The incidence parameter defines the angle of incidence in the y,z plane, measured in distance from the z axis.
The swf_polarview() function defines the viewer's position in polar coordinates. The dist parameter gives the distance between the viewpoint to the world space origin. The azimuth parameter defines the azimuthal angle in the x,y coordinate plane, measured in distance from the y axis. The incidence parameter defines the angle of incidence in the y,z plane, measured in distance from the z axis. The incidence angle is defined as the angle of the viewport relative to the z axis. Finally the twist specifies the amount that the viewpoint is to be rotated about the line of sight using the right hand rule.