PIAS Manual  2021
Program for the Integral Approach of Shipdesign
Wireframe points

Wireframe points represent the connecting vertices in a boundary representation, see A brief introduction to topology and connectivity of solids. This action, which is started from the menu [Objects]→[Wireframe Points] or with the keys <Alt><O><P>, makes it possible to

Since wireframe points can also be created implicitly where curves meet or intersect with Wireframe connections, the purpose of this panel is mostly sketching, marking and labeling particular coordinates, and removing wireframe points (and their connections) that are not desired.

Contrary to ordinary points in Fairway, which are features of curves, wireframe points are features of a wireframe. Wireframe points are differentiated optically from curve internal points and knuckle points with a bigger marker, so that they do not obvuscate ordinary points when they are displayed at the same time.

action_wireframe_points_600.png
Manipulation of wireframe points (vertices).

Note that it is possible for a wireframe to exist without wireframe points — a newly imported DXF or IGES wireframe will not have wireframe points, which means that curves are unconnected and without structure. Curves can only connect through wireframe points. Wireframe points are essential in the conversion from a wireframe to a solid: they define the topology of the wireframe, giving information on which curves are connected where. Strictly speaking, a solid also has B-rep vertices or wireframe points, but in a solid their connections are permanent and are therefore hidden from the user.

A wireframe can also exist without curves and purely consist of wireframe points. This can occur after the import of a point cloud or manual definition of a point set, with the intention of constructing wireframe curves through the points afterwards. Another application of a wireframe in Fairway is just to group freestanding points and curves in support of ordinary solid modeling, to mark important positions and shape features, without the need to be part of a boundary representation. Such a wireframe would just be for marking geometric information, be it temporarily or permanently, and never be converted to a solid. The ability to label wireframe points can be a practical feature in this use case.

Move wireframe points

When the [Move] button is depressed, the position of wireframe points of active wireframes can be changed, either by dragging or with the keyboard after pressing <F2>. If there are any curves connected to the wireframe point, these curves are faired through the new position, and the available axes of motion are constrained to the planes in which connected polycurves are defined.

Label wireframe points

As an added feature, wireframe points can be labelled with a name. The names will be added as a graphical annotation to the wireframe points after the action is applied.

If there are many points present in a wireframe, the list can be long and unordered. It may therefore be most practical to depress the [Move] button and identify the point graphically, which will bring the corresponding row in the list into focus. Then press <F2> to start editing, and press <Tab> to proceed to the [Name] collumn.

Delete wireframe points

Wireframe points can be deleted when the [Delete] button is depressed. Obviously, this will disconnect any curves that were connected to it. Pressing <Ctrl+A> will remove all wireframe points in all active wireframes.

Add new freestanding wireframe points

If curves are present, one would most frequently be interested in adding wireframe points where curves should connect. For that, another action is more appropriate, see Wireframe connections. But when a new wireframe point must be added that is freestanding and unrelated to curve intersections, this can be accomplished with this action when the [Add] button is depressed. The position of the prospective wireframe point can be dragged with the dragger, or typed in as the last item in the list. The point will be added when the action is applied.