- application
- A computer program. A CAD application can carryout extremely
complex tasks specific
- to a particular drawing problem. CAD
applications run in tandem with the CAD software to
- perform
specialized or automated tasks. Some examples of CAD applications
specific to theatre include programs to automate the drawing of
construction drawings and light plots.
- arrowhead
- The part of a dimension or leader which points to an object or
extension line. Arrowheads usually can be drawn automatically in
several styles or shapes.
- attribute
- Information or data about a drawing object which can be hidden or
appear in the drawing as text. Often this information can be
extracted from the drawing and used in a spreadsheet or other
program.
- Bezier curve
- A curve defined by endpoints, tangent lines, and control points at
the ends of the tangent lines. Altering the length and angle of
tangent lines alters the shape of the curve.
- Bitmap
- A pixel based graphic or image inserted in a drawing. Bitmaps can
be sized but not edited with most CAD programs.
- block
- see symbol.
- CAD
- Computer-aided design. Common CAD programs include: Generic CADD
(DOS), AutoCAD (DOS and Windows), Claris CAD (Mac), MiniCAD (Mac),
DesignCAD (DOS and Windows), Drafix CAD (Windows) and Visual CADD
(Windows). Programs differ greatly in features, complexity, cost,
and hardware requirements.
- CADD
- Computer-aided design and drafting.
- Cartesian
coordinates
- See coordinates.
- center point
- The defining point at the exact center of a circle, arc, regular
polygon or ellipse.
- chamfer
- A diagonal line which connects points on two intersecting objects
such as an angled corner.
The chamfer tool is an
edit.
- color
- A property of any drawing object which defines the color in which
it appears on the screen and the color in which it is printed. Color
is often associated with what layer an object is on and often
determines how that object will appear on a printout with regard to
line thickness and
line
type.
- constraint
- A drawing tool which limits drawing to a particular point, line or
angle. Some common constraints are
snap
to grid and ortho.
- control points
- Points determining the path and shape of a
Bezier
curve.
- coordinates
- A sytem of numbers used to locate a point or object in a drawing.
In the Cartesian coordinate system 2 numbers x and y are used to
describe the location of a point in the horizontal and vertical
dimensions respectively. 3D CAD programs add the z coordinate which
describes distance in the third dimension.
In the Polar coordinate system a point is described by a distance
and an angle where 0° exends horizontally to the right.
- cursor
- The screen symbol or icon which represents the current mouse
location relative to the drawing window or viewport. The cursor may
appear as crosshairs or another symbol based on which command is
active.
- curve
- A complex entity created by the definition of endpoints of spline
curve sections. Note: curve entities cannot be trimmed to and do not
respond to many editing commands. See also
Bezier
curve
- dimension line
- A line, usually with an arrow indicatiing the direction and
distance of a drawing dimension. See also
extension
line.
- drawing
database
- The central part of a CAD drawing. A sequential list of all
objects which exist within a drawing along with all parameters and
definition points.
- drawing units
- See units.
- drawing window
- See viewport.
- DXF
- Drawing exchange format created by Autodesk. An ascii text file
format describing drawing data and settings to translate drawings
between programs and formats. Note: DXF is not a standardized format
and different programs convert or ignore different entities found in
a DXF file.
- edit
- The process of modifying a drawing object or entity.
- edits
- A class of drawing commands used to modify drawing entities or
objects. Common edits include:
trim,
rotate,
move
and stretch.
- ellipse
- A CAD drawing primitive entity defined by a major axis, minor axis
and centerpoint. An ellipse may also be constructed out of arcs and
line segments. An ellipse created in this way is not mathematically
a true ellipse but is an easier object to edit.
- environment
- The over-all setup of a CAD program including all drawing
settings, colors, units, etc. comprise the drawing environment.
- explode
- A common command which break objects apart into their component
pieces. Explode most often works on
symbols,
breaking them back into their component pieces. In some CAD programs
other entities are explodable such as
text
lines, polylines,
or other complex objects.
- extension line
- The line which extends from a measured line or object to the
dimension
line, showing the extent of the measured distance.
- fillet
- (Rhymes with skillet). An arc connecting endpoints of two
intersecting lines or objects, often a rounded corner.
- fill
- A complex object defined by a series of points or a bordering
object such as a circle or polyline which fills the defined are with
solid color. The display of a fill is highly dependant upon the
display or printer/plotter being used. See also
hatch.
