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# Geometric Link Picking System using Cursor Transformation

IP.com Disclosure Number: IPCOM000114713D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 71K

IBM

## Related People

Murohashi, S: AUTHOR [+3]

## Abstract

Disclosed is an algorithm for two-dimensional/three-dimensional picking. It is designed to select two-dimensional/three-dimensional vertices array, crossing or with in a parallelogram pick window, displayed on two-dimensional display device. Picking is done without perspective projecting, that is project vertices from data coordinates to display coordinates, which lessen the calculation amount. Also, by using Dynamic Quick Rejection algorithm, the entire calculation amount will be lessen.

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Geometric Link Picking System using Cursor Transformation

Disclosed is an algorithm for two-dimensional/three-dimensional
picking.  It is designed to select two-dimensional/three-dimensional
vertices array, crossing or with in a parallelogram pick window,
displayed on two-dimensional display device.  Picking is done without
perspective projecting, that is project vertices from data
coordinates to display coordinates, which lessen the calculation
amount.  Also, by using Dynamic Quick Rejection algorithm, the entire
calculation amount will be lessen.

The disclosed algorithm offers some improvements in the
performance of picking graphic objects.

Fig. 1 shows an example of picking vertices displayed on
two-dimensional display device.

The picking procedure consists of the following three steps:
1.  Check if vertices are two-dimensional vertices, or
three-dimensional vertices.  If three dimensional vertices,
then
goto step 3, else goto step 2.
2.  Generate inverse transformation of pick window (IPW).  This
will
be done by generating inverse matrix of perspective projection
matrix.  IPW will be parallelogram if there is inverse matrix,
else IPW will be a zone, entire space, or null space (Fig. 2).
If
IPW was null space, no vertices will be picked.  If IPW was
entire
space, all the vertices will be picked, else use Dynamic Quick
Rejection algor...