1GLUPICKMATRIX(3G)                OpenGL Manual               GLUPICKMATRIX(3G)
2
3
4

NAME

6       gluPickMatrix - define a picking region
7

C SPECIFICATION

9       void gluPickMatrix(GLdouble x, GLdouble y, GLdouble delX,
10                          GLdouble delY, GLint * viewport);
11

PARAMETERS

13       x, y
14           Specify the center of a picking region in window coordinates.
15
16       delX, delY
17           Specify the width and height, respectively, of the picking region
18           in window coordinates.
19
20       viewport
21           Specifies the current viewport (as from a glGetIntegerv() call).
22

DESCRIPTION

24       gluPickMatrix creates a projection matrix that can be used to restrict
25       drawing to a small region of the viewport. This is typically useful to
26       determine what objects are being drawn near the cursor. Use
27       gluPickMatrix to restrict drawing to a small region around the cursor.
28       Then, enter selection mode (with glRenderMode()) and rerender the
29       scene. All primitives that would have been drawn near the cursor are
30       identified and stored in the selection buffer.
31
32       The matrix created by gluPickMatrix is multiplied by the current matrix
33       just as if glMultMatrix() is called with the generated matrix. To
34       effectively use the generated pick matrix for picking, first call
35       glLoadIdentity() to load an identity matrix onto the perspective matrix
36       stack. Then call gluPickMatrix, and, finally, call a command (such as
37       gluPerspective()) to multiply the perspective matrix by the pick
38       matrix.
39
40       When using gluPickMatrix to pick NURBS, be careful to turn off the
41       NURBS property GLU_AUTO_LOAD_MATRIX. If GLU_AUTO_LOAD_MATRIX is not
42       turned off, then any NURBS surface rendered is subdivided differently
43       with the pick matrix than the way it was subdivided without the pick
44       matrix.
45

EXAMPLE

47       When rendering a scene as follows:
48
49           glMatrixMode(GL_PROJECTION);
50           glLoadIdentity();
51           gluPerspective(...);
52           glMatrixMode(GL_MODELVIEW);
53           /* Draw the scene */
54
55
56       a portion of the viewport can be selected as a pick region like this:
57
58           glMatrixMode(GL_PROJECTION);
59           glLoadIdentity();
60           gluPickMatrix(x, y, width, height, viewport);
61           gluPerspective(...);
62           glMatrixMode(GL_MODELVIEW);
63           /* Draw the scene */
64
65
66

SEE ALSO

68       gluPerspective(), glGet(), glLoadIdentity(), glMultMatrix(),
69       glRenderMode()
70

72       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
73       under the SGI Free Software B License. For details, see
74       http://oss.sgi.com/projects/FreeB/.
75

AUTHORS

77       opengl.org
78
79
80
81opengl.org                        07/13/2018                 GLUPICKMATRIX(3G)
Impressum