alias: A "nickname" that can stand in for a full segment name, or for a part of a segment name.
attribute: Attributes control the manner in which the various pieces of your scene will be displayed on the screen. They are the how rather than the what. Compare picture element.
camera: The virtual viewing device you position in your scene. What the camera can see is what will be shown in the relevant screen window.
camera field: The amount of your scene, in terms of object space coordinates around the "target", that will end up within your camera's field-of-view. Compare with "camera lens..
camera lens: As in "zoom" or "wide-angle" or "regular". The lens is measured in terms of the "field" that can be seen through it.
camera position: Location within your virtual scene at which your camera will stand.
camera projection: A toggle switch that lets 3-D scenes be displayed "orthographically" as is done for engineering or architectural drafting. Or "in perspective," which resembles the way the eye sees.
camera target: Location within your virtual scene at which your virtual camera will aim.
camera up vector: The "up vector" direction in your scene will become the "up" direction on your display screen.
camera volume: If the camera is orthographic an infinitely long box in your object space. If you have a perspective camera, an infinitely long pyramid based at the camera within your object space. The box or pyramid is projected onto the screen.
cursor: A special marker on screen that travels with your pen or mouse. Or a special marker within a block of text that marks a "current position" under program control.
database: The amount total of information the system has stored away about your graphics world. Includes the "segment tree," the defined colors, the debugging state, and so on.
declarative: A programming style, particularly a graphics programming style, in which you declare what your scene is, rather than describe how one might go about drawing it. Compare with "stream-of-consciousness."
dolly: A verb denoting the action of moving a camera left-right, in-out, or up and down.
drawing primitive: A single line, polyline, polygon, marker, circle, ellipse, arc, text, shell, or mesh. In general, something that might be "inserted" into a scene. Synonymous with "geometrical element" and "picture element."
edge: A line connecting two vertices in a polygon, shell, or mesh. A line defining the border of a circle or ellipse might or might not be drawn differently from the interior of the surface.
edge shinethrough: Edge shinethrough occurs when faces are pushed back so far that an edge that should be hidden appears either partially or completely. In the figure below, a hidden interior edge shines through partially at the top of a pyramid when the left front face of the pyramid should have hidden it.
You can address this issue by updating the \ref Set_Rendering_Options_face_displacement "face displacement" option in Set_Rendering_Options as well as following the HOOPS camera set up guidelines.
Edge Stitching : When both the edges and faces of a polygon are visible, they are almost exactly the same distance form the camera. Due to z-buffer precision problems, an edge can appear dashed as it pops in and out from behind one or more faces. In the figure below, three different edges in a pyramind appear as dashed lines when they should appear solid.
You can address this issue by updating the \ref Set_Rendering_Options_face_displacement "face displacement" option in Set_Rendering_Options as well as following the HOOPS camera set up guidelines.
geometry: Any collection of one or more drawing elements. The collection may or may not be coherent enough to be called a "scene."
hit-test: The action the system undertakes to determine what the user is pointing to on the screen.
image: A rectangular array of single-pixel color values: as in a photograph.
includee: A segment that sits "off to the side" and is used in more than one location in the segment tree. Usually contains an object of which multiple views are needed, or an icon.
inclusion: The act of "borrowing" a segment from its usual context so that it can be used more than once.
ink: A polyline that is laid down incrementally.
inking: The act of building an "inked" polyline.
key: An identifier to a picture element, such as a polyline. Use to retrieve the picture element from the database when you want to make adjustments to it.
line: A picture element that is a straight line segment defined by its two endpoints.
line weight: The width or boldness of a line or polyline.
marker: A small circle, square, dot, or whatever marks a point in your scene.
mesh: A collection of 3-D quadrilaterals connected as a rectangular array.
mode non-segmented: A special operating mode in which you don't have to worry about "segments". Non-segmented mode is automatically "streaming mode."
