OpenGL, quads not displaying

This is a discussion on OpenGL, quads not displaying within the Game Programming forums, part of the General Programming Boards category; sorry i wasnt using glMatrixMode(...); problem fixed now, on another note, can someone explain to me whether using glOrtho means ...

  1. #1
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    OpenGL, quads not displaying

    sorry i wasnt using glMatrixMode(...); problem fixed now,

    on another note, can someone explain to me whether using glOrtho means i should remove glMatrixMode or if setting the orthographic view is entirely separate from the matrix mode? and which matrix mode should i use if this is the case? I'm making a 2d game and want the view to look like that of super smash bros on a platform

    thanks
    Last edited by Astra; 07-03-2011 at 07:38 AM.

  2. #2
    Unregistered User Yarin's Avatar
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    glMatrixMode just makes a selection, it doesn't do anything in of itself.
    glOrtho will "multiply the current matrix with an orthographic matrix"
    glOrtho's counterpart is glFrustum, which will "multiply the current matrix by a perspective matrix".
    In a fully 2D game, and orthographic view would probably be best.

  3. #3
    Frequently Quite Prolix dwks's Avatar
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    You probably shouldn't edit away an existing post, it makes the thread hard to read and it's just disconcerting. Also if you have a new question, placing it in a new post will enable others to see that the thread has changed. I'd say that editing should be reserved for fixing typos and adding clarifications.

    glOrtho() "[multiplies] the current matrix with an orthographic matrix" according to the docs. So in order to have it affect your viewport you need to apply it to the GL_PROJECTION matrix. (Essentially it's just like a glMultMatrix() call, which of course applies to the matrix corresponding to the current matrix mode.) And most other operations use GL_MODELVIEW so you should switch back after you call glOrtho(). So generally you'd use something like
    Code:
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(...);
    glMatrixMode(GL_MODELVIEW);
    You could have found that out in about forty-six seconds by googling "glortho example", by the way.
    dwk

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