When using the mib_amb_occlusion shader
to perform an occlusion pass, you can choose to exclude one or more
objects from the occlusion calculations.
Do one of the following:
Method 1: Hide
- Use this method if the object in question
does not need to be involved in other trace calls such as reflection
and final gather.
In the object's transform
node, expand the mental ray section. In the Flags section,
disable Derive From Maya and turn on Hide.
Method 2: Adding miLabel
- Use this method if the object in question
must be involved in other trace calls such as reflection and final
gather.
- Add a mental ray label to all transforms
that need to be excluded from the ambient occlusion calculations.
For example, assuming
that $targetTransform is
your transform, set the miLabel as
follows:
addAttr
-at short -longName miLabel -defaultValue <your value> $targetTransform;
NoteSet the miLabel to a value that is unique to
your scene. In other words, select a value that is not currently
being used for other mental ray labels in your scene.
- Set the id_inclexcl attribute
in the mib_amb_occlusion node
to the same absolute value as your miLabel.
For example, if you set your miLabel to
8, your id_inclexcl value
must also be set to -8.
NoteYou can set the
id_inclexcl to either a positive or
negative value. Set it to a positive value so that only object instances
with a label that matches this number are included in the occlusion
render. Set it to negative so that all object instances that match
this number are excluded from the occlusion render.
For example, if you set
your id_inclexcl value
to 8, then only transforms with a miLabel of
8 are included in the occlusion render.
If you set your id_inclexcl value to -8, however, then
all transforms with a miLabel of
8 are excluded from the occlusion render.
See the mental
ray for Maya shaders guide for more information about
the mib_amb_occlusion node.