Understanding the Interaction of Control Planes and Control Points
Control planes (in the Fixed Boundary Plane and Boundary Plane morpher constraint specification methods) work by damping out the displacements smoothly to zero over a specified zone of influence. The RBF morpher requires damping to be applied at these boundaries—for the Fixed Boundary Plane type, the damping applies to displacements in all directions; for the Boundary Plane type, the damping only applies to normal displacements. The BSpline morpher does not require any damping function to be applied.
Control planes extend infinitely in each direction tangential to the plane. The infinite extension means that it is possible to prevent morphing in other parts by setting a plane that intersects the model. The morpher only considers control points above the plane (the outward direction of the surface normal). Any control points on the opposite side of the plane are ignored. The following diagram illustrates such a case.
(This behavior can be avoided by using the Part Surface from the Morpher Constraint Specification or the Boundary Plane with the check box Use Triangulated Plane in Morpher Plane Constraint Specification).
Control Planes for the RBF Morpher
When a mesh vertex is located near or on a control plane, its final displacement due to morphing is calculated by multiplying the predicted displacement from Eqn. (4849) by a damping function. The damping function gives zero displacements (or zero normal displacements for an In Plane type) at the plane, and smooth displacements for points away from the plane. The Damping Factor sets the strength of the damping function. It has units of length, and defines the distance normal to the plane within which damping is applied. As a guide, set the Damping Factor to a length that is about a quarter of the distance from the control plane to other boundaries.
Two damping functions are provided to smooth vertices within the region the Damping Factor defines. These functions are identified in the formulation as C0 continuous, Eqn. (4855), and C2 continuous, [eqnlink]. A plot is given of both functions.
Potential conflicts can occur at the intersection of boundaries that use control plane methods and boundaries that use methods which supply control points. An example would be the intersection of a boundary using the fixed plane method and a boundary using the displacement method. The prescribed displacement could potentially conflict with the fixed plane. For such cases, the morpher can be set to ignore control points that lie within a certain distance from the control plane. The distance is calculated as the Ignore Factor * Damping Factor. Both of these values are given as properties within the Morpher Plane Options boundary value.