Thread: OpenGL, quads not displaying

  1. #1
    Registered User
    Join Date
    Oct 2006

    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

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

  2. #2
    Unregistered User Yarin's Avatar
    Join Date
    Jul 2007
    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
    Join Date
    Apr 2005
    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
    You could have found that out in about forty-six seconds by googling "glortho example", by the way.

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