title: Setup Orthographic projection correctly?
body: <p>Recently I need to use orthographic projection using glm library. But with orthographic projection my scene is not rendering at the center of my viewport. </p>
  
  <p>My Scene is simply a cube, It was rendering well by using glm::perspective. I don't understand too much mathematical stuff, I just using glm::ortho function. </p>
  
  <p>So how do I need to do to correctly setup the orthographic projection? </p>
  
  <p>Here is the code I did:</p>
  
  <pre><code>mat4 projection=ortho(0.0f, 800.0f, 600.0f, 0.0f,-1000.0f, 1000.0f);
  mat4 view=lookAt(vec3(0,0,1),vec3(0,0,0),vec3(0,1,0));
  mat4 model=mat4();
  </code></pre>
  
  <p>Then I sent these three matrices to shader which is same as perspective projection did.It should be a quad in the center of my screen, but in my program it is lied on the top left corner of the screen,turns out like the a quarter.</p>