Shadows in C

[Lisa Pretty]

I am beginning to do a little C programming using an IRIS 4D/20
(GR1.1 Bit-plane, Z-buffer options installed).  So far, I have
been able to use different lighting models and materials to create
lighting animations with shading; however, I have not been able to
create shadows.

Is there anything in the Graphics library which will enable shadows?  If
not, could somebody point me in the right direction (I do have the
Graphics Library Manuals)?

                               Thanks in Advance

                                    Lisa Pretty
                                    uaslisa at vm.uoguelph.ca