addVisual(body,"Mesh",filename) adds a polygon mesh on top of any current visual geometry using the specified .stl file, filename. Multiple visual geometries can be added to a single body. The coordinate frame is assumed to coincide with the frame of body. You can view the meshes for an entire rigid body tree using show.

addVisual(body,"Mesh",filename,tform) specifies a homogeneous transformation for the polygon mesh relative to the body frame.