com.unity.ml-agents.tests/Tests/Runtime/Sensor/RigidBodySensorTests.cs

using UnityEngine;
using NUnit.Framework;
using Unity.MLAgents.Sensors;

namespace Unity.MLAgents.Tests
{
    public class RigidBodySensorTests
    {
        [Test]
        public void TestNullRootBody()
        {
            var gameObj = new GameObject();

            var sensorComponent = gameObj.AddComponent<RigidBodySensorComponent>();
            Assert.IsFalse(sensorComponent.IsTrivial());
            var sensor = sensorComponent.CreateSensors()[0];
            SensorTestHelper.CompareObservation(sensor, new float[0]);
        }

        [Test]
        public void TestSingleRigidbody()
        {
            var gameObj = new GameObject();
            var rootRb = gameObj.AddComponent<Rigidbody>();
            var sensorComponent = gameObj.AddComponent<RigidBodySensorComponent>();
            sensorComponent.RootBody = rootRb;
            sensorComponent.Settings = new PhysicsSensorSettings
            {
                UseModelSpaceLinearVelocity = true,
                UseLocalSpaceTranslations = true,
                UseLocalSpaceRotations = true
            };
            Assert.IsTrue(sensorComponent.IsTrivial());

            var sensor = sensorComponent.CreateSensors()[0];
            sensor.Update();

            // The root body is ignored since it always generates identity values
            // and there are no other bodies to generate observations.
            var expected = new float[0];
            Assert.AreEqual(expected.Length, sensor.GetObservationSpec().Shape[0]);
            SensorTestHelper.CompareObservation(sensor, expected);
        }

        // TODO: figure out why this fails with position mismatches when upgrading from
        // Unity 2022.3 to Unity 2023.2.
#if !UNITY_2023_2_OR_NEWER
        [Test]
        public void TestBodiesWithJoint()
        {
            var rootObj = new GameObject();
            var rootRb = rootObj.AddComponent<Rigidbody>();
            rootRb.velocity = new Vector3(1f, 0f, 0f);

            var middleGamObj = new GameObject();
            var middleRb = middleGamObj.AddComponent<Rigidbody>();
            middleRb.velocity = new Vector3(0f, 1f, 0f);
            middleGamObj.transform.SetParent(rootObj.transform);
            middleGamObj.transform.localPosition = new Vector3(13.37f, 0f, 0f);
            var joint = middleGamObj.AddComponent<ConfigurableJoint>();
            joint.connectedBody = rootRb;

            var leafGameObj = new GameObject();
            var leafRb = leafGameObj.AddComponent<Rigidbody>();
            leafRb.velocity = new Vector3(0f, 0f, 1f);
            leafGameObj.transform.SetParent(middleGamObj.transform);
            leafGameObj.transform.localPosition = new Vector3(4.2f, 0f, 0f);
            var joint2 = leafGameObj.AddComponent<ConfigurableJoint>();
            joint2.connectedBody = middleRb;

            var virtualRoot = new GameObject();

            var sensorComponent = rootObj.AddComponent<RigidBodySensorComponent>();
            sensorComponent.RootBody = rootRb;
            sensorComponent.Settings = new PhysicsSensorSettings
            {
                UseModelSpaceTranslations = true,
                UseLocalSpaceTranslations = true,
                UseLocalSpaceLinearVelocity = true
            };
            sensorComponent.VirtualRoot = virtualRoot;
            Assert.IsFalse(sensorComponent.IsTrivial());

            var sensor = sensorComponent.CreateSensors()[0];
            sensor.Update();

            // Note that the VirtualRoot is ignored from the observations
            var expected = new[]
            {
                // Model space
                0f, 0f, 0f, // Root pos
                middleGamObj.transform.position.x, 0f, 0f, // Middle pos
                leafGameObj.transform.position.x, 0f, 0f, // Leaf pos

                // Local space
                0f, 0f, 0f, // Root pos
                middleGamObj.transform.localPosition.x, 0f, 0f, // Attached pos
                leafGameObj.transform.localPosition.x, 0f, 0f, // Leaf pos

                1f, 0f, 0f, // Root vel (relative to virtual root)
                -1f, 1f, 0f, // Attached vel
                0f, -1f, 1f // Leaf vel
            };
            Assert.AreEqual(expected.Length, sensor.GetObservationSpec().Shape[0]);
            SensorTestHelper.CompareObservation(sensor, expected);

            // Update the settings to only process joint observations
            sensorComponent.Settings = new PhysicsSensorSettings
            {
                UseJointPositionsAndAngles = true,
                UseJointForces = true,
            };

            sensor = sensorComponent.CreateSensors()[0];
            sensor.Update();

            expected = new[]
            {
                0f, 0f, 0f, // joint1.force
                0f, 0f, 0f, // joint1.torque
                0f, 0f, 0f, // joint2.force
                0f, 0f, 0f, // joint2.torque
            };
            SensorTestHelper.CompareObservation(sensor, expected);
            Assert.AreEqual(expected.Length, sensor.GetObservationSpec().Shape[0]);
        }
#endif
    }
}