title: glm::unProject issues, world to screen space alignment error
body: <p>I have a plane in 3D space, which is facing the camera that I want to be able to place at the same position as where I click. However, the position of the plane overshoots the mouse cursor. This is for a dynamic GUI that I want to be able to move about and interact with the widgets on the UI.</p>
  
  <pre><code>void mouse::unProjectMouse(float width, float height, camera* viewportCamera)
  {
      if(NULL == viewportCamera)
      {
          std::cout&lt;&lt;CNTRLCALL&lt;&lt;"camera failed! failed to un-project mouse";
      } else {
          glm::vec4 viewport = glm::vec4(0, 0, width, height);
          glm::mat4 tmpView = viewportCamera-&gt;updateView();
          glm::mat4 tmpProj = viewportCamera-&gt;updateProjection();
          glm::vec3 screenPos = glm::vec3(mouseX, height-mouseY - 1.0f, 1.0f);
  
          glm::vec3 worldPos = glm::unProject(screenPos, tmpView, tmpProj, viewport);
  
          worldPos = worldPos / (worldPos.z * -1.0f);
  
          mouseWorldX = worldPos.x;
          mouseWorldY = worldPos.y;
          mouseWorldZ = worldPos.z;
      }
  }
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/BwItH.png" alt="Here we see the mapping from viewport coords to world coords"></p>
  
  <p>I am at a loss here as to why the plane is not aligning correctly with the mouse.</p>