title: first person camera, turning around OPENGL
body: <p>I have a perspective camera with Obs and VRP and Up vector.</p>
  
  <p>I want to implement turning around to act like an observer inside my scene. I have already implemented forward and backward as it is only adding same amount to z coordinate to Obs and VRP (both are vec3).
  The problem comes when I try to implement rotate, 
  is there any way to do it with matrix product? I've tried that:</p>
  
  <p>x = R * cos angle</p>
  
  <p>z = R * sin angle</p>
  
  <p>where R is the magnitude of vector (VRP - Obs) but it doesn't work</p>
  
  <p>Edit: i apply view and projection matrix here:</p>
  
  <pre><code>    void MyGLWidget::projTransform(){
      //fov window, ra window (anchura / altura), near, far
      glm::mat4 Proj = glm::perspective(M_PI/1.3, 1.0, 0.2, 3000.0);
      glUniformMatrix4fv(projLoc,1,GL_FALSE, &amp;Proj[0][0]);
  }
  
  void MyGLWidget::viewTransform(){
      //lookAt(OBS,VRP;UP)
      //glm::mat4 View = glm::lookAt(glm::vec3(0,0,10),glm::vec3(0,0,-2), glm::vec3(0,1,0));
      glm::mat4 View = glm::lookAt(glm::vec3(xObs,yObs,zObs),glm::vec3(xVRP,yVRP,zVRP), glm::vec3(0,1,0));
      glUniformMatrix4fv(viewLoc,1,GL_FALSE, &amp;View[0][0]);
  }
  </code></pre>