GeGbl.h

Determine is surface right-handed or left-handed. 

The handedness of a surface describes the direction of the surface normals with respect to the and parameter directions. If a surface is right-handed, then the surface normal is in the direction of the cross product of the partial derivatives with respect to and, in that order. If a surface is left-handed, the surface direction would be in the opposite direction. In other words, if a surface is right-handed, the direction of the surface normal at any given point on the surface follows the right-hand rule with respect to the and parameter directions at that point. If a surface is left-handed, the direction of its normals follow the left-hand rule 

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