Bidirectional Normal Vector

Hi, can anybody tell me how to set the bidirectional normal vector for vertices please?

Thanks in advance!

glBidirectionalvector3f

Why I didn’t find the command glBidirectionalvector3f??? And there is no introduction to this in the red book either

http://oss.sgi.com/projects/ogl-sample/registry/EXT/coordinate_frame.txt

This extension seems not to be implemented. So you have to do it yourself.