I'm using Godot with Rapier physics engine.
Are Spine2D physics simulated at game runtime, or are the physics animations baked down prior to engine use? If simulated during runtime, does it simulate using Spine2D physics or Rapier physics?
Will a rope with a Spine2D physics constraint interact with a box using Rapier physics?
Spine2D physics animations are not directly integrated with game engine physics like Rapier in Godot. Spine animations, including any physics simulations done within Spine, are calculated dynamically at runtime but do not interact with the game engine's physics system. This means that a rope with a Spine physics constraint will not interact with a box using Rapier physics in Godot. The physics simulations in Spine are used to create animations that are then played back in the game engine, but they do not dynamically interact with the game engine's physics system.
To add to Spinebot's answer, Spine doesn't provide a complete physics engine with collision and other advanced feature, it provides only lightweight physics needed for animations.
If you want your Spine skeleton to affect your game toolkit physics, you can have a game toolkit physics body follow a Spine bone.
Or to go the other way, you can update a Spine bone using your game toolkit's physics body. This can be used to ragdoll your Spine skeleton or have skeleton parts respond to game physics.
