Re: openGL problem

From: Richard Harke (rharke_at_earthlink.net)
Date: 06/27/05

  • Next message: Dances With Crows: "Re: openGL problem" 
    Date: Mon, 27 Jun 2005 05:39:24 GMT

    Dances With Crows wrote:

    > On Sat, 25 Jun 2005 20:54:14 GMT, Richard Harke staggered into the Black
    > Sun and said:
    >> I am trying to draw a hyperbola. I have very simple code to draw the
    >> three axes and that displays. if I add a call to sinh and cosh to
    >> calculate a point on the hyperbola, I get nothing, not even my
    >> coordinate axes.
    >
    > You Mean "if I *draw* the points I receive from sinh() and cosh(), I get
    > a black screen", right? You may wish to fprintf() the values you're
    > getting from sinh() and/or cosh() to stderr, just to make sure the
    > functions aren't returning "domain error" or "range error" or NaN or
    > something that isn't what you're expecting.
    >
    >> Window opens but is just the background. Some times white, correct.
    >> some times black which is wrong. I rearranged code so calls to sinh
    >> and cosh are not between glBegin and glEnd -- doesn't help.
    >
    > No, it wouldn't, not really.
    >
    >> Either way, calls to sinh and cosh are in the display callback
    >> Video is Nvidia FX5300 (5200 with PCI Express)
    >> Using Nvidia's driver 6111
    >>
    >> Any one have a clue??
    >
    > (POVRay terminology, sorry, I don't know the OpenGL equivalents, but the
    > concepts should transfer.)
    >
    > If this is 3D, you need to make sure the shape you're drawing isn't
    > between the camera and the light source. Try restricting the X..Y range
    > from -1..1 and moving the camera to 1.5,1.5,1.5 look_at 0,0,0. If that
    > works more like what you want, you've got a camera positioning problem.
    > POVRay warns you if the camera is inside an object, but I'm pretty sure
    > OpenGL won't. HTH anyway,
    >
    Thanks for your reply. I know my image is in the right place
    wrt the camera because with the calls to sinh and cosh it is fine.
    I can substitute an expression using calls to exp and get the image
    I want. But it also appears that the problem has nothing to do
    with openGL but something is badly wrong with sinh and cosh.
    I have tried a little test program with no openGL, just printf.
    The expression with exp is fine but sinh and cosh give crap.
    But if I have a call to sinh or cosh in the same program with the
    expression using exp, then that returns crap as well.
    I guess I need a more appropriate forum to follow up.

    Richard

  • Next message: Dances With Crows: "Re: openGL problem"

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