gleJoinStyle Documentation

Subroutine Descriptions

int gleGetJoinStyle (void); 
void gleSetJoinStyle (int style);	      /* bitwise OR of flags */ 
Query and Set the join style flags. This word is a bitwise OR of the flags described below.

Extrusion Join Styles

Draw polycylinders, polycones, extrusions, etc. with no special treatment of the extrusion ends.

Draw polycylinders, polycones, extrusions, etc. by extending the different segments until they butt into each other with an angular style.

Draw polycylinders, polycones, extrusions, etc. by joining together the different segments and slicing off the joint at half the angle between the segments. A cap is drawn. Note that the slicing plane runs through the origin of the contour coordinate system. Thus, the amount of slice can be varied by offsetting the contour with respect to the origin.

Note that when two segments meet at a shallow angle, the cut join style will potentially shave off a whole lot of the contour, leading to "surprising" results...

Joints will be rounded. Strictly speaking, the part of the joint above the origin will be rounded. The part below the origin will come together in an angular join.

Mask bits. This can be used to mask off the bit field that defines the join style.

End Caps

If this is set, a cap will be drawn at each end of the extrusion.

Automatic Normal Vector Generation

A normal vector is generated per facet. Useful for having an extrusion have a "faceted" look, such as when extruding a square -- each of the four sides of the square will look flat.

Normal vectors are generated so that they lie along edges. Useful for making angular things look rounded under lighting. For example, when extruding a hexagon and using this flag, the hexagonal extrusion will look (more like a) smooth perfectly round cylinder, rather than a six-sided shape.

Normal vectors are generated so that they both lie on edges, and so that they interpolate between neighboring segments. Useful for drawing "spaghetti" -- extrusions that follow a spline path. Because the spline path must be "tessellated" into small straight segments, each segment will look straight unless this flag is set.

A mask useful for masking out the "norm" bits.

Closed or Open Contours

If this bit is set, the contour will be treated as a "closed" contour, where the last point connects back up to the first. It is useful to set this flag when drawing closed shapes (such as extruded cylinders, star-shapes, I-Beams, etc.) When drawing open extrusions (e.g. corrugated sheet metal), you DON'T want to set this flag.

The End

Originally developed by Linas Vepstas in 1991
Version 2.0 -- port to OpenGL, 1993
Version 2.1 -- assorted touch-ups, cleanups, etc.
Version 2.1.1 -- additional demos