Why can't I display same object in multiple viewports?

Posted by user288973 on Stack Overflow See other posts from Stack Overflow or by user288973
Published on 2010-03-12T16:03:46Z Indexed on 2010/03/12 16:07 UTC
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Hi,
I'm pretty new to OpenGL. Was playing around with some code but can't figure out why the following will not produce two viewports with the same object view. Heres the code:

glViewport(0, windowHeight/2, windowWidth/2, windowHeight);
glScissor(0, windowHeight/2, windowWidth/2, windowHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective( 45.0, (GLfloat)(windowWidth/2)/(GLfloat)(windowHeight/2), 0.1f,  
                500.0 ); 
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
drawParticleView();

glViewport(windowWidth/2, 0, windowWidth, windowHeight/2);
glScissor(windowWidth/2, 0, windowWidth, windowHeight/2);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective( 45.0, (GLfloat)(windowWidth/2)/(GLfloat)(windowHeight/2), 0.1f, 
                500.0 ); 
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
drawParticleView();

drawParticleView() just draws an array of rectangles. The problem is that the second viewport is a squashed representation of the first. My window width is 1280 and height 960. I'm obviously doing something wrong but what? Thanks

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