Graphics display system with arbitrary overlapping viewports

• US 4,812,834 A
• Filed: 08/01/1985
• Issued: 03/14/1989
• Est. Priority Date: 08/01/1985
• Status: Expired due to Fees

• Current Assignee: Cadtrak Corporation
• Original Assignee: Cadtrak Corporation
• Inventors: Wells, Charles H.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Brier, Jeffery A.
• Application Number:
  US06/761,753
• Time in Patent Office: 1,321 Days
• Field of Search: 340/721, 340/716, 340/723, 340/724, 340/798, 340/799, 340/747, 340/750, 340/734
• US Class Current: 715/790
• CPC Class Codes: G09G 5/14 Display of multiple viewports

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. If the continuation field indicates the presence in the sequence of a continuation control word, the system acquires graphics data specified by the continuation control word and utilizes the same in the displayable image thereby producing a display with overlapping viewports.

Claims

1. A control system for generating a video displayable graphics image in which pixel data representing said image is stored in a memory and is assembled in accordance with a control table also stored in said memory, the improvement wherein:

said control table utilizes a set of control word sequences, each sequence including a first control word or words specifying the portion of said stored pixel data which is to be displayed in a segment of a single viewport and at least one continuation control word specifying the portion of said stored pixel data which is to be displayed in a segment of a separate viewport which overlaps a portion of said single viewport, and wherein;

said system includes means for utilizing the contents of said first control word or words and the contents of said at least one continuation control word to assemble a graphics image having overlapping viewports in which said segments of said single viewport and said separate viewport have no interviewport spacing between them.

2. A control system for generating a video displayable graphics image in which pixel data representing said image is stored in a memory and is assembled in accordance with a stored control table, comprising:

first means for utilizing in said control table a set of control word sequences, at least one of said sequences including a first control word or words specifying the portion of said stored pixel data which is to be displayed in a segment of a single viewport and at least one continuation control word defining the graphic contents of a segment of a separate but overlapping viewport, said first control word or words including a continuation field the contents of which indicates the presence in the corresponding sequence of said at least one continuation control word, and

second means, responsive to the contents of said continuation field, for reading out pixel data and constructing said graphics image for said overlapping viewport based on the contents of said at least one continuation control word.

3. A control system for generating a graphics image displayable on a video display, and in which said displayable image is stored in the form of pixel data in a memory and is assembled by acquiring pixel data from said memory for video scan line portions of said image defined by a set of sequential control word sequences contained in a first control table, the improvement wherein:

each control word sequence in said first control table includes at least one first control word defining a video scan line portion of a single viewport and including a continuation field, at least some of said control word sequences including at least one continuation control word defining a video scan line portion of another overlapping independent viewport,

said system including;

first means responsive to said at least one first control word for acquiring pixel data specified therein and providing the same for use in said displayable image, and

second means, actuated in response to the contents of said continuation field, for acquiring pixel data specified in said continuation control word and providing the same for use in said displayable image, wherein overlapping viewports are established.

4. A control system according to claim 3 having a second control table containing another set of sequential control word sequences defining a displayable image having a non-overlapped viewport containing image graphics data corresponding to the image graphics data of said single viewport,

said system further including:

means for alternately selecting whether said first control table or said second control table is used for generating said displayable image, wherein said displayable image will contain said single viewport by itself, or said single viewport overlapped in part by said other independent viewport, in accordance respectively with whether said second or said first control table is selected.

5. A graphics display control system for generating a graphics image displayable on a video display, comprising:

a pixel memory for storing pixel data representing said graphics image;

means for storing a control table in said pixel memory, consisting of a set of control word sequences, each sequence including a first control word subsequence containing one or more control words and specifying a segment of a single viewport, said specification including a first address identification in said pixel memory of the location of the pixel data for said single viewport segment, and information relating to the position of said segment within said displayable image,

selectable ones of said control word sequences also containing a second control word subsequence containing one or more control words and specifying a segment of another viewport intended to overlap at least a portion of said first viewport, said specification including a second address identification in said pixel memory of the location of the pixel data for said overlapping second viewport segment,

control table interpreter means, cooperating with said means for storing and responding sequentially to said set of control word sequences, for acquiring the pixel data for the segment of said single viewport specified by said first control word subsequence from said first identified address in said pixel memory and for supplying that data to generate said displayable image, and

means, responsive to the presence of said first control word subsequence, for acquiring the pixel data for the segment of said overlapping second viewport specified by said second control word subsequence from said second identified address in said pixel memory and supplying that data to generate said displayable image, wherein a displayable graphics image containing overlapping viewports is produced.