Porting Arcs and Circles

With OpenGL, filled arcs and circles are drawn with the same calls as unfilled arcs and circles. The following table lists the IRIS GL arc and circle functions and their equivalent OpenGL (GLU) functions.

IRIS GL Function	OpenGL Function	Meaning
arc arcf	gluPartialDisk	Draw an arc.
circ circf	gluDisk	Draw a circle or disk.

You can do some things with OpenGL arcs and circles that you can't do with IRIS GL. OpenGL calls arcs and circles, disks and partial disks respectively.

When porting arcs and circles, keep the following points about OpenGL in mind:

Angles are measured in degrees, and not in tenths of degrees.
The start angle is measured from the positive y-axis, and not from the x-axis.
The sweep angle is now clockwise instead of counterclockwise.