit Point Cloud in 3D

Use this dialog to edit point clouds or a selection of points in 3D.

This function is typically used to manually remove noise from ground scan data, such as trees, buildings, and other objects.

Where to find the dialog?

In the context menu in terrain model drawing, when a point cloud is selected on the screen, choose Tools - Edit Point Cloud in 3D...

Using the dialog

Open editing in 3D

Procedure

  1. Select the point cloud(s) in 2D view and choose Edit Point Cloud in 3D... from the context menu.
  2. Click two points on the screen (baseline), then dynamically adjust the height of the rectangle for the desired point selection.
  3. The program opens a separate window for editing the selected point cloud in 3D.

Dialog box for editing point cloud in 3D

The pixel size can be set during editing. This provides better visual interpretation of the data.

Example pixel size 1:

Point cloud with pixel size 1

Example pixel size 3:

Point cloud with pixel size 3

Point clouds have a dedicated application layer presentation rule called Point Cloud, with four different options for how points can be displayed on the screen.

If the intensity or height options are active in the drawing, you can select points based on the values of these attributes.

Using the intensity property to clean a point cloud is suitable when the noise has an intensity that stands out significantly from the rest of the point cloud.

Select points

Point cloud editing is a manual and often time-consuming process that can involve a lot of repetitive operations.

Several of the options in the dialog are therefore also available in the context menu with keyboard shortcuts so that unnecessary hand movements can be minimized.

Function Keyboard Shortcut
Select with polygon [Spacebar]
Reverse selection [X]
Delete [R]
Increase pixel count [E]
Reduce pixel count [Q]

Procedure

  1. Zoom/navigate to desired perspective.
  2. Use standard DDSCad selection function or polygon [Spacebar] as shown in the figure below.
  3. Selected points (the selection) get blue color on screen.
  4. Press [R] to delete these.

Navigation in 3D view

Select points with polygon

Selected points shown in blue

Select points based on intensity or height

Procedure

  1. Initial values are the minimum and maximum values in the point cloud.
  2. Change the values by manual entry (remember to click Update Selection afterwards).
  3. Change the values by pressing the arrow keys in the dialog, optionally change step value.
  4. Change the values by clicking on the screen (click Pick..., hold down [Shift] and select points as usual. The program calculates average value from the points).

In the example below you have two pipes attached to a rock wall. You can see that these stand out in terms of intensity and can therefore be easily removed.

Points with deviating intensity marked for deletion

Use other point clouds as background during editing

You can display point clouds from other application layers as background. These background point clouds are shown in gray and are not editable.

Before you select the function, you must also select point clouds in other application layers if you want to use these as background point clouds. The point clouds in the active application layer are the ones being edited, while those in other application layers are displayed as background.

Point clouds from other application layers shown as gray background

Overlapping points can be automatically selected in the editable point cloud either by proximity control or by 2D overlap.

Overlapping points

How the different options work can be illustrated more closely in the cross-section.

Cross-section showing overlapping points

Visualization of how overlapping points are selected with tolerance 1

Note

The size of the sphere is the median of all distances between the point and its 10 nearest neighbors, multiplied by the tolerance.

Cross-section showing 2D overlap

Note

In cases where not all overlaps are detected, the points must be removed manually.

Select points with standard DDSCad selection

You can select multiple points at once using a dynamic rectangle. Hold [Shift] and click the upper left corner of an imagined rectangle. Left-click and hold the mouse button. A rectangle with a dashed line appears. Drag the rectangle down to the right and release the mouse button when the desired points are inside.

Note that you must hold [Shift] when selecting points in 3D view (overrides rotation). If you want to add more points, hold [Ctrl] + [Shift]. Similarly, you can remove points from the selection by dragging a rectangle down to the left.