Point Cloud Editing Tutorial

Editing the attribute information on point clouds is an important step in LIDAR data processing and complements automatic classification schemes such as object identification by machine learning. This tutorial covers the aspects of manual corrections of point clouds (though by virtue of the underlying fiber bundle data model, any kind of data can be handled same).

To get started, download the data file EditingTutorial.f5 (32MB) for this tutorial (as available from the HydroVish Download Page. This file contains a partially classified point cloud. Load this file into HydroVish, and extract a Grid as described in the fiber bundle introduction. You may now set up a visualization first, or proceed towards setting up editing right away and set up the visualization afterwards.

Setup Visualization

Select Display/HeightDots from the Grid and press the space key for centering the view.

Quick Step Instructions:

Load File
Use [F] button, create Grid object
Use [D] button from the Grid object, create HeightDots visualization object
Press space bar for centering the view.

Note that the HeightDots module will also create a Colormap module, which is used for the default colorization of dots according to their height. This module can be hidden right away such that it is out of view and does not clutter the network (just hide it, but don't delete it).

Use the mouse to navigate around for a pleasant view. The size of the dots for this point cloud may be too large (but is a matter of personal taste). To adjust them, increase the Expert Level setting of the HeightDots module to 1 by clicking on the right half of the expert level display frame, which shows "[0]" initially. A "sizescale" parameter will show up. Set this to 0.2, or whatever looks appropriate. Note that at any stage you can save the current visualization network to a script file, preferably using the CTRL-S shortcut, such that settings can be restored from it.

Setup Labeling

Go to expert level 2 in the HeightDots module and right-click on the input field of the FieldVisibility, i.e. the red text there. Create Classification/Labels via the context menu. Double click on the input name FieldVisibility such to expand the input. This input field should then look like this:

Now, set up the various classes for the labeling, starting by clicking the [+] button to add a new entry. Edit the text field for an arbitrary text, followed by the classification number in parenthesis such as (34) to reference points with numerical attribute 34. Right-click on this text field to edit the color associated with this class - any modification will be visible immediatedly in the point cloud display. The demo data set uses the following classes:

Of course, be welcome to use different colors and play with the various input parameters for the HeightDots display module such to optimize the rendering according to personal taste. It is recommended to safe the network frequently (CTRL-S) such to preserve a favorite setting.

Setup Editing

From the Grid object, extract the Fiber/Classification field. From the newly created Classification field, create a Edit/MaskedLabels (available from the Edit category button "✍"). Right-click on the labels input name of the newly created MaskedLabels and select Attach Parameter from the context menu. It will provide one option directing to => Labels_for_HeightDots.labels. Once this attachment has been established such that the MaskedLabels object has recognized the same label set as input (double click the input name to see the labels also directly within the MaskedLabels object), it will display two more columns of input buttons to the right side:

The first column of new button selects which class will be used when assigning values to points (only one can be selected), the second column of new buttons selects which classes are editable at all. The visibility buttons on the very left side determine whether classes can be used at all; points with inactive classes will be invisible and cannot be selected (however, if a class is selected and marked editable, it will remain at this status even if later set to inactive - it is left to the user to decide whether this mode of working is useful).

On the labels enable the "editing" property for those classes that may be modified, and select one class that shall be used for assigning points.

Find the Lasso object in the network, an select draw mode. Click at the point cloud to draw the outline of a polygone for a shape to be marked for editing. The top toolbar provides Undo/Redo buttons for the drawing operation using the Lasso.

draw mode allows to modify the shape of a polygon.
active mode allows to apply an existing shape to the current mouse position; clicking left mouse moves the polygon, keeping the left mouse button down and moving the mouse drags the shape around.
inactive mode re-enables the left mouse button for 3D navigation

Once a polygonal shape (the "Brush") looks satisfying, push the [Select] button in the MaskedLabels object. All points that fit the editing criteria will show up in bright red now.

Note that MaskedLabels's [select] button can be attached to => Lasso.finishAction - this setup is useful in conjunction with Lasso's active mode. Alternatively, MaskedLabels's [select] button can be attached to => Lasso.finishDrawing, which is useful if points shall be marked right after drawing a polygonal outline. Both actions may be repeated as much as needed, with "Mask Undo" and "Mask Redo" buttons available under the toolbuttons, as well as a "Clear Mask" button for clearance (cannot be undone).

Once the masking of the points looks fine, push the [applySelection] button to actually change the classification information for the point cloud. There are tool buttons for Undo/Redo of this operation as well. Another setup is to attach MaskedLabels's [applySelection] button to => Lasso.finishDrawing, which allows to immediately modify the points from drawing the selection outline.

Practical Remarks

To actually stored any editing operations, rename the input file from "EditingTutorial.f5" to "EditingTutorial~.f5". Only with an extension "~.f5" edits will be forwarded to the file, otherwise they remain in memory - which is good for learning and experimenting with the capabilities, but in real work changes need to be persistent.
Use the "importance view" feature to simplify the GUI by clicking the button on the respective input slot of interest. The "iView" tab will then show only those input parameters that have been set as "important".
To restrict editing to a subset of the entire data, using a constraining the spatial region for editing is possible.
An existing network can be reused with another input file name, it is not required to rebuild the visualization networke each time. The Bundle object offers to enter another filename at expert level 2, as well as a reload button.
The file name can also be specified as argument when invoking HydroVish binary by overriding the name of the involved Bundle object in the script, e.g.:
```
      hydrovish.exe EditingTutorial=more.f5 myscript.vis
    
```

For an overview of all VISH help topics see the Table of Contents.