TYPE: VOP
TITLE: Shading Layer Parameter VOP

This operator creates a parameter to appear in the signature of the VEX function
defined by the VOP network (VOPNET). The new parameter is named according to
the chosen geometry attribute and the specified layer.

Unlike the Parameter operator, which creates parameters of any name and type,
Shading Layer computes the parameter name from the name of the geometry
attribute and the specified layer. For example, choosing "UV Coordinates" from
the attribute menu will generate "uv, "uv2", "uv3" when the layer is 1 and
respectively 2 and 3. The parameter type matches the type of the selected
geometry attribute.

This operator always checks if the geometry attribute is bound and, if so,
assigns its value to the new parameter. Thus, the new parameter will be hidden
in the operator type defined by the VOP network.

One of the most common uses of this operator is the creation of layered
textures, which requires different sets of texture coordinates for each Texture
operator. To accomplish this task, choose "UV Coordinates" from this operator's
attribute menu and set the appropriate layer. Pipe the "uv" output into a Vector
To Float operator to extract the "s" and "t" as individual float values, then
wire "s" and "t" into the Texture operator. Repeat this operation for all the
layers, then add or multiply the all Texture outputs using the Add or Multiply
operator respectively.

Parameters:
    Geometry Attribute - The attribute to be searched for in the given layer.
                         The following attributes are available in this operator:

	      ~c(
              Label          | Name  | Type     | Default If Not Bound
              ---------------+-------+----------+---------------------------
              UV Coordinates | uv    | 3 floats | { global s, global t, .5 }
              RGB Color      | Cd    | 3 floats | { 1, 1, 1} (i.e. white)
              Alpha          | Alpha | 1 float  | 1          (i.e. opaque)
	      ~c)

              Geometry attributes are created in the Geometry module using a
              variety of SOP operators such as: AttribCreate, Attribute, Point,
              UV Project, UV Texture, UV Unwrap, etc.
    Attribute Layer  - Attribute layer where to search for the geo attribute.
              Layer 1 is the default layer. Attributes in this layer do not have
              a suffix. Layers are created in the Geometry module using the
              Layer SOP.
    Export Parameter - Specifies whether the new parameter can be exported to
              other contexts (written to as well as read from). If true, this
              operator gets an input. The value wired into this input is then
              assigned to the exported parameter. In a Surface network, for
              example, exported parameters can be used to create deep rasters.

Inputs:
    Export Value       - The value assigned to the new parameter if the "Export
                         Parameter" toggle is checked.

Outputs:
    Output Parameter   - The value of this VEX function parameter.
    Is Parameter Bound - True is the new parameter is bound to an attribute.

See also: Constant, Global Variables(global), Parameter,
          UV Space Change(uvspacechg)
