Graphics clipping circuit
AssigneeSmiths Industries Limited
InventorStephen P. Taylor
Life of this patent
Estimating the term…
Abstract
A circuit is provided which accepts digital position information from a graphics generator. This information serves as an input to a look-up table to determine whether the position information would cause any portion of a symbol from the graphics generator to be inside a clipping boundary, which boundary frames higher priority symbology. If this is found to be the case, the circuit excludes or clips the symbol portion that would otherwise interfere with the higher priority symbology.
Claims5
In a system for clipping graphic symbols on a CRT, within preselected linear or curvilinear clipping boundaries, a logic circuit for controlling CRT intensity, the logic circuit comprising:
- input terminals at which first and second coordinate positional data regarding graphic symbols are presented;
- memory means for storing a look-up table enabling correlation between first coordinates of points for corresponding second coordinate addresses, of preselected linear and curvilinear clipping boundaries;
- comparator means connected at its input to the input terminals and the memory means for comparing an instantaneous first positional coordinate of the symbol at the input terminals with the coordinates in memory;
- and
- gating means, connected at its input to the output of the comparator means, for generating a
- (a) first intensity signal at the output thereof when a symbol point, at a moment of time, is located within a clipping boundary and
- (b) second intensity signal at the output thereof when a symbol point is located outside a clipping boundary.
In a system for clipping graphic symbols on a CRT, within preselected linear or curvilinear clipping boundaries, a logic circuit for controlling CRT intensity, the logic circuit comprising:
- input terminals at which first and second coordinate positional data regarding graphic symbols are presented;
- memory means for storing a look-up table enabling correlation between first coordinates of points for corresponding second coordinate addresses, of preselected clipping boundaries;
- storage buffer means connected in circuit between the first coordinate position input terminal and the memory means;
- means connecting the output terminals of a graphics generator to the input terminals for writing first coordinate positional data into the memory from the buffer means as the memory is addressed by second coordinate positional data thereby establishing the clipping boundary look-up table during initialization of the system;
- comparator means connected at its input to the input terminals and the memory means for comparing an instantaneous first positional coordinate of the symbol at the input terminals with the coordinates in memory;
- gating means, connected at its input to the output of the comparator means, for generating a
- (a) first intensity signal at the output thereof when a symbol point, at a moment of time, is located within a clipping boundary and
- (b) second intensity signal at the output thereof when a symbol point is located outside a clipping boundary.
Dependencies are inferred from the claim text.