Category: mental ray > Texture
This shader is an alternative to the mib_amb_occlusion shader, with similar functions, but fully utilizing the ambient occlusion facilities built into mental ray. This shader offers optimal rendering performance and the possibility to benefit from the ambient occlusion cache, if enabled.
This shader cannot be used as a light shader.
Name |
The name of the shader node displayed in the render tree. Enter any name you like, or leave the default. |
samples |
The number of probe rays that are sent. More rays yield a smoother image. If the ambient occlusion cache is enabled, this parameter is ignored: the number of points to use for cache interpolation is controlled by the cache_points option. |
bright |
The color used when no occluding objects are found. For partial occlusion, a gradual mix between this color and the dark color is returned. |
dark |
The color used when total occlusion occurs. In most practical cases, it is set to black. |
spread |
Defines how large an area of the hemisphere above the point is sampled. Unlike the mib_amb_occlusion shader, this value is the cosine of the angle between the normal and the maximum direction. Its value ranges from 0.0 for a cone that covers the entire hemisphere to 1.0 for a cone that is a single direction. |
spread_exp |
The exponent of the spread angle. It controls how the rays shot from the sampling point are concentrated around the normal. A higher value means more density around the normal. This parameter is not currently supported by mental ray, but is provided for future versions. |
max_distance |
The range within which geometry is probed. If it is zero, the entire scene is sampled. If it is a non-zero value, only objects within this distance are considered (which makes sampling much faster). Objects outside this range do not occlude at all, and objects that are closer occlude more strongly as the distance approaches zero. |
reflective |
If this option is off, sampling is performed in a cone area based around the surface normal. If this option is on, the samples are instead distributed around the reflection direction. This generates reflective occlusion which can greatly enhance the realism of reflection mapping. |
output_mode |
Defines what the returned color is:
|
occlusion_in_alpha |
Puts the scalar occlusion value in the returned color's alpha component, regardless of what is set for output_mode. The other color components remain as before. |
cache_points |
Controls the number of ambient occlusion points to lookup for interpolation in the ambient occlusion cache. If the the cache is not enabled, this option is ignored. A value of 0 means the number of ambient occlusion points are determined by mental ray settings. Values greater than 0 override the setting for the current object. Values smaller than 64 give more precise results, but artifacts can appear. Higher values tend to produce a blurry image. |
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