- font
- The typographic style property of
text.
Fonts may be drafting style (one line thickness) or typographic such
as that being used in this document. Font types and styles vary
widely between CAD programs and are one of the most difficult
entities to translate when trying to exchange drawing data between
different programs.
- grid
- A drawing tool which is usually a pattern of regularly spaced dots
or lines which make the alignment and drawing of objects easier. A
snap
to grid tool constrains
or locks all drawing to grid points only.
- group
- A collection of objects which can be manipulated as one object.
- handles
- See object
handles.
- hatch
- A complex object defined by a series of points or a bordering
object such as a circle or polyline which fills the defined area
with a repeating pattern of lines. Hatches have a scale property
which determines the size and density of the repeating pattern. See
also fill.
- layer
- A property of any drawing object. Usually objects are organized
onto different layers for organazational purposes and ease of
drawing, viewing and editing. Layers often can be named and have
default colors
and line
types associated with them. MiniCAD Layers have the added
ability to have associated properties of scale, view, and
projection. These added properties of MiniCAD layers enables MiniCAD
to fuction in a way similar to AutoCAD paperspace.
- leader
- A line with an arrowhead and attatched text pointing at another
object.
- leader line
- The line portion of a
leader
connecting the shoulder to an
arrowhead.
- line
- A CAD primitive entity defined by two endpoints.
- line type
- A property of any line, circle, curve, or arc. Line type describes
a repeating pattern of lines and spaces. Lines may be solid, dashed,
alternate, etc. The additional property of line type scale
determines how often in a given distance a pattern of lines and
spaces repeats.
- line width
- A property of any line, circle, curve, or arc. Line width
describes how thick a line or other object appears on the the screen
or on a printout. Different CAD programs use different schemes for
acheiving line width.
- macro
- A sequence of commands recorded and saved for easy playback. Well
designed macros can save a great deal of drawing time. See also
script
and application.
- major axis
- The longer axis of an
ellipse.
- manual entry
- The process of entering points manually by typing
coordinates
as opposed to clicking within the viewport.
- markers
- A line marker is used to mark the end points of lines.
- minor axis
- The shorter axis of an
ellipse.
- move
- A drawing editing tool which moves objects or selection sets to a
new drawing location by changing all definition points by a given
distance.
- nested
- Objects inside of other objects.
Symbols
may be nested within other symbols. Drawing commands can be nested
or executed while other drawing commands are active.
Macro
programming objects can be nested in terms of their control
structure.
- object handles
- In a windows CAD program the handles which appear when an object
is selected. Handles often allow objects to be
stretched,
rotated,
or moved.
Note: in AutoCAD handles refer to arbitrary names assigned to each
drawing entity in the drawing database so that macros and
applications may refer to specific entities directly.
- offset
- The distance between two objects. Offsets are often used to draw
parallel lines or determine the location of a dimension. In AutoCAD
a command which creates a duplicate of an object at a specified
distance.
- origin
- The point in a drawing with the x,y
coordinates
of 0,0.
- ortho
- Short for orthagonal. Usually refers to objects placed
horizontally or vertically within a drawing. Ortho mode is a
constraint
which limits all drawing to regular 90° angles. In some CAD
programs other ortho angles and modes may be set.
- pan
- The process of altering the drawing view by moving the viewpoint
laterally relative to the drawing.
- polar
coordinates
- See coordinates.
- polygon
- A complex object composed of three or more straight lines in a
closed figure. Polygons are treated differently by diffent CAD
programs. Often a polygon is simply a closed
polyline
entity.
- polyline
- A complex object composed of two or more lines, curves, or arcs
which have contiguous endpoints. A closed polyline or
polygon
has its endpoints joined into a closed form. Polylines are more
difficult to edit than a form drawn with individual line segments,
but offers some advantages when editing or building surfaces and 3
dimensional objects.
- primitive
- The simplest drawing entities from which all objects are built.
Common primitives include: point, line, circle, arc, and ellipse.
- prompt
- A program message often located on the programs status line.
- radial array
- An editing command which creates multiple copies of objects by
copying them around a centerpoint for a given angle.
- real scale
- Objects in a CAD program a drawn at full scale or 1:1. See
scale.
- redraw
- The process by which the video display is updated cleaning up any
unwanted marks or construction points. See also
regenerate.
