protected override JobHandle OnUpdate(JobHandle inputDeps)
        {
            // EntityCommandBuffer ecb = barrier.CreateCommandBuffer () ;

            EntityArray a_collisionChecksEntities = group.GetEntityArray();

            ComponentDataFromEntity <RayEntityPair4CollisionData> a_rayEntityPair4CollisionData = GetComponentDataFromEntity <RayEntityPair4CollisionData> ();

            ComponentDataFromEntity <IsCollidingData>          a_isCollidingData = GetComponentDataFromEntity <IsCollidingData> ();
            BufferFromEntity <CollisionInstancesBufferElement> collisionInstancesBufferElement = GetBufferFromEntity <CollisionInstancesBufferElement> ();

            ComponentDataFromEntity <RootNodeData> a_octreeRootNodeData = GetComponentDataFromEntity <RootNodeData> ();

            BufferFromEntity <NodeBufferElement> nodeBufferElement = GetBufferFromEntity <NodeBufferElement> ();
            BufferFromEntity <NodeInstancesIndexBufferElement> nodeInstancesIndexBufferElement = GetBufferFromEntity <NodeInstancesIndexBufferElement> ();
            BufferFromEntity <NodeChildrenBufferElement>       nodeChildrenBufferElement       = GetBufferFromEntity <NodeChildrenBufferElement> ();
            BufferFromEntity <InstanceBufferElement>           instanceBufferElement           = GetBufferFromEntity <InstanceBufferElement> ();


            // Ray entity pair, for collision checks

            ComponentDataFromEntity <IsActiveTag> a_isActiveTag = GetComponentDataFromEntity <IsActiveTag> ();

            ComponentDataFromEntity <RayData>            a_rayData            = GetComponentDataFromEntity <RayData> ();
            ComponentDataFromEntity <RayMaxDistanceData> a_rayMaxDistanceData = GetComponentDataFromEntity <RayMaxDistanceData> ();



            // Test ray
            // Debug
            // ! Ensure test this only with single, or at most few ray entiities.
            GetCollidingRayInstances_Common._DebugRays(barrier.CreateCommandBuffer(), a_collisionChecksEntities, a_rayData, a_rayMaxDistanceData, a_isCollidingData, collisionInstancesBufferElement, a_rayEntityPair4CollisionData, false, false);


            // Test ray
            Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);

            // Debug.DrawLine ( ray.origin, ray.origin + ray.direction * 100, Color.red )  ;

            int i_groupLength = group.CalculateLength();


            var setRayTestJob = new SetRayTestJob
            {
                a_collisionChecksEntities     = a_collisionChecksEntities,
                a_rayEntityPair4CollisionData = a_rayEntityPair4CollisionData,

                ray       = ray,
                a_rayData = a_rayData,
                // a_rayMaxDistanceData                = a_rayMaxDistanceData,
            }.Schedule(i_groupLength, 8, inputDeps);



            var job = new Job
            {
                //ecb                                 = ecb,
                a_collisionChecksEntities = a_collisionChecksEntities,

                a_rayEntityPair4CollisionData = a_rayEntityPair4CollisionData,

                a_isCollidingData = a_isCollidingData,
                collisionInstancesBufferElement = collisionInstancesBufferElement,

                a_octreeRootNodeData = a_octreeRootNodeData,

                nodeBufferElement = nodeBufferElement,
                nodeInstancesIndexBufferElement = nodeInstancesIndexBufferElement,
                nodeChildrenBufferElement       = nodeChildrenBufferElement,
                instanceBufferElement           = instanceBufferElement,


                // Ray entity pair, for collision checks

                a_isActiveTag = a_isActiveTag,

                a_rayData            = a_rayData,
                a_rayMaxDistanceData = a_rayMaxDistanceData,
            }.Schedule(i_groupLength, 8, setRayTestJob);

            return(job);
        }
            public void Execute(int i_arrayIndex)
            {
                Entity octreeRootNodeEntity = a_collisionChecksEntities [i_arrayIndex];


                // Its value should be 0, if no collision is detected.
                // And >= 1, if instance collision is detected, or there is more than one collision,
                // indicating number of collisions.
                IsCollidingData isCollidingData = a_isCollidingData [octreeRootNodeEntity];
                // Stores reference to detected colliding instance.
                DynamicBuffer <CollisionInstancesBufferElement> a_collisionInstancesBuffer = collisionInstancesBufferElement [octreeRootNodeEntity];


                isCollidingData.i_nearestInstanceCollisionIndex = 0;
                isCollidingData.f_nearestDistance = float.PositiveInfinity;

                isCollidingData.i_collisionsCount = 0;                // Reset colliding instances counter.


                RootNodeData octreeRootNodeData = a_octreeRootNodeData [octreeRootNodeEntity];

                DynamicBuffer <NodeBufferElement> a_nodesBuffer = nodeBufferElement [octreeRootNodeEntity];
                DynamicBuffer <NodeInstancesIndexBufferElement> a_nodeInstancesIndexBuffer = nodeInstancesIndexBufferElement [octreeRootNodeEntity];
                DynamicBuffer <NodeChildrenBufferElement>       a_nodeChildrenBuffer       = nodeChildrenBufferElement [octreeRootNodeEntity];
                DynamicBuffer <InstanceBufferElement>           a_instanceBuffer           = instanceBufferElement [octreeRootNodeEntity];


                RayEntityPair4CollisionData rayEntityPair4CollisionData = a_rayEntityPair4CollisionData [octreeRootNodeEntity];

                // Ray entity pair, for collision checks

                Entity ray2CheckEntity = rayEntityPair4CollisionData.ray2CheckEntity;

                // Is target octree active
                if (a_isActiveTag.Exists(ray2CheckEntity))
                {
                    RayData            rayData            = a_rayData [ray2CheckEntity];
                    RayMaxDistanceData rayMaxDistanceData = a_rayMaxDistanceData [ray2CheckEntity];


                    // To even allow instances collision checks, octree must have at least one instance.
                    if (octreeRootNodeData.i_totalInstancesCountInTree > 0)
                    {
                        if (GetCollidingRayInstances_Common._GetNodeColliding(octreeRootNodeData, octreeRootNodeData.i_rootNodeIndex, rayData.ray, ref a_collisionInstancesBuffer, ref isCollidingData, a_nodesBuffer, a_nodeChildrenBuffer, a_nodeInstancesIndexBuffer, a_instanceBuffer, rayMaxDistanceData.f))
                        {
                            /*
                             * // Debug
                             * string s_collidingIDs = "" ;
                             * int i_collisionsCount = isCollidingData.i_collisionsCount ;
                             *
                             * for ( int i = 0; i < i_collisionsCount; i ++ )
                             * {
                             *  CollisionInstancesBufferElement collisionInstancesBuffer = a_collisionInstancesBuffer [i] ;
                             *  s_collidingIDs += collisionInstancesBuffer.i_ID + ", " ;
                             * }
                             *
                             * Debug.Log ( "Is colliding with #" + i_collisionsCount + " instances of IDs: " + s_collidingIDs + "; Nearest collided instance is at " + isCollidingData.f_nearestDistance + "m, with index #" + isCollidingData.i_nearestInstanceCollisionIndex ) ;
                             */
                        }
                    }
                }

                a_isCollidingData [octreeRootNodeEntity] = isCollidingData;  // Set back.
            }