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Thread: drawing outerlines for concave polygons

  1. #1
    Junior Member Newbie
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    drawing outerlines for concave polygons

    hi,
    i rendered the filled concave polygons by tesselation.now i have to draw outerlines for those filled polygons. can any one help me for this, so that i'll be thankful to you.
    thanks and regards
    k.bhogasena reddy

  2. #2
    Senior Member OpenGL Pro
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    Re: drawing outerlines for concave polygons

    On Windows, check out wglUseFontOutlines. I think it uses one of the "plane sweep" algorithms to triangulate the contours.

    Or maybe have a look at one of the (platform neutral) font generation/rendering libraries out there. I've seen several mentioned in recent threads.

    Hope it helps.

  3. #3
    Member Contributor
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    Re: drawing outerlines for concave polygons

    Use GL_LINE_LOOP with the original Polygon Points?

  4. #4
    Member Newbie
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    Re: drawing outerlines for concave polygons

    I would draw the polygon twice. The first time in the normal way and the second time, using glPolygonMode (GL_LINES) and with using wider lines (I think with using glPointSize).

  5. #5
    Member Contributor
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    Re: drawing outerlines for concave polygons

    Hm ok whats wrong here ...
    > using glPolygonMode (GL_LINES)
    > using glPointSize
    use LineWith and this can also be a solution BUT
    you also draw the triangeles inside the polygon. But if you use Z-Buffer and polygonoffset you can remove the "wrong" lines inside ...

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