Working with Point Clouds (V19)

Command: PointCloud,  PointCloudAttach,  PointCloudBoundary,  PointCloudColorMap, PointCloudCrop, PointCloudPointSize, PointCloudPointSize_Minus, PointCloudPointSize_Plus, PointCloudPointMax,  PointCloudPreprocess, PointCloudUncrop,  PointCloud2dVsDisplay

Overview: In this article, you learn how to use point clouds in BricsCAD.

1. Prepare the data into the right format using preprocessing.

2. Attach the prepared data to a drawing in BricsCAD.

3. Use the drawing with the points, eg as a blueprint to start a drawing.

Preprocessing

File types supported: .las .pts .ptx.

To be able to navigate large point cloud datasets quickly, its data must be preprocessed. Use the command POINTCLOUDPREPROCESS. This opens a file dialog that lets you select input point clouds.

The next step is to select the name of the preprocessed output file. By default, the file dialog suggests the same name of the input file (without numbers before the extension). This name can be modified. The file type is .bpt (Bricsys Point Tree).

For AutoCAD® users: This is the equivalent of creating a .rcp file in Recap.

Attach to a drawing

Use the command POINTCLOUDATTACH to attach the preprocessed .bpt file to the current .dwg file.

Note: A point cloud can NOT be attached to an empty template. The .dwg has to be saved first. This is because the attached point cloud uses a relative path.

When the .bpt to be attached is selected, a dialog appears. This allows the user to specify how to insert the point cloud into the drawing.



Figure 1: point cloud attach dialog. Here the user gets the possibility to choose how the point cloud is to be inserted in the drawing.

Options are:

• Insertion point

• Scale

• Rotation

When the checkbox "specify on screen" is checked, an insertion box will appear to let the user determine translation/rotation/scaling whilst placing the point cloud on the drawing. For the other options, the values in the dialog boxes will be used.

Procedure: Manipulate point cloud in .dwg

Once the point cloud is attached, it can be manipulated like other entities. Moved /rotated/scaled using the Quad. It also responds to section planes.

Use the command SECTIONPLANE to hide parts outside section planes (Figure 2).

Note: A section plane has three states:

• Plane: Clip everything away at one side of the plane.

• Boundary: Define an infinite extrusion of the contour drawn on the screen.

• Volume: The same as Boundary, but with a given top and bottom plane.

Figure 2: A point cloud with a section plane (inner blue cuboid). In red: the section plane Properties panel. The section plane state is set to "volume".

Snapping to visible points in the cloud is also possible. Turn on endpoint and/or midpoint, to snap to points on a point cloud.

Drawing Explorer

Figure 3: An example of the Drawing Explorer for point clouds.

The Drawing Explorer also supports point clouds, in particular the definitions of the point clouds attached to a dwg. When receiving a dwg and a point cloud of which the path cannot be referred correctly on your computer, it is possible to adjust the path for the point cloud there. The Drawing Explorer can be found via the GUI menus or via the command PointCloud

Properties panel

Figure 4: A point cloud in BricsCAD. In red left, the point cloud Properties Panel is shown. This panel appears when the point cloud is selected.

When clicking (and thus selecting) a point cloud, its properties become available in the properties panel. From there, properties like insertion point, rotation, scaling, colormap, ... can also be adjusted.

Other functionalities

• Colormap (POINTCLOUDCOLORMAP): False colors can be assigned to the points corresponding to intensity or elevation. Choose single spectrum colors such as red or blue, or go the whole spectrum.

Figure 5: some examples of colormaps in function of the point elevation. The left part has colormap "Spectrum"; the middle part colormap "Hydro" and right part has colormap "Earth".

• Cropping (POINTCLOUDCROP): Crop only the current point cloud, leaving other entities unaffected. A section plane crops everything in the scene.

• Point Size (POINTCLOUDPOINTSIZE): Change display size of points. (Can be useful to make virtually fill in gaps.)

• Maximum number of points displayed (POINTCLOUDPOINTMAX): Change the maximum number of points displayed. Since a computer screen has only a few million pixels, it makes no sense to display billions of points at the same time. This parameter sets the maximum for the number of points to be shown at any given instance on screen. Make no mistake, the actual point cloud can be many times larger than this (easily a few hundred million points and more).

• Boundary (POINTCLOUDBOUNDARY): Show or hide the point cloud bounding box.

Figure 6: point cloud has been sectioned and the left image shows the point cloud with boundary whereas the right image shows the point cloud without boundary. 

AutoCAD® compatibility

AutoCAD® can open and use the .dwg with the same point cloud, clippings and other entities present in the drawing. When the user also has AutoCAD® and Recap, save the Recap preprocessed, point cloud file in the same location with the same name as our .bpt file. The extension will be different (.rcp).