title: Zoom out doesn´t work in orthographic projection
body: <p>I have implemented the following code in Opengl to do the zoom in and out for my model. Unfortunetly it doesn´t show as expected in orthographic projection. When I click on "+" or "-" and switch from perspective to orthogonal, then it show just one step, when I zoom in and out. When I switch from orthogonal to perspective, then It zoom in and out, when just click on "+" than it zooms in and out and the key "-" doesn´t work at all.</p>
  
  <p>Can somebody help? Thanks in advance.</p>
  
  <pre><code>glm::mat4 view = glm::lookAt(glm::vec3(4, 4, -3), glm::vec3(0, 1, 0), glm::vec3(0, 1, 0));
  glm::mat4 projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.2f, 1000.0f);
  
  float zoom = 0.5236f;
  
  case 'w':
          if (!(perspective)){
              projection = glm::perspective(zoom, 1.0f, 0.1f, 1000.0f);
              perspective = true;
          }
          break;
      case 's':
          if (perspective){
              projection = glm::ortho(-1.0f, 1.0f, -1.0f, 1.0f, -1000.0f, 1000.0f);
              perspective = false;
          }
          break;
      case '+':
  
          if (zoom &gt;= 0.0236){
              if (perspective){
                  //step of zooming
                  zoom = zoom - 0.5; 
                  zoom -= 0.1f;
                  projection = glm::perspective(zoom, 1.0f, 0.1f, 1000.0f); 
  
              }
              else{
                  //step of zooming
                  zoom = zoom - 500; 
                  zoom -= 0.1f;
                  projection = glm::ortho(-0.1 - zoom, 0.1 + zoom, -0.1 - zoom, 0.1 + zoom, -1000.0, 1000.0);
  
              }
          }
              break;
  
      case '-':
          if (zoom &lt;= 3.0236f){
              if (perspective){
                  // step of zooming
                  zoom = zoom + 0.5; 
                  zoom += 0.1f;
                  projection = glm::perspective(zoom, 1.0f, 0.1f, 1000.0f); 
  
              }
              else{     
                  //step of zooming
                  zoom = zoom + 500; 
                  zoom += 0.1f;
                  projection = glm::ortho(-0.1 - zoom, 0.1 + zoom, -0.1 - zoom, 0.1 + zoom, -1000.0, 1000.0);
          }
      }
      break;  
      }
  </code></pre>