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display_filter(6/16/92) display_filter(6/16/92)

NAME

display_filter - abstract class for visualization pipeline filters.

DESCRIPTION

Display_filter is an abstract class that provides methods and data structures for the various display_data pipeline filters. Display_filter takes as input a display_data and generates on output a display_data.

The primary purpose of display_filter is to provide methods and instance variables for controlling the masking of information. Masking is used to turn on/off parts of the display_data. The meaning of the mask depends upon the particular filter: see spcific man pages for examples.

SUPERCLASS

display_feature

INSTANCE VARIABLES

mask is a list of 0's and 1's that indicate wheather or not an item is displayed or not. If the mask length is shorter than the number items that are being displayed (polygons, vectors etc...) then the mask is repeated multiple times.

mask_size is the number of numbers in the mask

MESSAGES

mask=(0,1,0,1,1,...) sets the mask to the argument list. Non-zero values turn the data item on, zero values turn it off.

mask+(0,1,0,...) turn on/off additional values.

mask? returns the value of the mask on the argument stack

mask_size? returns the number of values in the mask

EXAMPLE

See examples of warp_scalar, warp_vector, hash, and contour_filter.