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Extract an ambient occlusion map

Ambient occlusion is a shading effect that calculates the attenuation and occlusion of light between surface details and other objects in the scene and then adds realistic shading to models.

You create ambient occlusion maps using the Maps > Extract Ambient Occlusion Maps feature. It calculates the ambient occlusion map based on the spatial relationships between various items in the scene and creates a diffuse image map that is automatically applied to the model(s) as a paint layer so you can preview it before importing the texture map into another 3D application.

This feature provides a method for generating ambient occlusion image maps on extremely high resolution models, in a variety of file formats, that would otherwise be difficult to achieve using other 3D applications.

NoteWhen extracting ambient occlusion maps on multiple objects simultaneously in the 3D View each object should be assigned its own separate shading material. Otherwise, the extracted map assigned to the default material (which is assigned to all objects by default) appears on all objects in the scene when you preview it. The exception for this is when extracting a map from an asset that is comprised of multiple objects and whose UVs are laid out in multiple UV tiles. In these situations, assigning the same material to all objects is required.

Ambient occlusion maps can also be edited and enhanced directly in Mudbox, if necessary, using the 3D paint tools.

1. Select Maps > Extract Ambient Occlusion Maps > New Operation.

   The Extract Ambient Occlusion window appears. For a complete description of extraction properties see Extract Ambient Occlusion Maps properties.

2. Indicate the model(s) you want an ambient occlusion map for by selecting its name in the Object List or in 3D View using the Objects selection tool (located on the Select/Move Tools tray).
   NoteIf a model is not selected then an ambient occlusion map is produced for all objects in the 3D View. Keep in mind that all visible objects in the 3D View are taken into account when calculating an ambient occlusion map. That is, if you don’t want an object to be included as part of the ambient occlusion calculations, hide it before extracting a map.
3. Press either the Page Up and Page Down keys to set the desired subdivision level on the model(s) that you want the extraction to occur.

   Setting the subdivision level on the model to its highest subdivision level provides the most detailed ambient occlusion map possible. It is possible to extract a map at lower subdivision levels, but fine detail will not be extracted in the map and the appearance of facets because of the lower resolution may result.

4. In the Extract Ambient Occlusion window, adjust any properties as required and click Extract:
   NoteThe model must have UV texture coordinates to extract an ambient occlusion map. Otherwise, the following message appears when you click Extract: The model mesh has no UVs. Mudbox needs UVs to generate Ambient Occlusion Maps. Try selecting Recreate Level UVs under the Mesh menu. For more information, see UVs overview.
   - Quality - Determines the quality of the final ambient occlusion map based on multiple shadow maps that get used for the calculation.
   - Image Size - Specifies the height and width (in pixels) of the ambient occlusion map(s) output.
   - Base File Name - Specifies the name of the extracted map(s).
   TipThe first time you extract an ambient occlusion map, set the Quality setting to Fastest and Image Size to a small resolution to quickly generate a test map. Evaluate this initial test, adjust any settings as required, and then set the Quality and Image Size options to the final settings before generating a final map.

   The Advanced section, contains the following properties:

   - Shadow Map Resolution - Controls the size of the shadow maps for the occlusion map calculations.
   - Add as Paint Layer - Automatically imports the generated ambient occlusion map as a new paint layer within the Diffuse channel of the assigned material. Turn this setting off if you don’t want the ambient occlusion map assigned to a new paint layer.
   - Shadow Darkness - Controls the darkness of the shaded regions in the final ambient occlusion map.

   - Shadow Contrast - Controls the contrast between shaded and non-shaded areas in the ambient occlusion map.

   - Filter - Controls the filtering of the multiple shadow map calculations when producing the final ambient occlusion map. To achieve sharp, finely detailed shadows, set the Filter value to a low number (0.0001). To produce a softer effect, set the Filter value to a higher number.

   - Bleed Width - Specifies the width of the pixel border that automatically gets added along the outside perimeter of each UV shell on the extracted map. This reduces the possibility of seams occurring on the extracted map where shell borders meet. The default width is one pixel.

   - Skip Back Lights - Lights situated behind the surface are not taken into account by the ambient occlusion calculations when this option is turned on. Otherwise back facing lights may affect the output. When on, this feature provides the best extraction results under most circumstances. The default is on.

A progress bar on the Status Line indicates the progress of the extraction. Depending on the Quality setting, this bar may repeat the process several times as the feature calculates and composites the necessary shadow maps.

The ambient occlusion map is automatically applied to the model(s) as a diffuse paint layer (provided the Add as Paint Layer property is turned on) and positioned on top of any other existing paint layers in the Diffuse channel.

If the model contains UVs within multiple UV tile spaces, that is, outside the 0 to 1 range, the feature automatically creates separate ambient occlusion maps that correlate to each UV tile and saves them to the user-specified directory.

NoteIf your model contains multiple UV tiles, each tile will appear in a different color after the ambient occlusion map is applied to indicate that the textures are currently unloaded. This is a graphics memory optimization feature. For more information, see Hide and show UV tiles on a model.

Edit an ambient occlusion map

Once an ambient occlusion map has been created and applied as a visible paint layer, you can evaluate it and then make successive iterations by changing the extraction settings then clicking extract, and previewing the updated version again.

If you extract successive ambient occlusion maps with the same file name it overwrites the previous one and the paint layer is automatically updated in the 3D View with the new map.

You can use the Paint tools to modify or enhance the ambient occlusion map (add shading, erase shading, and so on) because the map is applied a diffuse paint layer.

Related topics

Extract Ambient Occlusion Maps properties