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Thread: glEvalCoord

  1. #1
    Guest

    glEvalCoord

    Hello,
    I'm trying to determine how I can get the
    vertices produced by 'glEvalCoord1f'...
    Of course, I already have the control points.
    It's the points that are on the curve
    generated which I need.
    All help is aappreciated. Thanks!
    Jon

    I'm using the example from Chap12 (redbook)
    as follows:

    glMap1f(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, 7, &ctrlpoints[0][0]);
    glEnable(GL_MAP1_VERTEX_3);
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(0.5, 0.5, 0.5);
    glBegin(GL_LINE_STRIP);
    for (i = 0; i <= 30; i++)
    {
    glEvalCoord1f((GLfloat) i/360.0);
    }
    glEnd();

  2. #2
    Senior Member OpenGL Pro
    Join Date
    Oct 2000
    Location
    Fargo, ND
    Posts
    1,797

    Re: glEvalCoord

    I'm not sure if there is any way to get them directly, except possibly through use of the feedback buffer. I haven't really done much with the feedback buffer, however.

    Another option would be to examine the formulas that OpenGL uses to calculate the points. I believe they are described in the OpenGL specification. You could then use those formulas directly to calculate the results.
    Deiussum
    Software Engineer and OpenGL enthusiast

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