Ambient Occlusion

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Ambient Occlusion (AO) is a local shading effect that will darken regions of concavity on a surface and brighten convex areas.

There are several places in mr and 3ds Max where you can enable AO:

1. There is an Ambient/Reflective Occlusion (base) shader that you can use in any normal map slot, or in a Material Override material if you want all objects in the scene to have the same AO material.
2. The Arch & Design material has a built-in AO effect in the 'Special Effects' rollout
3. If you assign an AO shader to a light, all objects in the scene will receive that effect

Ambient occlusion through a light source

This is also known as the AO Omni light trick:

1. Create an omni light exactly at position [0,0,0] with rotation [0,0,0] (e.g. create it in the top viewport)
2. Set the light to 'Ambient Only'
3. Assign an Ambient/Reflective Occlusion (base) shader as the light's projector map

All objects will now get extra AO illumination. If you do not have any other active light source in the scene, you will get a pure AO pass (but with all materials still present; if you don't want your materials, use the Material Override option in the Processing tab of the render dialog)

External links

• Ambient occlusion pass guide by Ziv Qual
• Using Ambient Occlusion to enhance render details by Everflow
• Mental Ray - Ambient Occlusion Shader by Cg Academy
• Ambient Occlusion Shader by Mastering Mental Ray