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

NAME

6       gluTessNormal - specify a normal for a polygon
7

C SPECIFICATION

9       void gluTessNormal(GLUtesselator* tess, GLdouble valueX,
10                          GLdouble valueY, GLdouble valueZ);
11

PARAMETERS

13       tess
14           Specifies the tessellation object (created with gluNewTess()).
15
16       valueX
17           Specifies the first component of the normal.
18
19       valueY
20           Specifies the second component of the normal.
21
22       valueZ
23           Specifies the third component of the normal.
24

DESCRIPTION

26       gluTessNormal describes a normal for a polygon that the program is
27       defining. All input data will be projected onto a plane perpendicular
28       to one of the three coordinate axes before tessellation and all output
29       triangles will be oriented CCW with respect to the normal (CW
30       orientation can be obtained by reversing the sign of the supplied
31       normal). For example, if you know that all polygons lie in the x-y
32       plane, call gluTessNormal(tess, 0.0, 0.0, 1.0) before rendering any
33       polygons.
34
35       If the supplied normal is (0.0, 0.0, 0.0) (the initial value), the
36       normal is determined as follows. The direction of the normal, up to its
37       sign, is found by fitting a plane to the vertices, without regard to
38       how the vertices are connected. It is expected that the input data lies
39       approximately in the plane; otherwise, projection perpendicular to one
40       of the three coordinate axes may substantially change the geometry. The
41       sign of the normal is chosen so that the sum of the signed areas of all
42       input contours is nonnegative (where a CCW contour has positive area).
43
44       The supplied normal persists until it is changed by another call to
45       gluTessNormal.
46

SEE ALSO

48       gluTessBeginPolygon(), gluTessEndPolygon()
49

51       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
52       under the SGI Free Software B License. For details, see
53       http://oss.sgi.com/projects/FreeB/.
54

AUTHORS

56       opengl.org
57
58
59
60opengl.org                        07/13/2018                 GLUTESSNORMAL(3G)
Impressum