# Morph Constraints

Morph constraint entities restrict the movements of nodes or force compliance with dimensional requirements during morphing. These constraints are always valid for all available morphing approaches.

Morph constraints do not have an active or export state.

## Morph Constraint Types

Fixed
Selected nodes do not move when the mesh morphs around them.
Cluster
Nodes move with the rest of the mesh, but remain fixed relative to each other. The cluster will move, but will also not stretch or become deformed.
Smooth
When handles move on a selected edge domain, the edge morphs according to spline-based motion rather than linear motion, creating smooth edge curves instead of straight edge lines.
You may also choose whether to apply the spline-based motion to the nodes directly, or to dependent handles between the morphed handles.
Along Vector
Nodes will move only in the direction of a selected vector.
Along Line
Nodes will move, but will either move along the length of a selected line or will be bounded by the selected line.
On Plane
Nodes will move, but will either move across the surface of a selected plane, or be bounded by the selected plane.
On Surface
Nodes will move, but will either move across a selected surface, or be bounded by the selected surface.
On Elements
Nodes move, but will either move along the surface of a selected mesh, or be bounded by the selected mesh. This is similar to the along surface option but without requiring surface geometry.
On Equation
Nodes will move, but will either move across the surface of a function, or be bounded by the surface of the function. The surface of a function is defined at the threshold where f(x,y,z) is equal to zero.
Along dofs
Nodes will move, but can have one, two, or all three of their x, y, or z (or r, theta, or phi) coordinates fixed for any given coordinate system, local or global.
Match Elems
Two groups of elements will be forced to match each other regardless of the morphing applied to the nodes on either group. The matching can be forced relative to the normal direction of the elements, relative to a vector, or by selecting nodes to orient one group of elements relative to another.
Note: Three or more groups of elements can be joined together by using this constraint more than once.
Tangency
Continuous tangency can be enforced across a pair of edge or 2D domains. Also, edge domains may have their ends constrained to defined angles, be joined in a main-secondary tangency, or have one edge "attached" to another.
Length
Used in conjunction with one or more morphing shapes, to enforce a specific, maximum, or minimum distance as measured along the nodes in a specified node list.
Angle
Used in conjunction with one or more morphing shapes, to control the angle of three selected nodes. These nodes will move, even relative to each other, but the angle they form remains either fixed, above a certain value, or below a certain value depending on your choice.
Used in conjunction with one or more morphing shapes, to control the radius of a given edge domain.
The radius is measured using an edge domain and one of the following methods for finding the center of curvature: an axis, a line, a node, or inferred from the plane of the edge domain.
For example, if an edge domain lies along a cylinder which has been cut by a plane or planes that are not perpendicular to the axis of the cylinder, the axis of the cylinder can be selected as the center for the radius of the domain. The radius of the domain would then be measured with respect to the assigned axis.
Arc Angle
Used in conjunction with one or more morphing shapes, to control the arc angle of a given edge domain. As for the radius option, the arc angle is measured using an edge domain and one of the following methods for finding the center of curvature: an axis, a line, a node, or inferred from the plane of the edge domain.
Area
Used in conjunction with one or more morphing shapes, to control the area of a number of elements. The selected elements will deform during morphs, but their total surface area remains either constant, above a certain value, or below a certain value, depending in your choice.
Volume
Used in conjunction with one or more morphing shapes, to control the volume of a number of elements. The selected elements will deform during morphs, but the volume of the selected elements remains constant, below a maximum value, or above a minimum value.
Mass
Used in conjunction with density data supplied by a property card, to control the mass of a number of elements. The selected elements will deform during morphs, but the total mass of the selected elements remains equal to, above, or below a specified number, even as the elements change shape during morphing.