Additive/3D Printing

The Language of Computer Graphics

Nov. 15, 2002

Here are some of the most widely used terms associated with high-end graphic capabilities: Aliasing - The jagged lines that result from drawing on a raster screen.

Here are some of the most widely used terms associated with high-end graphic capabilities:

Aliasing - The jagged lines that result from drawing on a raster screen. Most noticeable in low-res displays.
Antialiasing - A technique that reduces the jaggedness of lines on raster screens. Usually involves displaying pixels between the line and the background at different intensities, thereby blurring the line slightly and diffusing the effect.
Attributes - Qualities given to a particular primitive or segment. For example, the attributes of a point are its color and location, while the attributes of a line are its color, length, location, and orientation.
Bit blt - Also known as a bit-block transfer. This is a raster operation that moves a block of bits from one part of the frame buffer to another. This is a quick way of moving a portion of an image around on the display screen.
Bit plane - An array of memory wherein one bit corresponds to each pixel in the display. Frame buffers are generally referred to as containing one or more bit planes. For example, an 8-bit system has 8-bit planes.
Declutter - Elimination of unwanted details in a display through select deletion of segments. Segment can be automatically added back to the display if the user zooms in on any particular area.
Display list - A list of vectors, curves, pixel states, and text that defines the graphics data to be displayed. Moving this information to the terminal speeds response time.
Double buffering - Display memory, generally known as frame buffers, is divided in two. One buffer stores the current display information, while the other creates the next view. The use of double buffering provides continuity and realism in animated sequences because it allows fast switching between views.
Frame buffer - Memory that stores a full frame of picture data. There can be more than one bit of frame buffer memory assigned to each pixel. The more bits assigned to each pixel, the more complex the image that can be displayed.
Pixel - An abbreviation for picture element. It is the smallest portion of a display that can be addressed and given a color or intensity.
Primitives - Basic elements of a graphics display such as points, lines, curves, polygons, and alphanumeric characters.
Projection algorithm - A rule determining the angle at which visual structures are projected on a view plane.
Raster - Basically, a grid of pixels that make up an image. Operations done on frame buffers are called raster ops. Raster scan data is what is used to control the intensity of the electron beam in the CRT monitor.
Real-world coordinates - Measurements expressed in the engineering units of the application.
Vector mode - A vector, or stroke, mode of display used to generate line segments from pairs of specified endpoints. Vector mode is usually implemented on raster systems through software that illuminates specified pixels lying along a prescribed line segment.
View plane - The plane on which images are projected. This plane can be parallel to the display screen or tilted.
View volume - The portion of a 3D model displayed at any point in time.
Z-buffer - In 3D graphics, memory locations corresponding to pixels on the screen. But the Z buffer contains data relating only to the depth axis of the image. Z buffering is primarily used in hidden surface removal algorithms.