SKConstraint
A specification for constraining a node’s position or rotation.
Declaration
class SKConstraintMentioned in
Overview
An SKConstraint object describes a mathematical constraint on a node’s position or orientation. You attach constraints to nodes; after a scene processes any actions and physics interactions, it applies constraints attached to nodes in its node tree. Use constraints to ensure that certain relationships are true before the system renders a scene. For example, you might use a constraint to:
Change a node’s zRotation property so that it always points at another node or a position in the scene.
Keep a node within a specified distance of another node or a point in the scene.
Keep a node inside a specified rectangle.
Restrict the zRotation property of a node so that it has a more limited rotation range of motion.
To use constraints, create an NSArray object that contains one or more constraint objects and assign the array to a node’s constraints property. When the system evaluates a scene, it executes the constraints on a node in the order they appear in the constraints array.
You can’t change a constraint after you create it. However, you can selectively disable or enable a constraint by setting its enabled property. You can also use the referenceNode property to convert positions to the referenced coordinate system before applying the constraint.