A reference to a weight map or other attribute on the emitter to filter locations by. If this option is used, the attribute
is used to control the rate of emission across the geometry.
If the emission type is set to "Surface", you can specify a portion of the surface; if the emission type is set to "Point",
you can specify the points.
The supported types for the attribute are: Boolean, integer and scalar. Integer and scalar values are clamped to a minimum
of 0 and a maximum of 1.
A value of 0 (or false for Boolean) means the corresponding vertex or triangle is discarded from the set of locations. Scalar
values between 0 and 1 are used as weights when the emission type is set to Surface: a triangle will emit N% of the locations
that it would have emitted without filtering where N is equal to the weight of the triangle multiplied by 100.
The current attribute contexts supported when emitting from a surface are:

vertex: the weight of a triangle is the average of the weights of its three vertices.

polygon: the weight of a triangle is the value of the attribute at the center of the triangle.

polynode: the weight of a triangle is the average of the weights of its three polynodes.
