Depending on your source, select which Method to use:

• From Displacements information.
• From Normals in a normal map file.

This selection will influence what will appear in the Source drop menu, right below.

Now select the actual source map by clicking in the Source drop menu.

You can choose to:

• Use a currently open map.
• Open from a file in your computer.
• Paste an image from the Clipboard.
• Drag'n'drop a file into the tool area (not into the Editor).

After selecting the source image, AO computation will automatically start.

The extracted image will be of the same Width and Height as the source image. If by chance an AO map is already open and is of different size, a window will appear asking which size to keep.

After AO computation starts, a new slider will appear allowing you to tune the result.

Use the Ray Distance slider to control the pixel distance up to which ambient occlusion can affect a point in the image. Smaller distances result in smoother AO maps as there's less chance for occlusion at shorter distances. But to obtain good occlusion of larger features you'll need to increase the Ray Distance.

Try different ray distances to see this kind of "feature tuning" in action.

If needed, the extracted displacement can further refined or retouched with the other tools available, like the Adjust or even the Paint tools.

You may want to see the following video tutorial about automatic map extraction:

Extracting 3D Maps