I’m having problems porting the IRIS GL command lookat into the OpenGL gluLookAt.

The lookat work as:

lookat(vx, vy, vz, px, py, pz, twist)

where: vx, vy,vz are the coordinate of the viewing point,

px, py,pz are the coordinate of the reference point,

twist is the angle of rotation (measures right-hand rotation about the line of sight).

I need a way to convert the twist angle to the upX, upY, upZ values of the direction of the up vector in gluLookAt fonction.