Subject: Common errors

(This message is being sent to CPSC 215 Students and TA's)


(1) failure to set the "hits" function pointer in fplane_init()

    When you call plane_init, it will set the
    hits function pointer in the obj to plane_hits.

    You MUST override this by setting it to
    fplane_hits() in fplane_init AFTER the return
    from plane_init.

    If you fail to do this you will have just turned your
    finite plane into an infinite plane

(2) x - y coordinate confusion

    There were several of these reported by me on mp1.  At
    least one student apparently thought (incorrectly) that
    he had fixed the problem.

    If your program appears to run correctly if and only if
    you use SQUARE PIXMAPS, then you have this problem.  I
    always test using a 4 x 3 aspect ratio.

    The sample output images are produced in this fashion.
    DON"T WASTE TIME rendering square pixmaps.