Cloudcompare - point cloud slice

1. Section extraction function

   Use Tools > Segmentation > Cross Section Access this tool .

   This tool allows users to define clipping boxes around a given cloud （ Interactive or non interactive ）. for example , You can adjust the range and direction of the box to split the cloud . Besides , The tool can also ：

• The process of repeating segmentation in one or more dimensions （ Extract multiple for the instance “ section ”）
• Extract polygon contour in each slice

   Select a point cloud and start the interface of the tool as follows ：

It should be noted that ： The initial crop box here （ That is, the yellow line in the figure ） It is the bounding box of point cloud

Edit crop box ：

   You can edit the crop box in various ways , You can drag the bright red in an interactive way , Green and blue arrows and rings , Directly in 3D Move the boundary of the clipping box in the view . The arrow tip is used to push and pull the cutting frame surface , The ring can be used to rotate the box around the arrow axis . The lower left corner （ yellow ） The interactive device of can be used to move the whole box .

   The following buttons in the upper right corner can cancel or display the clipping box and arrow .

   You can also use “X”,“Y” and “Z” Field directly edit the size of the clipping box （ Width , Depth and height ）. You can also use the buttons at the bottom of the dialog （“Shift box” frame ） Move the box in all directions . The box will move by the same amount as the box width in this dimension . Last , If more control is needed , You can click “advanced” Button . Will appear “ standard ”3D Box version dialog .

Set the box position in the space in various ways （ for example , Even force the box to be a cube ）.

visualization ：

   You can adjust the view with one button

2. Extract a single slice

   Click the following button , Points in the clipping box can be extracted .

3. Extract a single contour

   Click the following button , Extract the boundary contour .

   The main parameters and functions are as follows

Necessary parameters

• flat dimension： Plane size , Automatically set according to the current section size
• maximum edge length： Maximum side length , As a result of “ Concave bag ” Algorithm extracts contour . The only parameter of this tool is that of a single edge “ Maximum size ”. The algorithm starts with the convex hull of the slice point . As long as the edge is longer than the specified “ Maximum length ”, The algorithm will try to segment it using another nearby point . In this way, the outline will be closer to the point cloud . So the smaller the parameter is , The tighter the contour .

The other options

• project slice(s) points on their best fit plane: Contour extraction is in 2D Finished in the plane ,CloudCompare The slice plane size is not used as the projection plane , Instead, the point is projected onto the best fit plane （ This is for very thick slices , It usually works better ）.
• split contour(s) on longer edges:：CloudCompare Can be longer than at each edge “ Maximum side length ” Parameter when dividing contour . under these circumstances , You can generate multiple non closed polylines instead of a single closed contour .
• visual debug mode: Used to display debugging results .
  

4. Extract multiple slices

   The button shown in the figure below is to realize multiple slice extraction

   Most of the parameters in this dialog are related to “ Extract a single contour ” The dialog box is the same .

   however , The user must clearly specify whether he wants to generate the contour （ Choose “Extract contour(s)” Check box to enable ）. Otherwise, only slices will be generated .
Other parameters are ：

• Repeat dimension: Set the extracted latitude （ By default , Only check “ Plane ” dimension ）.
• Gap: Gap distance between adjacent slices .

The specific operation is as follows ：

5. Related codes

[1] PCL Convex polygon boundary extraction of plane point cloud
[2] PCL Concave polygon boundary extraction of plane point cloud
[3] PCL Point cloud slice
[4] Open3D Point cloud slice