A paintable attribute is a node attribute that has been registered as paintable through the makePaintable command in Maya. When you register an attribute, it is stored in your user preferences and stays paintable between Maya sessions, and between each separate use of the Paint Attributes Tool. You only need to register an attribute as paintable once. After an attribute is made paintable, the Paint Attributes Tool automatically finds it on the selected surface.
Painting attributes should be added to the shape node (pPlaneShape1), not the transform node (pPlane1).
// Add an attribute to paint select pPlaneShape1; addAttr -ln "paintAttr" -dataType "doubleArray";
// Make it paintable makePaintable "mesh" "paintAttr";
Register a paintable attribute
Use the following command to register an attribute as paintable:
makePaintable [flags] <nodeType> <attrName>
This flag defines a function which is called when the matching between the paintable node depends on the painted shape. It is used for attributes of type multi where the first multi corresponds to the shape index (for example, cluster nodes). Currently only one function is supported: deformer. By default this flag is empty, which means that there is a direct indexing of the paintable attribute with respect to vertices on the shape.
makePaintable -attrType "doubleArray" "particle" "mass";
makePaintable -ui "myGoalPP" -altAttribute "goalPP0" -attrType "doubleArray" "particle" "goalPP";
makePaintable -sm "deformer" "weightGeometryFilter" "weights";