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gluNextContour - mark the beginning of another contour
void
gluNextContour( GLUtesselator* tess,
GLenum type )
eqn not supported
- 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 indicates 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 contour.
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 exterior 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 contours
must be of the same type (if they are not, then all 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This command is obsolete and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 compatibility 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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