Browse Prior Art Database

Hardware Manipulation of Three Dimensional Graphics

IP.com Disclosure Number: IPCOM000077007D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 28K

Publishing Venue

IBM

Related People

Shepherd, BJ: AUTHOR

Abstract

This is a method for displaying a three-dimensional object in perspective on a display monitor. A microcoded display control unit interprets orders from a host computer, and drives character and vector generators to produce an image on a scan-converter tube. As each image is completed, it is scanned onto a magnetic disk buffer which continuously refreshes the display monitors.

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Hardware Manipulation of Three Dimensional Graphics

This is a method for displaying a three-dimensional object in perspective on a display monitor. A microcoded display control unit interprets orders from a host computer, and drives character and vector generators to produce an image on a scan-converter tube. As each image is completed, it is scanned onto a magnetic disk buffer which continuously refreshes the display monitors.

The host computer transmits object descriptions defining three-dimensional objects in a fixed format to the control unit, which places them in a core storage buffer. The host computer then sends the graphical order with various parameters (discussed below) to obtain a copy of the object at the display monitor, or to rotate, translate or move the object, and/or plot it with perspective. One image at the display monitor may comprise multiple copies of a single object, copies of several different objects, and any combination copies, rotated or translated copies, and copies in perspective according to various display parameters.

The data representation scheme for transmission of object descriptions from the host computer, for storage in the storage buffer of the control unit is as follows: Null Line Code delta X' delta Y' Null No-op 3 Z,. Here, the line in the object space is from the preceding (old) endpoint to the endpoint with coordinates (X' old + delta X', Y' old + delta Y', Z'). In this "natural" data representation scheme, the data can be executed by the control unit for display on the monitor without transformation. In this scheme, the X and Y data are preceded by an order which describes the type of operation to be performed, the z-axis data is preceded by an order which causes the control unit to ignore the data when actually plotting an image, and the control unit will automatically produce a nonperspective view of an object defined in three-dimensional space (since all z-axis data is ignored).

In the display support system described here, an object list, which defines the object to be plotted as described above, and an instance list, which describes the location and orientation of each object to appear in the image, will be provided to the control unit by the host computer. However, unlike prior art display support systems, no plotting list is required from the host computer as the display control unit modifies and then plots a copy of the object description. Also, because of the natural data representation, the object description can be directly interpreted by the display hardware as vector commands in terms of the screen coordinates after transformation by the control unit.

To simplify the control unit microprogram, rotations may be limited to those about the display space coordinate axes, and translations to those parallel to those axes. Thus, all rotations are simple planar rotations, and translations are implemented in the control unit by adding to or subtracting from the appropriate component...