object: A piece of the picture you're building, such as one tire, several tires, or one automobile. One logical object might be contained in a single "segment," or it might be spread out between a segment and multiple sub-segments. When you put more than one object into a segment, the collection should make sense as an "object." For instance, four tires and a body equal an automobile.
object space: The infinitely large (in principle) territory in which to define graphical entities. Object space is just a big empty Cartesian space. Compare with "screen space."
orbit: The path the camera takes as it travels around the camera target at a fixed distance.
orthographic: A projection method in which "far-away" objects are collapsed together with "nearby" objects as they are laid onto your viewing screen. Compare with "perspective."
path name: A segment name that includes the "path" the system must follow to get to it, starting from the root.
perspective: A projection method in which "far-away" objects are drawn smaller on your viewing screen than "nearby" objects are. Compare with "orthographic."
picture element: An indivisibly small piece of your picture, such as a single polygon or text string. Synonymous with "drawing primitive."
pixel: The smallest resolvable dot on your display screen.
point: A location in a coordinate space (usually object space). Defined by an X, a Y, and a Z value.
polygon: A connected, closed, and co-planar sequence of straight line segments.
polyline: A connected sequence of straight line segments.
primitive: Short for "drawing primitive".
projection: What happens when the three-dimensional space your objects are in is mapped to your two-dimensional viewing screen. Either "perspective" or "orthographic."
root: The one special segment in the system that is not contained in any other segment.
scene: Not just what is visible through your "camera" lens, but rather a collection of objects assembled into a coherent whole.
screen space: The coordinate system used to measure screen windows. The lower left of the screen (or the containing window) is defined as (-1, -1); the upper right is defined as (+1, +1).
screen window: A region of the screen in which you can cause views of your scene to appear. Synonymous with "window."
segment: A place to keep graphical information. "Graphical information" might consist of picture elements, drawing attributes, and subsidiary segments.
segment tree: The root segment plus its myriad subsegments, subsubsegments, and so on. The tree is upside-down. The root is at the top of the tree. The branches become smaller and the leaves more numerous as you move down the tree.
shell: A collection of polygons, usually adjacent, form a faceted surface or a closed polyhedron.
sibling windows: Two or more screen windows (windowed segments) that lie side-by-side in the segment tree.
simple name: A segment name that does not contain wildcards.
standard segment: One of the segments automatically set up as the system begins execution.
consciousness, stream-of-: A style of programming, in which the graphics commands are executed as a list of things to do. "Select a red pen" is a stream-of-consciousness thing to do. Saying "this thing is red" is a "declarative" thing to do.
streaming mode: The "stream-of-consciousness" style, as applied to a segment.
string: In C, a character array or double-quoted string. In Pascal, a character array or quoted-string. In Fortran, a character variable, character constant, or quoted-string.
style segment: A user-defined special segment, which other segments may refer to when you want them all drawn in a standard "style"---patterned, or highlighted, or even drawn invisibly.
subsegment: A segment that is a piece of, and subordinate to, a higher-level segment.
subwindow: A screen window that is strictly subordinate to and contained in another screen window. This occurs when a segment with a screen window has subsegments that also have screen windows.
text: A picture element consisting of a sequence of characters.
text font: A font family, such as Courier or Helvetica. A style of text, such as Bold or Italic, and a font size for that text style.
text path: Defines the direction the system should step along as it lays down the characters in a text string. Usually from left-to-right, but might be something else.
transform: A mathematical operation that maps coordinates in one space, such as your object space, into coordinates in another space, such as the surface of your viewing screen.
unnamed segment: A segment created without an explicit name. This is useful if you generate segments in a loop and do not need to refer to them, or if you work primarily with segment keys rather than names.
user space: An alternate name for "object space."
vector: A direction in a three-dimensional Cartesian coordinate space.
wildcard name: A segment name that, due to using wildcard characters or commas, might refer to more than one segment at a time.
window: A region of the screen in which you can cause views of your scene to appear. Other windows can show other views or other scenes.
window frame: The decorative border around a screen window.