Online Help Reconstructor 4.4

The 3D mesh selection works with an input mesh, a 3D polyline and a viewpoint that can be defined by an orthocamera, by a plane or by the current view.

The polyline, seen by the input viewpoint, determines a frustum that intercepts the mesh defining a portion of it. This portion is acquired by doing Virtual scan, and uniformly meshing the resulting grid point cloud. The virtual scan is always done with an orthocamera that Reconstructor® creates internally.

When selecting the polyline and the viewpoint, the user doesn't need to check whether the polyline is contained in the orthocamera's frustum, or how the polyline is positioned with respect to the plane. Reconstructor, in fact, creates an orthocamera whose frustum is automatically enlarged to include all the polyline. This automatic expansion, however, does not take into account the mesh (this is done to fully exploit the orthocamera's resolution on the selection region).

The resolution of the internal orthocamera is calculated proportionally to the input mesh's vertices amount, so that the scanning is precise enough to preserve the input mesh's features.

If a plane is given as input, Reconstructor® creates an orthocamera that points in the plane +Z direction. If the polyline and the mesh are in the -Z semispace, they will be included anyway in the selection because the orthocamera will have a negative near plane. However, the direction of the plane (or of the orthocamera) influences the winding direction of the mesh that results from the selection.