title: Tweak the brightness/gamma of the whole scene in OpenGL
body: <p>Does anyone know how I can achieve the following effect in OpenGL:</p>
  
  <ul>
  <li>Change the brightness of the rendered scene</li>
  <li>Or implementing a Gamma setting in OpenGL</li>
  </ul>
  
  <p>I have tried by changing the ambient parameter of the light and the type of light (directional and omnidirectional) but the result was not uniform. TIA.</p>
  
  <p>Thanks for your help, some additional information:
    * I can't use any windows specifics API.
    * The gamma setting should not affect the whole window as I must have different gamma for different views.</p>