System to inspect `PhysicsJoint` and `PhysicsConstrainedBodyPair` data

.PhysicsJointDebugSystem.cs.md

System to visually inspect PhysicsJoint and PhysicsConstrainedBodyPair data

Written for entities 1.0.16, physics 1.0.16

PhysicsJointDebugSystem.cs

// src* https://gist.github.com/andrew-raphael-lukasik/aa88cf6f32634126849dfe176f11a955
using UnityEngine;
using Unity.Entities;
using Unity.Collections;
using Unity.Mathematics;
using Unity.Transforms;
using Unity.Physics;
using Unity.Physics.Extensions;
using Unity.Physics.Systems;
using Unity.Jobs;

namespace EditorOnly.Authoring
{
    [Unity.Burst.BurstCompile]
    [RequireMatchingQueriesForUpdate]
    [WorldSystemFilter( WorldSystemFilterFlags.Default | WorldSystemFilterFlags.Editor )]
    [UpdateInGroup( typeof(Unity.Physics.Authoring.PhysicsDisplayDebugGroup) )]
    public partial struct PhysicsJointDebugSystem : ISystem
    {
        ComponentLookup<LocalToWorld> _lookupLTW;

        [Unity.Burst.BurstCompile]
        public void OnCreate ( ref SystemState state )
        {
            _lookupLTW = state.GetComponentLookup<LocalToWorld>( isReadOnly:true );
            state.RequireForUpdate<SystemStartRequest>();
        }

        [Unity.Burst.BurstCompile]
        public void OnDestroy ( ref SystemState state ) {}

        [Unity.Burst.BurstCompile]
        public void OnUpdate ( ref SystemState state )
        {
            _lookupLTW.Update( ref state );
            state.EntityManager.CompleteDependencyBeforeRO<LocalToWorld>();
            foreach( var( pj , pcb ) in SystemAPI.Query< RefRO<PhysicsJoint> , RefRO<PhysicsConstrainedBodyPair> >() )
            {
                Entity entityA = pcb.ValueRO.EntityA;
                Entity entityB = pcb.ValueRO.EntityB;

                var ltwA = _lookupLTW[entityA];
                var ltwB = _lookupLTW[entityB];

                var bodyAFromJoint = pj.ValueRO.BodyAFromJoint;
                var bodyBFromJoint = pj.ValueRO.BodyBFromJoint;

                Debug.DrawLine( ltwA.Position , ltwA.Value.TransformPoint(bodyAFromJoint.Position) , Color.cyan );
                Debug.DrawRay( ltwA.Position , ltwA.Value.TransformDirection(bodyAFromJoint.Axis) , Color.red );
                Debug.DrawRay( ltwA.Position , ltwA.Value.TransformDirection(bodyAFromJoint.PerpendicularAxis) , Color.green );

                Debug.DrawLine( ltwB.Position , ltwB.Value.TransformPoint(bodyBFromJoint.Position) , Color.yellow );
                Debug.DrawLine( ltwB.Position , ltwB.Value.TransformPoint(bodyBFromJoint.Axis) , Color.red );
                Debug.DrawLine( ltwB.Position , ltwB.Value.TransformPoint(bodyBFromJoint.PerpendicularAxis) , Color.green );
            }
        }

        public struct SystemStartRequest : IComponentData {}

    }
}