Copyright Goodheart-Willcox Co., Inc. Chapter 15 Point Clouds 411 cuts through a point cloud and then extract 2D geometry from the resulting section boundary. These methods are discussed in the following sections. NOTE NOTE Hardware acceleration must be enabled in order to work with point clouds. For optimal results, make sure your computer’s graphics card is updated with the most current drivers installed. Point Cloud Drawing Aids and Construction Tools As with other types of 3D model surfaces, you can orient the UCS to a planar face in a point cloud for construction purposes. Use the Object option of the UCS command to orient the UCS to a surface in the point cloud. Once the UCS is properly oriented, use standard 2D and 3D drawing commands and object snaps to create new geometry. AutoCAD provides object snaps for accurately selecting points in a point cloud. Point cloud object snaps assist in creating new geometry and taking measurements of existing features. The available point cloud object snaps are Node, Intersection, Edge, Corner, Nearest to plane, Perpendicular to plane, Perpendicular to edge, and Centerline. These are set in the 3D Object Snap tab of the Drafting Settings dialog box, introduced in Chapter 1. NOTE NOTE In order to use some of the point cloud object snaps available in AutoCAD, the point cloud must contain segmentation data. Segmentation data is obtained by identifying groups of neighboring points that make up the same planar or non-planar surface. Segmentation data is processed when scan fi les are indexed in Autodesk ReCap Pro. Accurate processing of segmentation data is dependent on the type of laser scanner used and the work that is scanned. To determine whether the point cloud contains segmentation data, select the point cloud, open the Properties palette, and check the status of the Segmentation property in the Misc category. Another way to orient the UCS to a planar surface on a point cloud is to use a dynamic UCS. Dynamic UCS behavior when detecting a point cloud surface is similar to that when working with solid models. Hover the cursor over the appropriate surface to align the XY plane with the surface and then draw the new object. When the command is completed, the UCS reverts to its previous location. In order for the dynamic UCS function to work correctly, make sure to turn off 3D object snaps before hovering over the desired surface. Extracting Geometry from Point Clouds You can generate new 2D geometry from point clouds by using extraction commands to copy or “extract” objects from existing surfaces. You can extract edges of planar segments, corners of planar segments, and centerlines of cylindrical segments. The new geometry is created on the current layer and can be modifi ed in the same way as other 2D objects. The PCEXTRACTEDGE, PCEXTRACTCORNER, and PCEXTRACTCENTERLINE commands are used to extract geometry from point clouds. These commands are accessed in the Extract panel in the Point Cloud contextual ribbon tab. Refer to Figure 15-8.