Description
void 
swf_lookat ( float view_x, float view_y, float view_z, float reference_x, float reference_y, float reference_z, float twist)
     The swf_lookat() function defines a viewing
     transformation by giving the viewing position (the parameters
     view_x, view_y, and
     view_z) and the coordinates of a reference
     point in the scene, the reference point is defined by the
     reference_x, reference_y
     , and reference_z parameters.
     The twist  controls the rotation along
     with viewer's z axis.