ProjectTinySamples/TinyRacing/Assets/Scripts/TinyRacing.Authoring/ControlPointsAuthoring.cs

using Unity.Collections;
using Unity.Entities;
using Unity.Mathematics;
using UnityEngine;

namespace TinyRacing.Authoring
{
    [DisallowMultipleComponent]
    public class ControlPointsAuthoring : MonoBehaviour, IConvertGameObjectToEntity
    {
        public void Convert(Entity entity, EntityManager dstManager, GameObjectConversionSystem conversionSystem)
        {
            dstManager.AddBuffer<ControlPoints>(entity);

            var pointBuffer = dstManager.GetBuffer<ControlPoints>(entity);
            var pointCount = transform.childCount;
            for (int i = 0; i < pointCount; i++)
                pointBuffer.Add(new ControlPoints() { Position = transform.GetChild(i).position });
        }

        // Draw the path between control points
        void OnDrawGizmos()
        {
            var pointCount = transform.childCount;
            for (int i = 0; i < pointCount; i++)
            {
                var previousPosition = (i - 1 < 0) ? transform.GetChild(pointCount - 1).position : transform.GetChild(i - 1).position;
                var startPosition = transform.GetChild(i).position;
                var endPosition = transform.GetChild((i + 1) % pointCount).position;
                var nextPosition = transform.GetChild((i + 2) % pointCount).position;

                var controlPoints = new float3[4] { previousPosition, startPosition, endPosition, nextPosition };

                Gizmos.color = Color.green;
                DrawCurve(controlPoints);
                //DrawNormals(splineSegment);

                Gizmos.color = Color.red;
                Gizmos.DrawWireSphere(startPosition, 0.4f);
            }
        }

        void DrawCurve(float3[] controlPoints)
        {
            var lineCount = 50;
            for (int i = 1; i <= lineCount; i++)
            {
                var previousRatio = (i - 1) / (float)lineCount;
                var ratio = i / (float)lineCount;
                using (NativeArray<float3> points = new NativeArray<float3>(controlPoints, Allocator.Temp))
                {
                    var previousPosition = SplineUtils.GetPoint(points, 0, previousRatio);
                    var currentPosition = SplineUtils.GetPoint(points, 0, ratio);
                    Gizmos.DrawLine(previousPosition, currentPosition);
                }
            }
        }
    }
}