gluTessBeginContour
Marks the beginning of a new contour within the current polygon being defined for tessellation in the GLU tessellator.
This method is used after starting a polygon with gluTessBeginPolygon and before specifying the vertices of the contour using gluTessVertex. Multiple contours can be defined within a single polygon definition. Each contour adds a loop to the polygon, contributing to its shape.
It is required to call this method before starting any vertex definitions for the contour and should be followed by a call to gluTessEndContour to complete the contour specification.