TYPE: SOP
TITLE: AttribTransfer SOP

AttribTransfer is used to transfer vertex, point, primitive, and/or detail
attributes between two selections.

The attributes may be explicitly specified in the corresponding attribute text
field. Exclusion is specified by preceding an attribute name with the carat
character (^). All available attributes can be specified by leaving the field
blank or entering an asterisk (*) in the field. If the first attribute is
preceded by a carat then all attributes are assumed to be transferred except
where explicitly excluded. In all other cases, no attributes are assumed
except where explicitly included.

Destination attributes are interpolated from the source attributes using a
weighted proximity technique. Proximities used in point attribute calculations
are determined as the distance between the destination point and the candidate
source points. For primitive attribute calculations, the
barycenter-to-barycenter distance between the destination primitive and the
candidate source primitives is used. In the case of vertex attributes, each
destination vertex is first mapped to the closest position and primitive in the
source geometry. The vertex attribute is then determined using a
barycentric-like interpolation technique. The source detail attribute is simply
copied to the destination detail attribute.

The "Conditions" folder contains several parameters that control how the
source attributes are combined, or filtered, to give the resulting destination
values. The "Kernel Function" can be set to any available metaball kernel. The
kernels are parameterized by distance and typically give more weight to
source points/primitives/vertices that are closer. The "Max Sample Count"
parameter specifies the maximum number of points/primitives/vertices to
interpolate from. A maximum sample count of 1 gives nearest neighbour
interpolation. The "Kernel Radius" specifies the drop-off radius for the kernel
function. As the kernel radius parameter approaches zero, the filter resembles
nearest neighbour interpolation. As the kernel radius parameter increases, the
filter approaches uniform weighting. The "Distance Threshold" parameter
specifies the maximum distance source points/primitives must be to be
considered. Switching off this option indicates that no points/primitives will
be excluded based on distance. Within the distance threshold, the final
attributes are determined solely from the source selection. In cases where all
source points/primitives/vertices lie beyond the distance threshold, the
destination attributes remain unchanged. The "Blend Width" parameter relaxes
the distance threshold and optionally sets a region outside the distance
threshold where the influence of the source attributes gradually tapers off.
In this region, the interpolated source attribute value is blended with the
original destination attribute value using the selected kernel function to
produce the interpolation factors. In this blending process, the blend width
is used as the kernel radius. The "Uniform Bias" parameter specifies the linear
interpolation factor that is used when blending with the Uniform kernel
function. The Uniform Bias value is used as the source blending factor, whereas
the destination blending factor is set to one minus this value.

Parameters:
    Source Group		- A subset of the source geometry where
				  attribute values are transferred from.
    Source Group Type		- The type of elements referenced in the Source
				  Group field.
    Destination Group		- A subset of the destination geometry where
				  attribute values are transferred to.
    Destination Group Type	- The type of elements referenced in the
				  Destination Group field.
    Detail			- Source detail attributes to transfer.
    Primitives			- Source primitive attributes to transfer.
    Points			- Source point attributes to transfer.
    Vertices			- Source vertex attributes to transfer.
    Kernel Function		- Interpolating metaball kernel.
    Max Sample Count		- Number of closest samples to interpolate from.
    Kernel Radius		- Radial extent of the kernel function.
    Distance Threshold		- Radial extent of the filter domain where the
				  final attributes are determined from the
				  source selection only.
    Blend Width			- The radial extent beyond the distance
				  threshold where the final attributes are
				  blended from the source and destination
				  selections using the Kernel Function and the
				  Blend Width as the kernel radius. In regions
				  outside the Distance Threshold + Blend Width,
				  the destination attributes remain unchanged.
    Uniform Bias		- The linear interpolation factor that is used
				  when blending with the Uniform kernel
				  function. This value is used for the source,
				  whereas the destination factor is set to
				  '1 - Uniform Bias'.

See also: Attribute, AttribCopy, AttribCreate, Point, Primitive, Vertex, GroupTransfer
