Graphics Now

Graphics Glossary

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absolute input device
A device which reports its position relative to a fixed point.
affine transform
A transformation which preserves parallelism of lines.
ambient light
Light from a diffuse, non-directional source.
ambient-reflection coefficient
A material property, the ratio of reflected light intensity to ambient light.
antialiasing
The smoothing of an image, adjusting pixel positions or setting pixel intensities so that there is a more gradual transition between adjacent pixels.
arc
A section of a circle.
area sampling
The adjustment of pixel intensity based on intersection of graphic elements with a filter function.
B-spline
Splines consisting of curve segments whose polynomial coefficients depend on a few control points.
Bezier curve
A cubic polynomial curve defined by the end points and two control points which indirectly determine the tangent vectors at the end points.
bilevel
A display which shows images in only 2 colors.
box filter
A weighting function which is a unit cube.
brightness
The perceived intensity of light source.
canvas
An area of memory which is used as a buffer between graphics software and graphics hardware.
Cartesian coordinates
A coordinate system base on two perpendicular axes, with positive coordinates to the right of the origin and above the origin.
center of projection
A point at which projectors converge.
clipping
The restriction of graphics display to a designated area.
closure
The property of a set and an operation that the result of the operation on any member(s) of the set is a member of the set.
colorimetry
The measurement of color.
cone filter
A weighting function which has the shape of a cone, with a round base and straight sides.
diffuse reflection
Non-directional reflection of a directional light source from a material surface.
diffuse-reflection coefficient
A material property, the ratio of diffuse reflected light intensity to directional light.
dynamic range
The ratio between maximum and minimum intensities.
excitation purity
The physical purity of a color.
exclusive or mode
A graphic write mode in which each pixel bit becomes 1 only if the current display bit and the bit being written are different.
filter function
A function which is used to adjust the intensity of a pixel based on its distance from a geometric element.
font
A set of character glyphs, usually consistent in size, face, and style.
gamma correction
Correction for nonlinearities of luminance to brightness.
halftone
A printing technique which uses dot size to control lightness.
Hermite curve
A cubic polynomial curve defined by the end points and the tangent vectors at the end points.
hue
The perceived dominant color.
illumination model
A schema relating lightness to illumination.
ink jet printer
An output device which sprays drops of ink onto paper in a controlled pattern.
lightness
The perceived intensity of a light reflecting surface.
line
A one dimensional geometric figure defined by two points.
line clipping algorithm
An algorithm for determining which segment(s) of a line, if any, are within a clipping area.
luminance
The physical intensity of light.
matrix
A rectangular array of numbers.
midpoint algorithm
A rendering algorith which chooses the closest pixel.
monochromatic light
Light consisting of a single wavelength.
mouse
A small hand-held device whose relative motion over a surface can be measured.
nonuniform B-spline
A B-Spline with unevenly spaced knots.
OR mode
A graphic write mode in which each pixel bit becomes 1 if the current display bit is 1 or if the bit being written is 1.
parallel projection
A projection based on parallel projectors.
pixel
The smallest element of a digital image.
planar projection
A projection onto a plane.
point
A geometric figure with location only.
polygon mesh
A collection of connected, polygonally bounded planar surfaces.
projection
Transformation of 3D objects to a 2D representation.
prospective projection
A projection based on projectors which converge at a point.
refresh rate
(CRT) The rate at which an image is redrawn.
relative input device
A device which reports only changes in position.
replace mode
A graphic write mode which is not affected by the previous contents of the display.
rigid-body transform
A transform which does not distort an object.
rotation
A transformation which linearly changes the angle between the vector to a point and one of the axes, without changing the distance of the point from the origin.
saturation
The perceived purity of a color.
scaling
A transformation in which each coordinate is multipled by a factor.
scan conversion
The translation of graphic elements to pixel representation.
screen coordinates
A coordinate system based on the pixels of the PC BIOS, with the origin being at the upper left of the screen, and pixel rows being numbered downward.
shade
Artists' term for a color produced by mixing black with a colored pigment.
shear transform
A transformation in which the change in one coordinate is linearly related to another coordinate.
specular reflection
Directional reflection of a directional light source from a material surface.
specular-reflection coefficient
A material property, the ratio of directional reflected light intensity to directional light.
specular-reflection exponent
A material property, the power of the cos function in the Phuong equation.
tint
Artists' term for a color produced by mixing white with a colored pigment.
tone
Artists' term for a color produced by mixing black and white with a colored pigment.
translation
Uniform translation of points to a new location without change in the size or orientation of an object.
uniform B-spline
A B-Spline with evenly spaced knots.
vanishing point
A point at which the projections of parallel lines meet.
vector
An ordered n-tuple of real numbers.
weighted area sampling
The adjustment of pixel intensity based on intersection of graphic elements with a filter function.
weighting function
A function which is used to adjust the intensity of a pixel based on its distance from a geometric element.