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Thread: glRasterPos problems

  1. #1
    Guest

    glRasterPos problems

    My Problem is that every time i change the raster position when displaying a bitmap
    it dissappears it only works when
    glRasterPos2f/i(0,0) is as such, or on
    glRasterPos2f() when the change is less than
    .0001 and that does virtually nothing.
    What am i doing wrong?

  2. #2
    Senior Member OpenGL Pro
    Join Date
    Oct 2000
    Location
    Fargo, ND
    Posts
    1,753

    Re: glRasterPos problems

    A couple of things to check.

    1. If the raster position is set to something not visible, and you try and use it to draw a bitmap, none of the bitmap will show up.

    2. When setting the raster position, it is modified by the current model-view and projection matrices, so if you are doing transforms that will make it go out of your viewing volume, you won't get your bitmap displayed.

    One thing you could do would be something like so...

    // Set matrix mode
    glMatrixMode(GL_PROJECTION);
    // push current projection matrix on the matrix stack
    glPushMatrix();
    // Set an ortho projection based on window size
    glLoadIdentity();
    glOrtho(0, width, 0, height, 0, 1);

    // Switch back to model-view matrix
    glMatrixMode(GL_MODELVIEW);

    // Store current model-view matrix on the stack
    glPushMatrix();

    // Clear the model-view matrix
    glLoadIdentity();

    // You can specify this in window coordinates now
    glRasterPosition2f(x,y);

    DrawYourBitmap();

    // Restore the model-view matrix
    glPopMatrix();

    // Switch to projection matrix and restore it
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();

    // Switch back to model-view matrix. This isn't
    // strictly necessary, but I tend to try and
    // keep the model-view matrix as the current
    // matrix to keep things simple.
    glMatrixMode(GL_MODELVIEW);
    Deiussum
    Software Engineer and OpenGL enthusiast

  3. #3
    Guest

    Re: glRasterPos problems

    Works Perfectly Now, Thanks a lot.

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