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Method for Representing Threads by Polygons in Graphics System

IP.com Disclosure Number: IPCOM000041474D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Bahri, K: AUTHOR [+3]

Abstract

In a graphics system a thread is represented by two approximated cylinders that represent the outermost and innermost diameters of the thread. A cylinder is approximated by a polygon that is defined by two circles and a set of lines that interconnect corresponding points on the circles. For an external thread (e.g., a screw), the outermost polygon is inscribed inside the circle of the outermost diameter of the thread so that the polygon does no exceed the largest diameter of the actual thread. The innermost diameter of an external thread is approximated by a polygon that is circumscribed by the circle of the innermost diameter of the thread. In some graphics systems, a hole and a solid object are both graphics objects.

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Method for Representing Threads by Polygons in Graphics System

In a graphics system a thread is represented by two approximated cylinders that represent the outermost and innermost diameters of the thread. A cylinder is approximated by a polygon that is defined by two circles and a set of lines that interconnect corresponding points on the circles. For an external thread (e.g., a screw), the outermost polygon is inscribed inside the circle of the outermost diameter of the thread so that the polygon does no exceed the largest diameter of the actual thread. The innermost diameter of an external thread is approximated by a polygon that is circumscribed by the circle of the innermost diameter of the thread. In some graphics systems, a hole and a solid object are both graphics objects. For testing for interference of parts when a solid part is to fit into a hole, the hole and the solid object are both considered to be objects that occupy the same space (with allowance for tolerances), and the distinction between the hole and the solid object is maintained by assigning to the solid object a polarity and magnitude of +1 and assigning to the hole a polarity and magnitude of -1. In this system, an external thread is assigned a polarity and magnitude of +1/2 and an internal thread is assigned a polarity and magnitude of -1/2. Like threads interfere, and threads of either polarity interfere with solid objects.

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