2D Drawing in OpenGL

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Posts: 133
Joined: 2008.05
Post: #1
I want to draw something that isn't 3D at all. I guess I'd like to draw something without any projection, kind of like "in the front" of the screen. So when I draw something with the coordinates -.5,.5 as left corner and 0,0 and the bottom right corner, I'd like it to cover exactly 1/4th the screen, the second quadrant. I also need to do this after I draw some projected stuff.

I'm guessing it would have to do something with setting up another camera orthographically, then pushing the matrix calling the camera render function, and drawing?
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Posts: 156
Joined: 2002.11
johnMG
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Post: #3
Using glut, I wanted the dimensions of my drawing area to match up with the actual pixels, so I did this:
Code:
void my_reshape_func( int w, int h )
{
    glViewport( 0, 0, w, h );
    
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    glOrtho( 0.0, static_cast<double>( w ),
             0.0, static_cast<double>( h ),
             -1.0, 1.0 );

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();
    
    glutPostRedisplay();
}

You'll need to pass something different than w & h to glOrtho() if you don't want (0.0, 0.0) to be the bottom left corner. Enjoy. :)
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