Graphical Interaction

  V2K provides structured mesh tools within a graphical user interface based on the MOTIF widget set. User interaction with the software is achieved via the mouse, keyboard, and working display.

  The working display is the graphics window within which all graphical rendering is performed. All rendering is dynamic in that the results of all operations with a graphic component invoked by the user are immediately displayed. Furthermore, in addition to the basic transformation operations attached to the mouse, the user may also interact with the collection of displayed objects with the specific manner of this interaction dependent upon the active facility.

Mouse Functionality

  Understanding mouse functionality within V2K is crucial for successfull interaction with the software. The individual functions are described below. Note that, in general, each of these functions remains active regardless of any other facilities which may be invoked.

Interactive picking

  Interactive picking, or the selection of one or more displayed objects, can be performed by simply positioning the cursor over the desired object witih the graphics window and then pressing the right-mouse button. Successful selection of an entity will cause it to become highlighted in red. Depending upon the current picking mode, the selected object(s) may placed within an internal working buffer for subsequent processing as might involve the assignment or modification of various attributes.

  If the active facility supports the selection of multiple objects for simultaneous processing (as for setting surface rendering characteristics), the user need only press and hold the Shift key while selecting the individual objects. Any selected object may be removed from the pick buffer by simply picking it a second time. Note that the Shift key must be depressed while each object is selected otherwise the paradigm reverts to the single object selection mode. Finally, all selections may be discarded by simply selecting NULL space (i.e. no object) in single selection mode. Lastly, the user should note that object(s) need not be visible to be currently selected; objects which are selected and subsequently "turned-off" remain selected. Null space should be selected to then clear the selection buffer.

  The Edit menu in the main menu bar provides a picking shortcut if it is desired that all of a certain class of entity are to be selected. In addition, the selections available within this menu provide for a limited granularity in that selection of members of a particular class of entity may be dependent upon their current state. The facilities in the Edit menu are described more fully below.

Scene Panning

  The mouse enables the user to pan the scene within the graphics display by simply pressing the left-mouse button and then moving the mouse. The displayed objects will move in the direction in which the mouse is moved. Note that the left-mouse button must remain depressed and the mouse remain in motion for the displayed objects to stay in motion.

Scene Zooming

  Scene zooming is performed using the middle-mouse button. Simply press and hold the button while moving the mouse up or down to zoom the scene. An upwards movement of the mouse will zoom out, and a downwards movement will zoom in. The center dot provides a visual reference point about which the zooming will occur; any point positioned at the center dot will remain so positioned for any zooming. This point represents the center of the screen fixed axes about which the zooming is performed.

Scene Rotation

  Scene rotation can be performed in two ways. Standard rotation is performed by pressing and holding the Shift key and with the left-mouse button depressed, movement of the mouse produces a rotation about a set of screen fixed or world axes. The extent and speed of the rotation are dependent upon the cursor location and the direction and speed of mouse movement. Rather than quantify the paradigm, the user is best advised to experiment with this mode until an intuitive "feel" has been developed.

  Alternatively, the geometry may be rotated directly about body-fixed axes using the Ctrl key. With this button depressed, the view will be rotated about a single invariant axis based on the choice of mouse button. The left-, middle-, and right-mouse buttons produce rotations about the x-, y- , and z-axes, respectively. Note that in this mode, the picking functionality tied to the right mouse button is temporarily suspended.

  Though either mode produces a rotation only as the mouse is moved, the spin momentum option may be activated if rotation rates are desired to persist even after the modifier key and mouse button released.