RigidbodyExtensions.cs

using System.Collections.Generic;
using UnityEngine;

namespace OhiraKyou.Extensions {

	public static class RigidbodyExtensions {

		private static Dictionary<Rigidbody, Vector3[]> velocities = new Dictionary<Rigidbody, Vector3[]>();

		private const int VELOCITY_INDEX = 0;
		private const int ANGULAR_VELOCITY_INDEX = 1;


		public static void Pause (this Rigidbody rb) {
			RemoveNullVelocities();

			// Assign velocities to rigidbody's current velocities
			Vector3[] newVelocities = new Vector3[2];
			newVelocities[VELOCITY_INDEX] = rb.velocity;
			newVelocities[ANGULAR_VELOCITY_INDEX] = rb.angularVelocity;

			if (velocities.ContainsKey(rb)) {
				velocities[rb] = newVelocities;
			} else {
				velocities.Add(rb, newVelocities);
			}

			// Freeze rigidbody last to ensure velocities get saved properly
			rb.isKinematic = true;
		}

		public static void UnPause (this Rigidbody rb) {
			RemoveNullVelocities();

			// Unfreeze rigidbody first to ensure the velocity application works
			rb.isKinematic = false;

			// Return velocities to their pre-frozen values)
			Vector3[] associatedVelocities;

			if (velocities.TryGetValue(rb, out associatedVelocities)) {
				rb.velocity = associatedVelocities[VELOCITY_INDEX];
				rb.angularVelocity = associatedVelocities[ANGULAR_VELOCITY_INDEX];

				// Definition has served its temporary purpose; remove it
				velocities.Remove(rb);
			}
		}

		public static void ClearVelocity (this Rigidbody rb) {
			rb.velocity = Vector3.zero;
			rb.angularVelocity = Vector3.zero;
		}


		private static void RemoveNullVelocities () {
			velocities = velocities.WithoutNullKeys<Rigidbody, Vector3[]>();
		}

	}

}