User Manual for Subsetting Within SFA

James Hall

University of Regina

July 23, 1998

SFA has a powerful subsetting feature, allowing the user to eliminate areas not of interest, as well as to reduce overall glyph counts in order to speed rendering times. This document is a user manual outlining the features and mechanisms of this subsetting feature.

4: Manipulating Existing Subsets

1: Introduction

SFA's subsetting functionality provides the user with the capability to define multiple 3-dimensional rectangular areas of interest. When any subsets are defined, no glyphs outside of the defined subsets are rendered to the screen, or are used for features such as Contour plates.

If a subset overlaps a portion of any other subset, a high definition area is created. Non overlapped areas will have one in every five glyphs drawn, while overlapped areas have all glyphs drawn, providing the user a mechanism to selectively view areas of interest.

Subsets are displayed as semi-transparent gray cubic volumes, fully within the boundaries of the main set volume. When not being created or edited, the subsets are not drawn in the main window. However, the user can still see the existing subsets within the subset thumbnails.

2: Subset Thumbnails

Each subset has an associated thumbnail -- a small window on the right side of the main window, indicating the size and position of the subset. These thumbnails are also used to popup sundial menus to perform extra operations on the subset displayed.

3: Creating Subsets

Subsets are managed in SFA using the nose button of the right-hand bat (the nose button is the button farthest away from the wires). Subsets are swept out by depressing and holding the nose button, sweeping out the desired volume, and releasing the button. Additional subsets can be created immediately by repeating this action. Currently, the maximum number of subsets that can be active at any time is 8.

The only restriction to the subset being swept out is that the volume cannot extend beyond the volume boundaries. Should the user extend the cursors beyond a volume boundary, the subset will go up to the boundary, but not beyond.

4: Manipulating Existing Subsets

In addition to sweeping out new subsets, existing subsets can be edited (resized), redrawn (re-swept out), and deleted. These operations are initiated by the use of a sundial menu. By positioning the right cursor over a particular subset's thumbnail and pressing the nose button on the right bat, a sundial menu is brought up with four options: New, Edit, Redraw, and Delete. This sundial is drawn using a dark background colour and light text to distinguish it from the main sundial menus used in SFA.

Once each manipulation is complete, the scene is redrawn using the new subsetting information to decide which glyphs should be drawn.

4.1: New

The New option on the subset sundial menu provides a mechanism for the user to get out of the resizing and redrawing modes and back into the standard mode, where pressing the nose button will initiate the creation of a new subset. Selecting this option when already in this standard mode performs no operation.

4.2: Edit

The Edit option on the subset sundial menu provides a mechanism for the user to resize an existing subset. Once this menu option is selected, the user is placed into a 'resize' mode. Once activated, this mode causes the subset to be drawn in the volume. In this mode, as the user moves the right cursor around the volume, the nearest face of the subset volume to the cursor is highlighted in yellow.

When the user presses the nose button while in Edit mode, the highlighted face is manipulated by the movement of the right cursor. The face can be made larger or smaller, or the entire face can be moved (making the volume larger or smaller). The shape will remain rectangular, and the resized volume again must remain within the boundaries of the main set volume.

4.3: Redraw

The Redraw option on the subset sundial menu provides a mechanism for the user to erase the current subset, and sweep out a new one in it's place. Once in this mode, the user positions the cursor at the start location of the new subset, presses the nose button, and sweeps out the new set. The old set is removed, and the new one is created.

4.4: Delete

The Delete option on the subset sundial menu provides a mechanism for the user to completely remove the current subset. The subset and it's associated thumbnail are removed.