GLUNEXTCONTOUR(3G) UNIX Programmer's Manual GLUNEXTCONTOUR(3G)
gluNextContour - mark the beginning of another contour
void gluNextContour( GLUtesselator* tess,
GLenum type )
tess Specifies the tessellation object (created with
gluNewTess).
type Specifies the type of the contour being defined. Valid
values are GLU_EXTERIOR, GLU_INTERIOR, GLU_UNKNOWN,
GLU_CCW, and GLU_CW.
gluNextContour is used in describing polygons with multiple
contours. After the first contour has been described through
a series of gluTessVertex calls, a gluNextContour call indi-
cates that the previous contour is complete and that the
next contour is about to begin. Another series of
gluTessVertex calls is then used to describe the new con-
tour. This process can be repeated until all contours have
been described.
type defines what type of contour follows. The legal contour
types are as follows:
GLU_EXTERIOR An exterior contour defines an exterior
boundary of the polygon.
GLU_INTERIOR An interior contour defines an interior
boundary of the polygon (such as a hole).
GLU_UNKNOWN An unknown contour is analyzed by the
library to determine if it is interior or
exterior.
GLU_CCW,
GLU_CW The first GLU_CCW or GLU_CW contour
defined is considered to be exterior. All
other contours are considered to be exte-
rior if they are oriented in the same
direction (clockwise or counterclockwise)
as the first contour, and interior if they
are not.
If one contour is of type GLU_CCW or GLU_CW, then all con-
tours must be of the same type (if they are not, then all
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GLUNEXTCONTOUR(3G) UNIX Programmer's Manual GLUNEXTCONTOUR(3G)
GLU_CCW and GLU_CW contours will be changed to GLU_UNKNOWN).
Note that there is no real difference between the GLU_CCW
and GLU_CW contour types.
Before the first contour is described, gluNextContour can be
called to define the type of the first contour. If
gluNextContour is not called before the first contour, then
the first contour is marked GLU_EXTERIOR.
This command is obsolete and is provided for backward compa-
tibility only. Calls to gluNextContour are mapped to
gluTessEndContour followed by gluTessBeginContour.
A quadrilateral with a triangular hole in it can be
described as follows:
gluBeginPolygon(tobj);
gluTessVertex(tobj, v1, v1);
gluTessVertex(tobj, v2, v2);
gluTessVertex(tobj, v3, v3);
gluTessVertex(tobj, v4, v4); gluNextContour(tobj,
GLU_INTERIOR);
gluTessVertex(tobj, v5, v5);
gluTessVertex(tobj, v6, v6);
gluTessVertex(tobj, v7, v7); gluEndPolygon(tobj);
gluBeginPolygon(3G), gluNewTess(3G), gluTessCallback(3G),
gluTessVertex(3G), gluTessBeginContour(3G)
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