Con esto podemos reducir considerablemente los tiempos de render 
Podemos ver el artículo completo en http://mpan3.homeip.net/page?ssaowcn
Limitations:
- NOT physically accurate! Only yields good results when used lightly in combination with textures.
 - Huge Z differences cause problem. This can be seen at edges where the mesh meets the sky.
 - Intensity is entirely dependent on the difference in Z value and not the normal rotation of the face.
 Advantages:
- Very generalized setup that works relatively well for all scenes.
 - Several hundreds times faster than ray-traced AO.
 - No other setup required other than the nodes.
 - Independent with camera clip values ·
 - Polygon count independent: can process a scene with 10 million polygon in 1 second.