SplineEditor https://www.assetstore.unity3d.com/jp/#!/content/58080 のスプラインを実線にするようなやつ

MyLineRenderer.cs

using Battlehub.SplineEditor;
using UnityEngine;

[ExecuteInEditMode]
[RequireComponent(typeof(MeshRenderer), typeof(MeshFilter), typeof(MeshCollider))]
public class MyLineRenderer : MonoBehaviour
{
    [SerializeField]
    public Material material;
    [SerializeField]
    public Spline spline;
    [SerializeField, Range(0.1f, 100f)]
    public float segmentPerUnit = 10;
    [SerializeField, Range(0, 1)]
    public float segmentStartT;
    [SerializeField, Range(0, 1)]
    public float width;

    int currentSegmentCount;

    Mesh mesh;
    MeshFilter filter;
    MeshRenderer meshRenderer;

    Vector3[] vertices;
    Vector2[] uvs;
    int[] triangles;

    void Awake()
    {
        filter = GetComponent<MeshFilter>();
        meshRenderer = GetComponent<MeshRenderer>();
        meshRenderer.material = material;

        mesh = new Mesh();
        mesh.hideFlags = HideFlags.DontSave;
        filter.mesh = mesh;

        GetComponent<MeshCollider>().sharedMesh = mesh;

        InitializeVertices(CalculateSegmentCount());
        UpdateMesh();
    }

    void Update()
    {
        if (!Application.isPlaying)
        {
            // セグメント数が変わったら作り直す
            var newSegmentcount = CalculateSegmentCount();
            if (newSegmentcount != currentSegmentCount)
            {
                InitializeVertices(newSegmentcount);
            }
        }

        UpdateMesh();
    }

    int CalculateSegmentCount()
    {
        return Mathf.Max(1, (int)(segmentPerUnit * spline.EvalSplineLength()));
    }

    void InitializeVertices(int segmentCount)
    {
        currentSegmentCount = segmentCount;

        vertices = new Vector3[(segmentCount + 1) * 2];
        uvs = new Vector2[(segmentCount + 1) * 2];
        triangles = new int[segmentCount * 2 * 3];
    }

    void UpdateMesh()
    {
        for (var i = 0; i <= currentSegmentCount; i++) // 普通のループよりひとつおおく
        {
            var t = (float)i / currentSegmentCount;
            var lerpedT = Mathf.Lerp(segmentStartT, 1, t);
            var pos = spline.GetPoint(lerpedT);
            var dir = spline.GetDirection(lerpedT);

            var vertexStart = i * 2;

            // SplineBase の DrawTwistAngle() から借りてきた
            Vector3 v3;
            if (Mathf.Abs(Vector3.Dot(dir, Vector3.up)) < 1.0f)
            {
                v3 = Vector3.Cross(dir, Vector3.up).normalized;
            }
            else
            {
                v3 = Vector3.Cross(dir, Vector3.forward).normalized;
            }

            vertices[vertexStart + 0] = transform.InverseTransformPoint(pos + Quaternion.AngleAxis(spline.GetTwist(lerpedT), dir) * Quaternion.LookRotation(v3, Vector3.up) * Vector3.forward * (width / 2));
            vertices[vertexStart + 1] = transform.InverseTransformPoint(pos - Quaternion.AngleAxis(spline.GetTwist(lerpedT), dir) * Quaternion.LookRotation(v3, Vector3.up) * Vector3.forward * (width / 2));

            uvs[vertexStart + 0] = uvs[vertexStart + 1] = Vector2.one * i;

            if (i != currentSegmentCount) // 最後は面がない
            {
                var faceStart = i * 2 * 3;

                triangles[faceStart + 0] = vertexStart + 0;
                triangles[faceStart + 1] = vertexStart + 1;
                triangles[faceStart + 2] = vertexStart + 2;
                triangles[faceStart + 3] = vertexStart + 2;
                triangles[faceStart + 4] = vertexStart + 1;
                triangles[faceStart + 5] = vertexStart + 3;
            }
        }

        mesh.Clear();

        mesh.vertices = vertices;
        mesh.uv = uvs;
        mesh.triangles = triangles;

        mesh.RecalculateNormals();
        mesh.RecalculateBounds();
    }
}

SplineFollowingObject.cs

using UnityEngine;

[ExecuteInEditMode]
public class SplineFollowingObject : MonoBehaviour
{
    [SerializeField]
    MyLineRenderer myLineRenderer;

    void Update()
    {
        transform.position = myLineRenderer.spline.GetPoint(myLineRenderer.segmentStartT);

        var dir = myLineRenderer.spline.GetDirection(myLineRenderer.segmentStartT);

        // SplineBase の DrawTwistAngle() から借りてきた
        Vector3 v3;
        if (Mathf.Abs(Vector3.Dot(dir, Vector3.up)) < 1.0f)
        {
            v3 = Vector3.Cross(dir, Vector3.up).normalized;
        }
        else
        {
            v3 = Vector3.Cross(dir, Vector3.forward).normalized;
        }

        var twist = myLineRenderer.spline.GetTwist(myLineRenderer.segmentStartT);
        transform.LookAt(transform.position + dir, Quaternion.AngleAxis(twist, dir) * Quaternion.LookRotation(v3, Vector3.up) * Vector3.right);
    }
}