Constraints
Automatically adjust the position or orientation of a node based on specified rules.
Overview
By modifying the results of animation, physics, and other scene graph changes, constraints make it easier manage dynamic behaviors and relationships between elements of your scene.
For example, when developing a game, you might want a camera node to always point at the player character, even as that character moves around the scene. Instead of directly reorienting the camera node each time you move the character, you can add a look-at constraint to the camera node to make SceneKit reorient the camera automatically.