Ambient Occlusion (MR) Map (mental ray Renderer Only)

Use an ambient occlusion map when you want the surface information to describe how much ambient light the surface can receive.

Note: This map is available only when the mental ray renderer is active.

The Ambient Occlusion map considers the obstruction of the light by surface contours and surrounding objects. By using the Ambient Occlusion map when rendering, you do not need to set up special lighting, replace materials on the objects, or use with global overrides because the Ambient Occlusion map already accounts for these settings.

You can use Ambient Occlusion maps with or without a Projection modifier and for many different purposes. Use them to mask layers in Adobe Photoshop, for items such as painted edits and texture maps. Also use them as dirt maps, or as masks for reflections or specular light.

Note: By default, the shader used by the Ambient Occlusion baked element excludes the low-resolution object from the ambient occlusion calculations whenever performing projection-mapped texture baking. However, if the Projection Mapping option Include Working Model is turned on, then the occlusion rays will include the working model. In this case, projection rays also include the working model. No undesired blank areas appear on the map, because there are no cases where a projection ray passes though the lo-res model to hit a point on the high-res model that is completely occluded by the low res.

Original scene surrounded by rendered-to-texture ambient occlusion maps of the floor object

Top left: Samples=8; Spread=0.8

Top right: Samples=32; Spread=0.8

Bottom left: Samples=16; Spread=0.5

Bottom right: Samples=16; Spread=0.99

Selected Element Unique Settings

For an ambient occlusion map, you can set the following unique settings:

Samples

Sets the number of rays cast. More rays results in a smoother image. Default=16.

Spread

Sets the spread of the ray, creating a cone shape. With a value of 0.0 a single point is sampled; with a value of 1.0 the entire hemisphere is sampled. Range=0.0–1.0. Default=0.8.

Note: You can set Spread to values greater than 1.0, but only values within the specified range are useful.

Bright

Sets the color in the map where no occlusion occurs. The default color is white. Click the swatch to change the color.

Dark

Sets the color in the map where complete occlusion occurs. The default color is black. Click the swatch to change the color.

Note: Colors between the Bright and Dark values are used to indicate partial occlusion.

Max Dist[ance]

Sets the range within which geometry is probed. A value of 0.0 samples the entire scene. For non-zero values, only objects within this range are sampled. Default 0.0.

Falloff

Defines the amount of falloff of the ray. The greater the value, the greater the falloff. Default=1.0.