SCNLookAtConstraint

For example, you can use a look-at constraint to ensure that a camera or spotlight always follows the movement of a game character. To attach constraints to an SCNNode object, use its constraints property.

A node points in the direction of the negative z-axis of its local coordinate system. This axis defines the view direction for nodes containing cameras and the lighting direction for nodes containing spotlights or directional lights, as well as the orientation of the node’s geometry and child nodes. When Scene Kit evaluates a look-at constraint, it updates the constrained node’s transform property so that the node’s negative z-axis points toward the constraint’s target node.