title: Use top-left origin in OpenGL
body: <p>I am trying to set my co-ordinate system such that the y-axis points down the screen.</p>
  
  <pre><code>// Determine view-projection matrix
  glm::mat4 projection = glm::ortho(
      -3.0f,    // left
      3.0f,     // right
      3.0f,     // bottom
      -3.0f);   // top
  
  // Right handed rule:
  // x points right
  // y points down
  // z points into the screen
  glm::mat4 view = glm::lookAt(
      glm::vec3(0, 0, -1),    // camera position
      glm::vec3(0, 0, 0),     // look at
      glm::vec3(0, -1, 0)     // up vector
  );
  
  glm::mat4 viewProjMatrix = projection * view;
  </code></pre>
  
  <p>However, when I try to render 2 objects:</p>
  
  <pre><code>A at (0, 0)
  B at (1, 1)
  </code></pre>
  
  <p>A appears in the centre of the screen, and B appears in the top-right. I would expect it to appear in the bottom-right.</p>
  
  <p>What am I missing here?</p>