Central to the development of an end-user 3D
modeling/rendering application program is the ability to interactively select objects or
polygons using a mouse-click or via a fenced rectangular region chosen by a user. Such a
mechanism was developed for Okino’s "NuGraf" product and
is now available in the "Application Builder" version of the NuGraf Toolkit.
This picking mechanism is one of the most interesting and useful implementations available;
it draws on the best features of the picking mechanism from the two
top-named 3D modeling packages, namely SoftImage® and Alias® . It can pick by
mouse click (using an internal ray tracing algorithm), by fenced region, by instance name
or by material name. The interesting aspect of this mechanism is that it can automatically
pick a child, a branch or a portion of the instance tree through the use of the
toolkit’s hierarchical database manager. For example, if the current picking method
is set to ‘branch’ and the user clicks-on or selects the ‘Empty Instance
#2’ shown in the diagram above, then all instances below ‘Empty Instance
#2’ will automatically be selected. Complete picking state information is maintained
by the hierarchical database manager and is available at all times to the host program.
