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Thread: about cullfacing

  1. #1
    Junior Member Newbie
    Join Date
    May 2001
    Posts
    21

    about cullfacing

    hi there

    could somebody explain me what openGL actually does when cullfacing? does it test all polygons described in the scene?

    thanx

  2. #2
    Senior Member OpenGL Guru
    Join Date
    Feb 2000
    Location
    Sweden
    Posts
    2,978

    Re: about cullfacing

    For every triangle you pass to OpenGL, it determines the winding order of the vertices (clockwise or couner clockwise) when projected on the screen. If they are ordered "the wrong way", the triangle is thrown away.

    "The wrong way" means different thing depending on how you setup the culling. For example, if you say a front face is CCW, and you want to cull all back faces (a backface is then CW), OpenGL will remove all triangles whose vertices are projected CW on the screen.

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