Ambient Occlusion

The decision to use ambient occlusion was a simple one. Every render looks significantly better with a ambient occlusion pass, it creates shadows where objects or models meet.
I have done a quick test to see the difference with and without this pass.

This is the image from the ambient occlusion pass, this is the default settings for a quick test, when i come to create this pass i will change the settings until i am happy with the result:

This is a render from the normal, usual pass. Nothing has been changed it is just a screen render taken from the camera view (same position as the ambient one):

This one is the two put together, as you can see the scene looks so much better. The shadowing really helps to show that the objects are placed together:

Process
I always struggle to remember how to create this pass so i'm going to write it down so i can refer back to it later on.

Taken from the Softimage User's Guide:
http://download.autodesk.com/global/docs/softimage2012/en_us/userguide/index.html?url=files/lights_AO_ConnectingtheAmbientOcclusionShader.htm,topicNumber=d28e364681

Here's a quick overview of how to create an ambient occlusion pass.

1. From the Render toolbar, choose Pass  Edit  New Pass  Empty.
2. Make the new pass current.
3. Select all the geometric objects that you want to include in the ambient occlusion effect. Make sure that you branch select the models and hierarchies so that nothing is omitted. You can do this in the explorer by Ctrl+middle-clicking each object.
4. From the Render toolbar, choose Pass  Partition  New Partition to create a partition that includes all the objects that you previously selected.
5. In the explorer, set its scope to Passes and select the partition you created (it's nested under the ambient occlusion pass).
6. From the Render toolbar, choose Get  Material  Ambient Occlusion to apply it to the new partition displayed in the explorer.
7. The XSIAmbientOcclusion shader's property editor opens. Pin the property editor open and set the options as needed. See Setting the Ambient Occlusion Shader Options.
8. Draw a render region to preview the effect.
9. From the Render toolbar, choose Render  Regions  Active Viewport Options and set the mental ray ambient occlusion options for the region.
10. When you are happy with the settings, you can copy them from the render region to the current pass in order to render the effect as previewed.
11. Make sure that the ambient occlusion pass is still current and choose Render  Regions  Region Copy  Active Viewport To Current Pass from the Render toolbar.
12. Choose Pass  Edit  Edit Current Pass and set the output options for the render pass. See Pass Rendering Options Overview [Rendering].
13. Choose Render  Render  Current Pass to render the ambient occclusion pass.