Doing Ambient Occlusion in every material in a scene is normally not necessary. After reading this post in Caffeine Abuse I started using it as a Lens shader, but noticed the render got darker. It was because I’m using linear workflow in Softimage, so I had to update the compound a little bit:
Just drag & drop the file into Render Tree, or move it to the Data/RTCompounds folder in your User or Workgroup directories. To apply it just connect it to the Camera as a Lens Shader.
Caffeine Abuse is an incredible place for Softimage tutorials, tips & tricks. All credits of this shader are to it, I’ve just packed it up and added the gamma support. .