Glossary

tr. v. The process of temporarily disabling clipping to one or more clipping planes, when it can be determined that the image doesn't cross these planes. By avoiding unnecessary time spent in the clip processor, adaptive clipping enhances performance.

n. An ancestor of a segment is a segment that refers, either directly or indirectly, to a given segment. If segment 1 contains a call_segment element referencing segment 2, and segment 2 contains a call_segment element referencing segment 3, both segments 1 and 2 would be ancestors of segment 3. Segment 2 would also be the parent segment of segment 3. Compare descendant.

n. A collection of data defined by and for the application. The Starbase Display List supports the storage of application data in the display list and allows retrieval of that data. The Starbase Display List does not process or evaluate the application data in any way.

n. A user-definable, 3D rectangular-solid volume of MC space. Display List allows you to specify such a three-dimensional volume and, during display traversal, compare the bounding box's dimensions with the currently active clip limits and cull size. The prune condition and the cull condition are then set to the appropriate values, and the application can test the conditions and respond accordingly. Pruning and culling can enhance performance significantly.

n., tr. v. The referencing of a segment by a call_segment, cond_call_segment, execute_segment, or cond_execute_segment element. These elements cause traversal of the referenced, subordinate, segments. A call is also referred to as a segment reference.

See hit-checking function.

n. A child segment is a segment that is directly called by another segment; it is a descendant that is exactly one level lower in the hierarchy (sometimes called daughter segment). Compare parent segment, and see also ancestor and descendant.

tr. v. The process of rendering inaccessible (either temporarily or permanently) a display list or one of its segments. Contrast open.

tr. v. Avoiding the display of a section of a display list if its representation on the display is smaller than some user-defined threshold.

n. The element at which the element pointer of a given segment points. Each segment has a current element that is retained across segment opening and closure. The phrase "the current element" means "the current element in the currently open segment."

n. The name set associated with the current element during traversal. The current set is used with filters. See also name set and current element.

See child segment.

n. A descendant of a segment is a segment that is referred to either directly or indirectly by that segment. If segment 1 contains a call_segment element referencing segment 2, and segment 2 contains a call_segment element referencing segment 3, both segments 2 and 3 would be descendants of segment 1. Segment 2 would also be a child segment of segment 1. Compare ancestor.

adj. Refers to a display list that is associated with a particular display device. That is, the gopen statement's 〈path〉 and 〈driver〉 parameters specify the device on which to display the contents of the display list. Contrast device-independent.

adj. Refers to a display list that is not associated with a particular display device. That is, the gopen statement's 〈path〉 and 〈driver〉 parameters specify "〈dev〉/null" and "display_list", respectively, and the associated display list can be displayed on any active display device. Contrast device-dependent.

tr. v. The process of drawing an image by traversing a device-independent display list. Compare refresh.

n. A collection of retained graphics and other data, grouped together in a hierarchical arrangement of segments, for manipulation and display.

n. A Starbase device whose sole purpose is to manage a display list. The display list device is not associated with any graphics input or output device. The Starbase device driver for the display list device is

〈common〉/lib/libdddl.a

and the name of the device driver (used in calling gopen) is "display_list". When the display list device is gopened, the path parameter must be "〈dev〉/null".

n. An element that can be used to mark a position in a segment. Display list labels can be used for element pointer positioning using the set_ele_ptr_relative_to_label function. Display list labels are one component of the path returned from the picking operation.

tr. v. Editing refers to those operations that modify the contents of a segment. This is also known as segment editing.

n. The smallest unit — the "atom" — of graphics data that makes up the contents of a segment. Elements correspond to Starbase and Display List functions; each function has a one-to-one correspondence with an element.

See Null Element.

The ability to control the visibility and/or pickability of individual elements in a display list.

n. The element pointer identifies the position within a segment for traversal, insertion, and deletion. The element indicated by the element pointer is called the current element. Element traversals take place by executing the current element; insertions take place after the current element; replacements take place at the current element; deletions begin with the current element.

tr. v. The act of moving the element pointer, which, as a result, changes the current element. The following functions perform element pointer positioning operations: set_ele_ptr, set_ele_ptr_relative, set_ele_ptr_at_end, and set_ele_ptr_relative_to_label.

n. Either the invisibility exclude set, the highlighting exclude set, or the unpickability exclude set. A name set in which "1" bits specify names which are to be excluded from the filtering process. A "1" bit in an exclude set overrides a "1" bit in the corresponding include set.

n. The rectangular-solid volume of MC space enclosed by the bounding box. Use for culling and pruning.

n. A Display List concept that allows the user to selectively prevent primitives from being displayed (the invisibility filter), disallow them from being picked (the unpickability filter), or cause them to be highlighted (the highlighting filter). Filtering uses the concepts include set, exclude set, and current name set.

n. A name set specified in the "exclude" parameter of the Display List routine set_highlighting_filter. Sections of the display list not to be highlighted are identified in this set.

n. The filter that controls primitive highlighting. The filter has two components: a highlighting include set and a highlighting exclude set, and these are compared with the current name set. This filter is defined by the set_highlighting_filter routine, and interrogated by the inq_highlighting_filter_sizes and inq_highlighting_filter routines.

