SplineRoad.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Unity.Mathematics;
using UnityEngine.Splines;

public class SplineRoad : MonoBehaviour
{
    [SerializeField] SplineContainer _spline;
    [SerializeField] Material _mtl;
    [SerializeField] Material _mtlDuraBarrier;
    [SerializeField] float _width = 5f;
    [SerializeField] float _height = 5f;
    [SerializeField] float _divideLength = 1f;
    [SerializeField] float _barrierHeight = 1f;
    [SerializeField] float _barrierWidth = 0.2f;

    Mesh createMesh()
    {
        List<Vector3> points = new List<Vector3>();
        List<Vector2> uvs = new List<Vector2>();
        List<Vector3> normals = new List<Vector3>();
        List<int> triangles = new List<int>();
        int pointOfs = 0;
        foreach(var s in _spline.Splines)
        {
            var length = s.CalculateLength(float4x4.identity);
            int pointCount = 0;
            for (float len = 0f; len < length; len += 1f)
            {
                var t = len / length;
                var pos = (Vector3)s.EvaluatePosition(t);
                var tangent = s.EvaluateTangent(t);
                var up = s.EvaluateUpVector(t);
                var right = Vector3.Cross(tangent, up).normalized;
                points.Add(pos - right * _width * 0.5f);    // left
                points.Add(pos + right * _width * 0.5f);    // right
                uvs.Add(new Vector2(0f,len / _height)); // left
                uvs.Add(new Vector2(1f, len / _height));    // right
                normals.Add(up);    // left
                normals.Add(up);    // right
                ++pointCount;
            }
            for(int i=0;i< pointCount-1;++i)
            {
                triangles.Add((i+ pointOfs) * 2 + 0);   // 0
                triangles.Add((i+ pointOfs) * 2 + 1);   // 1
                triangles.Add((i+ pointOfs) * 2 + 2);   // 2
                triangles.Add((i+ pointOfs) * 2 + 1);   // 1
                triangles.Add((i+ pointOfs) * 2 + 3);   // 3
                triangles.Add((i+ pointOfs) * 2 + 2);   // 2
            }
            pointOfs += pointCount * 2;
        }
        var mesh = new Mesh();
        mesh.SetVertices(points);
        mesh.SetUVs(0, uvs);
        mesh.SetNormals(normals);
        mesh.SetTriangles(triangles,0);
        mesh.RecalculateTangents();
        return mesh;
    }

    Mesh createBarrierMesh()
    {
        List<Vector3> points = new List<Vector3>();
        List<Vector2> uvs = new List<Vector2>();
        List<Vector3> normals = new List<Vector3>();
        List<int> triangles = new List<int>();
        int pointOfs = 0;
        foreach (var s in _spline.Splines)
        {
            var length = s.CalculateLength(float4x4.identity);
            int pointCount = 0;
            for (float len = 0f; len < length; len += 1f)
            {
                var t = len / length;
                var pos = (Vector3)s.EvaluatePosition(t);
                var tangent = s.EvaluateTangent(t);
                var up = (Vector3)s.EvaluateUpVector(t);
                var right = Vector3.Cross(tangent, up).normalized;
                points.Add(pos - right * (_width * 0.5f + _barrierWidth));    // left 0
                points.Add(pos - right * (_width * 0.5f + _barrierWidth) + up * _barrierHeight);    // left 1
                points.Add(pos - right * _width * 0.5f + up * _barrierHeight);    // left 2
                points.Add(pos - right * _width * 0.5f);    // left 3
                points.Add(pos + right * _width * 0.5f);    // right0
                points.Add(pos + right * _width * 0.5f + up * _barrierHeight);    // right1
                points.Add(pos + right * (_width * 0.5f + _barrierWidth) + up * _barrierHeight);    // right2
                points.Add(pos + right * (_width * 0.5f + _barrierWidth));    // right3
                uvs.Add(new Vector2(0f, len / _height)); // left0
                uvs.Add(new Vector2(1f, len / _height)); // left1
                uvs.Add(new Vector2(1f, len / _height)); // left2
                uvs.Add(new Vector2(0f, len / _height)); // left3
                uvs.Add(new Vector2(0f, len / _height));    // right0
                uvs.Add(new Vector2(1f, len / _height));    // right1
                uvs.Add(new Vector2(1f, len / _height));    // right2
                uvs.Add(new Vector2(0f, len / _height));    // right3
                normals.Add(-right);    // left0
                normals.Add(-right);    // left1
                normals.Add(right);    // left2
                normals.Add(right);    // left3
                normals.Add(-right);    // right0
                normals.Add(-right);    // right1
                normals.Add(right);    // right2
                normals.Add(right);    // right3
                ++pointCount;
            }
            const int linePoint = 8;
            const int lineHalf = 4;
            for (int i = 0; i < pointCount - 1; ++i)
            {
                for (int j = 0; j < 3; ++j)
                {
                    triangles.Add((i + pointOfs) * linePoint + 0 + j);   // 0
                    triangles.Add((i + pointOfs) * linePoint + 1 + j);   // 1
                    triangles.Add((i + pointOfs + 1) * linePoint + 0 + j);   // 2
                    triangles.Add((i + pointOfs) * linePoint + 1 + j);   // 1
                    triangles.Add((i + pointOfs + 1) * linePoint + 1 + j);   // 3
                    triangles.Add((i + pointOfs + 1) * linePoint + 0 + j);   // 2
                }
                for (int j = 0; j < 3; ++j)
                {
                    triangles.Add((i + pointOfs) * linePoint + 0+ lineHalf + j);   // 0
                    triangles.Add((i + pointOfs) * linePoint + 1 + lineHalf + j);   // 1
                    triangles.Add((i + pointOfs + 1) * linePoint + 0 + lineHalf + j);   // 2
                    triangles.Add((i + pointOfs) * linePoint + 1 + lineHalf + j);   // 1
                    triangles.Add((i + pointOfs + 1) * linePoint + 1 + lineHalf + j);   // 3
                    triangles.Add((i + pointOfs + 1) * linePoint + 0 + lineHalf + j);   // 2
                }
            }
            pointOfs += pointCount * 2;
        }
        var mesh = new Mesh();
        mesh.SetVertices(points);
        mesh.SetUVs(0, uvs);
        mesh.SetNormals(normals);
        mesh.SetTriangles(triangles, 0);
        mesh.RecalculateTangents();
        return mesh;
    }

    private void OnDestroy()
    {
        var mf = gameObject.GetComponent<MeshFilter>();
        if (mf)
        {
            DestroyImmediate(mf.sharedMesh);
        }
    }

    // Start is called before the first frame update
    void Start()
    {
        {
            var o = new GameObject();
            o.name = "Road";
            o.transform.SetParent(transform, false);
            var mesh = createMesh();
            var mf = o.AddComponent<MeshFilter>();
            mf.sharedMesh = mesh;
            var mr = o.AddComponent<MeshRenderer>();
            mr.sharedMaterial = _mtl;
            var mc = o.AddComponent<MeshCollider>();
            mc.sharedMesh = mesh;
        }
        {
            var o = new GameObject();
            o.name = "Barrier";
            o.transform.SetParent(transform, false);
            var mesh = createBarrierMesh();
            var mf = o.AddComponent<MeshFilter>();
            mf.sharedMesh = mesh;
            var mr = o.AddComponent<MeshRenderer>();
            mr.sharedMaterial = _mtlDuraBarrier;
            var mc = o.AddComponent<MeshCollider>();
            mc.sharedMesh = mesh;
        }
    }

    // Update is called once per frame
    void Update()
    {
        
    }
}