[Oberon] System-V - Frame Clipping

Jörg joerg.straube at iaeth.ch
Mon Mar 4 10:06:44 CET 2019


    >Before implementing clipping in HW you would have to implement these

    >primitives in HW.


    Did you mean these primitives implemented in SW [HW], to clip them in



No. HW primitives can be clipped in HW or SW. SW primitives to be clipped in SW.


    My naive idea of HW clip would be, to populate HW registers with F.X,

    F.Y, F.X+F.W, F.Y+F.H.


    Then some `magic' address calculation blocks will let through to

    display buffer only certain mem access. Nothing to be drawn outside



Unfortunately, that's not easily possible, as memory wraps around from line to line.  A simple test "if point is inside allowed region" is not enough.

For HW to clip, you need a Line primitive in HW. A simple Dot primitive in HW checking for memory bounds is not enough.




    Tomas Kral <thomas.kral at email.cz>


    Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related systems



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