Data transformation and clipping in a graphics display system

• US 4,821,209 A
• Filed: 01/21/1986
• Issued: 04/11/1989
• Est. Priority Date: 01/21/1986
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Liang, Bob C., Hempel, Bruce C.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Lacasse, Randy W.
• Application Number:
  US06/821,363
• Time in Patent Office: 1,176 Days
• Field of Search: 364/518, 364/521, 364/522, 364/523, 364/300, 340/723, 340/721, 340/724, 340/727, 340/726, 340/734, 340/747, 340/750, 434/43
• US Class Current: 345/625
• CPC Class Codes: G06T 15/30 Clipping

Abstract

A display processor in a raster graphics display system includes a transformation, clipping and mapping feature which controls the transformation, clipping and mapping of graphics data. A control byte contains 5 bits identified as: M--Window to viewport mapping; P--perspective projection; D--2D/3D mode; T--transformation; and C--clipping. Each bit in the control byte is tested to determine what operations are to be performed on the figure to be drawn.

Claims

1. A display processor for selectively providing transformation, clipping and mapping processes in a graphics display system comprising, in combination;

a plurality of registers for storing branch addresses relating to said transformation, clipping and mapping processes;

one of said registers being associated with each of said processes,

means for branching to the value of one of said registers in accordance with the process being performed;

means for determining the dimensions of a figure to be displayed;

means for determining whether said figure is to be transformed;

means for providing transformation of said figure;

means for determining whether said figure is to be clipped against a predetermined clipping enclosure;

means responsive to said last named determining means for clipping said figure against said predetermined clipping enclosure; and

means for drawing said figure as a series of vectors for display on a display device in said graphic display system whereby the control decision for selective transformation, clipping and mapping processes is performed only when the transformation, clipping and mapping parameters are modified.

2. Apparatus according to claim 1, further comprising:

means for determining whether said figure is to be displayed as a perspective view.

3. Apparatus according to claim 1, further comprising:

means for determining whether said figure is to be mapped to a view port; and

means for mapping said figure to said view port.

4. Apparatus according to claim 1 wherein each of said plurality of determining means comprises input data responsive means.

5. Apparatus according to claim 1 wherein said means for transforming, clipping and drawing said figure comprise microcode control means.

6. In a graphics display system, a method for selectively controlling tranformation, clipping, mapping and drawing of a figure comprising the steps of:

determining the dimensions of a figure to be displayed;

determining whether said figure is to be transformed;

determining whether said figure is to be clipped against a predetermined clipping enclosure;

determining whether said figure is to be mapped;

said determining steps being performed whenever the associated operations are specified;

in an attributed register; and

selectively transforming, clipping, mapping and drawing vector coordinates of said figure to be mapped without any other than with only the original specified condition of the said determining steps whenever a command to draw vector coordinates of said figure is executed.

7. A method according to claim 6, further comprising the step of:

determining whether said figure is to be displayed as a perspective view.