Presumably you mean 'ambient occlusion'. There's no reason why you shouldn't do this in Carrara but it will need some experimentation. Anyhow, to start with, try this: First build yourself a shader that is white or nearly so and has no highlight or shininess. Apply that to everything in your scene. Turn off ambient light and the other lights in your scene. Now click Scene>Atmosphere and choose Sky. Change the color of the sky and ground to white and switch off the cloud layers. Flip to the Render Room and render with Skylight and Indirect light switch on. Composite this with your color/shadow/specularity passes using multiply in Phostoshop, adjusting levels to get the effect your after. HTH, Mark