- reference
points
- Points associated with drawing objects which allow an object to be
selected, grouped, and manipulated. Reference points are often not
visible. One example is the reference point of a text line which is
often found at the lower left hand corner of the text line. To
select a text entity it is often neccessary to click near this
invisible point or include it within a selection window.
- regenerate
- The process by which the view updated from the drawing database
cleaning up any unwanted marks or construction points. Similar but
more comprehensive and time consuming that a redraw. Note: on some
CAD packages these processes are synonymous.
- relative
coordinates
- Drawing coordinates
which when manually
entered are interpreted as relative to the last point entered.
In AutoCAD relative coordinates are entered by preceeding the
coordinate pair with the @ sign such as @2,3.
- resolution
- The clarity or degree to which individual elements can be
discerned on a monitor or print/plot. Common monitor resolutions
include 640x480 (Eiki projector) 1280x1024 (student workstations)
measured in pixels. Common laser printer and plotter resolutions
range from 300x300 to 600x600 dots per inch. Resolution of these
devices determines how accurate a printout will be or how accurate
an object will appear on the screen. The actual resolution of
objects saved in the
drawing
database is usually much higher to insure a high degree of
accuracy. When drawing objects are viewed on screen or plotted their
size and position is rounded to the nearest dot at the resolution of
a given device.
- rotate
- A drawing editing tool which rotates objects or groups of objects
based on a center of rotation and an angle.
- rubberbanding
- A feature of many CAD programs which shows how a line or other
object will look before it is actually placed. An example is with
the line command. A starting point is selected after which a line
appears rubberbanded between the first point and the
cursor.
As soon as another point is selected the actual line is drawn and
the rubberband moves to the next point.
- scale
- 1) An editing tool which changes the size of an object relative to
percentage. Some objects can be rescaled to different percentages in
the x and y directions.
2) The relative size at which a drawing is viewed on the screen or
printed/plotted. Scale is often represented as a ratio where 1:1 is
full scale, 1:12 = 1" =1'-0", 1:24=1/2"=1'-0"
etc.
- script
- A list of drawing commands which can be typed in a text editor and
then loaded and executed with one command. Different scripting
methods are supported by different CAD programs. Scripts are useful
for performing repetitive tasks such as drawing setups.
- selection set
- One or more objects selected for action with a single command.
Often items are selected this way by drawing a window around them or
holding down the shift key while selecting them individually.
- snap
- A drawing tool which locates points exactly by finding an existing
point within the drawing database which is closest to a point
selected with the on the screen. Some common snaps are: snap to
nearest point, snap to midpoint, snap to intersection of two lines,
etc.
- snap to grid
- A drawing constraint which forces all points picked to fall on the
currentl grid.
- stretch
- An editing tool which moves some of the points which define an
object and leaves others.
- trim
- A drawing editing command which causes one object to end exactly
at another. Trim points are calculated mathmatically so they are
exact. Some complex objects such as curves cannot be trimmed to.
- symbol
- A collection of drawing objects defined as a single complex
entity. Defining and using symbols speeds drawing and makes drawing
files more compact. Symbols are also called blocks (AutoCAD) or
components (Generic CADD).
- tangent
- A line which intersects a circle, ellipse or arc at only one
point. Tangent lines to
Bezier
curves define the shape of the curve.
- toggle
- A drawing control or setting which is either on or off. Subsequent
execution of the command reverses the state of the parameter. One
togle is the dispaly grid
command.
- units
- Units of measure represented by numbers in a CAD program. Usually
units are inches or feet, but can be considered to be anything from
millimeters to light years.
- vertex
- A point defining the junction of a segment within a
polyline
or polygon.
- view
- The graphical representation of the geometry stored in the drawing
database which appears in the drawing window or viewport. A view has
a center point and a scale or zoom. Multiple views of one drawing
may be open in seperate windows or viewports simultaneously.
- viewport
- The window or frame within which a view of the drawing is visible.
In some complex CAD programs viewports are considered complex
objects and can be placed in drawings. Many programs also support
the use of multiple viewports which can simultaneously show
different parts of the same drawing. This is especially important
when working in 3D.
- zoom
- The way the view is changed by magnifying or reducing the image on
the screen. Zoom scales the view only and does not affect the actual
size of drawing objects.
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