A graphic display device for shading the region between one straight line L.sub.1 connecting two points P.sub.1 and P.sub.2 and another straight line L.sub.2 parallel to the Y axis or the X axis, including a straight line coordinates generator to define a line L.sub.1 which connects the two points P.sub.1 and P.sub.2, an X or Y coordinates generator to count X or Y coordinates from a point T.sub.t on the line L.sub.1 given by the straight line coordinates generator in a predetermined direction, a controller for signalling the straight line coordinates generator when the X or Y coordinates generator completes generation of the coordinates for a selected shading line, a detector for detecting the intersections of the lines L.sub.1 and L.sub.2 in accordance with the number of the lattice points designated to provide shading on a selected shading line, a changer for changing the counting direction of the X or Y coordinates generator after detecting the intersection of the lines L.sub.1 and L.sub.2, and a shading display device to shade a region between the lines L.sub.1 and L.sub.2 in accordance with the coordinates of the lattice points designated to provide shading as designated by the straight line coordinates generator and the X or Y coordinates generator for the shading lines. The graphic display device sequentially generates shading lines parallel to either the X-axis or the Y-axis lightening the designated lattice points of a CRT or an X-Y plotter until all of the area between the two lines is shaded, thus simplifying the circuit architecture of the device.
An apparatus for generating computed images on an electronically controlled display surface is provided with an improved intensity shading generator. The shading generator operates by assigning each scan line of a raster display a fixed intensity between first and second points. The sweep position is monitored and each succeeding scan line between an initial position and a break point position of the image is monitored. The sweep intensity is incremented for each sweep line until the break point is reached, at which time new values for intensity are generated. The shading generator of this invention greatly reduces the bandwidth required to generate accurately placed intensity gradients perpendicular to the horizon in a displayed image system.
A method and apparatus for writing a vector of data into a random access memory at high speed wherein the random access memory (RAM) is partitioned into blocks of addressable storage sites and wherein storage sites within each block are individually accessible. A vector generator provides addressing and storage site enabling signals to the RAM. Boundary detectors monitor the addressing and storage site selection signals to determine whenever storage sites within a new block of storage sites are sought to be addressed. When a boundary transition is detected, a control signal is provided to the vector generator which slows the operation of the vector generator for a period of time sufficient to permit the RAM to accept a new address. For all other addresses, the vector generator is permitted to operate at a higher speed wherein access to the RAM is made by way of enabling specific storage sites within the block of storage sites being written into. The invention further providing a method and apparatus for generating surface-fill vectors, wherein a vector generator which implements the Bresenhem Algorithm is employed to generate instructions for locating points corresponding to line segments that bound the surface to be filled. The instructions are evaluated such that the X address for a given point is recorded whenever an instruction is issued which indicates a Y address change. The recorded X address are correlated to the Y coordinates over which the surface extends. The correlated X and Y addresses then define end points of surface fill vectors which can fill in the surface.
A circuit for determining the X values of each end of a series of horizontal scan lines connecting a pair of line segments each of which is defined by a pair of vertices, the horizontal scan lines defining an area to be rendered on a computer output device, comprising first and second circuit portions, each of said circuit portions including apparatus to determine the slope of a line segment, apparatus depending on the slope for determining the beginning and ending X values for each line segment for each scan line in the area to be rendered, apparatus for causing the two circuit portions to begin operation at the same scan line, and apparatus for changing the Y value for each circuit portion to the Y value of the next adjacent scan line at the same time.
A simple hardware module for insertion between a source of video signals such as a graphics computer or a VCR, and a video display device such as a TV monitor, for applying a shading effect to two-dimensional graphics for the purpose of simulating a depth of field around the resulting video image.
The display controller has a drawing processor for forming an address signal and a data signal to be supplied to a refreshing memory by processing a drawing command supplied thereto, and a digital comparator for comparing an address signal outputted from the drawing processor with an address signal set beforehand. An output of the digital comparator is utilized for referring to the drawing command to be processed. Thus the drawing command which produces a particular one of a plurality of graphic patterns forming a display on a display device can be extracted easily.
