Abstract: In this graphics display system with arbitrary overlapping viewports, a display graphics image is assembled by acquiring from a source of image graphics data line portions of said image defined by a set of sequential control word sequences contained in a control table. Advantageously, each control word sequence includes at least one first control word defining a line portion of single viewport, and a continuation field. At least some of the control word sequences also include at least one continuation control word which defines a line portion of another independent but overlapping viewport. To produce the display, the system includes means responsive to the control words for acquiring graphics data specified therein and providing the same for use in the displayable image.

Abstract: In this graphics data handling system a CAD workstation cooperates with the host computer which stores a site list representation of a complex three dimensional structure. Backdrop viewfile representation of the structure, advantageously with hidden surfaces removed, are established in vector format by data transformation from the site list. Bit map raster views are derived from the backdrop viewfiles, and are stored in a pixel memory. Video screen images of selected views of the structure are derived by readout of the raster view data from the pixel memory.During panning of the video screen display, when the image nears the edge of a raster view, a strip of data in that raster view, in the region opposite the direction of panning travel, is deleted. This is replaced by new data from a strip of the backdrop viewfile representing the portion of the structure immediately contiguous to the existant raster view in the direction of panning travel.

Abstract: In this computer graphics display system, individual viewports of arbitary arrangement, number and content are produced on a video screen. The graphics content, display parameters and interviewport spacing all are specified by a set of control word sequences stored in a control table. Each sequence is associated with one scan line segment of an individual viewport, and consists of one or more control words that specify (a) the graphics image memory location of the pixel data to be included in that viewport segment, and (b) display parameters which specify how that pixel data is to be processed before supply to the video screen.Control word display parameters and the associated graphics image (pixel) data are alternately obtained from a control/pixel memory and supplied to a first-in-first-out (FIFO) memory. At the outbound side of the FIFO memory, a controller enters the display parameters in appropriate registers.

Abstract: This video graphics raster display system effectively facilitates panning over an image that is arbitrarily larger than the image memory from which the display is generated. To accomplish this, the image memory is addressable "toroidally", i.e., in modulo or wraparound fashion. Thus, if a memory address boundary is reached during a raster readout, the readout continues without interruption from the opposite boundary.The image memory is slightly larger than would be required to store only the image currently being displayed. The excess memory area includes a border area, surrounding the current readout area, which contains image data that forms a continuation of the image currently being read out and displayed. This allows immediate panning into the border area. Further, the excess memory area includes a "rewrite area" on the other side of the border zone from the current readout area into which new, image continuation data may be entered while panning takes place.