n. A name set specified in the include parameter of the Display List routine set_highlighting_filter. Sections of the display list to be highlighted must be identified in this set.

n., tr. v. A hit occurs during a picking operation when a pickable primitive falls within the pick aperture.

n. A function used to determine whether or not a certain hit, during a picking operation, is acceptable.

n. Either the invisibility include set, the highlighting include set, or the unpickability include set. A name set in which "1" bits specify names which are to be included in the filtering process. A "1" bit in an include set is overridden by a "1" bit in the corresponding exclude set.

n. During element manipulation within a segment, insert mode is the default mode. Thus, elements will be added to, rather than replace, the other elements in the open segment. Contrast replace mode.

n. A name set specified in the "exclude" parameter of the Display List routine set_invisibility_filter. Sections of the display list to be excluded from visibility filtering are identified in this set.

n. The filter that controls primitive visibility. The filter has two components: an invisibility include set and an invisibility exclude set, and these are compared with the current name set. This filter is defined by the set_invisibility_filter routine, and interrogated by theinq_invisibility_filter_sizes and inq_invisibility_filter routines.

n. A name set specified in the include parameter of the Display List routine set_invisibility_filter. Sections of the display list to be made invisible must be identified in this set.

n. Conceptually, a name set is an array of bits; logically, a name set is contained in an array of integers. Names ("1" bits in the array) are used to identify sections of a display list for invisibility, unpickability, and highlighting filtering.

n. A system-defined, undeletable element at the beginning of every Display List segment. This special element of a segment comes before the first user-defined element of the segment (if any). When the element type of this element is inquired using inq_ele_type, a value of OP_NULL is returned. Positioning at element 0 allows insertion before the first user-defined element of a segment. Also called Element 0.

tr. v. The process of creating and/or causing to be accessible a display list or one of its segments. Opening must be done before operations can affect it. Contrast close.

n. A parent segment is a segment that calls another segment; it is an ancestor that is exactly one level higher in the hierarchy. Compare child segment, and see also ancestor and descendant.

n. The region of interest for picking operations. Primitives that fall within this region during picking operations generate hits. In 2D, the region is a rectangle; in 3D, a rectangular solid. Specified via set_pick_window and set_pick_depth.

See unpickability exclude set.

See unpickability filter.

See unpickability include set.

n. An identification of a branch of a segment network. There are three components of each item of a pick path: segment name, display list label, and offset.

n. A switch indicating whether the pick filter is a "pickability" filter or an "unpickability" filter. By default, it is an "unpickability" filter.

tr. v. A means of identifying a branch of a Display List segment network via graphical input. The function pick_from_segment performs this operation.

tr. v. The process during display traversal of avoiding those sections of the display list which would be outside the clip limits. This is a performance-enhancing feature.

tr. v. The process of drawing an image by traversing a device-dependent display list. Compare display.

n. When the display list is in replace mode, the current element of the open segment is replaced with any new element to be added to that segment. Once the element has been replaced, replace mode is exited and the default mode, insert mode is reentered. Replace mode is set by replace_ele.

n. The main unit of graphics data organization in a display list. Segments contain zero or more elements, in addition to the null element.

The ability to control the visibility and/or pickability of individual segments in a display list.

tr. v. Segment editing refers to those operations that modify the contents of a segment.

n. A hierarchical collection of segments related by segments referencing other segments. Given any particular segment, that segment and all of the segments directly referenced by it and its descendants constitute the segment network defined by the segment. This is sometimes also referred to as a segment tree or hierarchy.

n. The referencing of a segment by a call_segment, cond_call_segment, execute_segment, or cond_execute_segment element. This is also referred to as a call to a segment.

n. A particular set of Starbase attributes. The Starbase state can be saved at one point in time, changes can be made, and then the Starbase state can be restored to what it was at the time it was saved.

n. The act of scanning a segment network. This act of stepping through the segment network can be for displaying or refreshing the segment, or picking from it.

The control of segment and element traversal, including segment control, element control, pruning, culling, filtering, and the limiting of traversal depth.

n. The depth of nesting into a hierarchical segment network during traversal of it. While traversing the top-most segment of a segment network, the traversal depth is zero. Once traversal encounters a reference to another segment and begins traversal of that segment, the traversal depth is incremented. When traversal of the child segment is complete and traversal continues within the parent segment, the traversal depth is decremented. The Starbase Display List allows traversal depth to be restricted. The maximum traversal depth, 42 by default, can be set with the function set_traversal_depth.

n. A name set specified in the "exclude" parameter of the set_pick_filter function. Sections of the display list to be excluded from pickability filtering are identified in this set.

n. The filter that controls primitive pickability. The filter has two components: an unpickability include set and an unpickability exclude set, and these are compared with the current name set. This filter is defined by the set_pick_filter routine, and interrogated by the inq_pick_filter_sizes and inq_pick_filter routines.

n. A name set specified in the include parameter of the set_pick_filter call. Sections of the display list to be made unpickable must be identified in this set.