Unity 使用SpriteShape製作2D遊戲任意形狀地形

一. 安裝SpriteShape

打開Unity菜單Window-Package Manager

因爲我用的Unity版本是2019.2.14f1，2D SpriteShape插件還屬於preview階段，所以我要打開Show preview packages，
搜索spriteshape即可看到插件，點擊install即可。

安裝後，還可以導入工程例子和拓展資源

二. 創建Sprite Shape Profile

Sprite Shape Profile是用於配置特定形狀類型的所有選項的資源。 通過它我們可以分配要使用的精靈，並告訴Sprite Shape如何渲染它們。
在Project新建一個目錄SpriteShapeRes，然後在這個目錄上右鍵菜單Create-Sprite Shape Profile。
可以看到有兩個子菜單：Open Shape和Closed Shape。

這兩個看名字就可以理解了，如下圖：

比如這裏創建一個Open Shape的profile文件

爲其添加一個精靈圖

三. 製作一個Open Shape地形

在場景中創建一個空物體

給這個物體添加Sprite Shape Controller組件

賦值Profile屬性

此時即可看到場景中出現了一個閉合的形狀

把Is Open Ended勾選上，就不是閉環的了

四. 編輯地形

點擊形狀編輯按鈕，即可在場景中對形狀進行編輯


這裏我們發現路徑是一段一段的，我們想要銜接處是那種圓滑過渡，只需把每個點的Tangent Mode改成Continuous即可


這時發現銜接是圓滑的，但是圖片是斷開的，這是因爲我們沒有設置border。
選中精靈圖，點擊Sprite Editor

設置左右兩邊的border，最後點擊Apply

此時場景中的就得到了我們想要的效果了

五. 添加地形碰撞

想要角色可以在地形上行走，我們還要給地形添加碰撞。
添加Polygon Collider 2D、Composite Collider 2D
此時看到的碰撞是這樣的

再掛上Geometry Collider腳本（這個腳本是上面Extras工具包中的，代碼見文章末尾），然後勾選一下Update Collider


很接近我們想要的效果了，此時再勾選Composite Collider 2D的Used By Effector和Polygon Collider 2D的Used By Composite即可

看到了我們想要的效果

還可以調節Offset，可以調整碰撞的整體偏移，

六. Geometry Collider代碼

using System.Collections;
using System.Collections.Generic;
using Unity.Collections;
using UnityEngine;
using UnityEngine.Experimental.U2D;
using UnityEngine.U2D;

#if UNITY_EDITOR
using UnityEditor;
#endif

[ExecuteAlways]
public class GeometryCollider : MonoBehaviour
{
    [SerializeField]
    bool m_UpdateCollider = false;

    int m_HashCode = 0;

    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        if (m_UpdateCollider)
            Bake(gameObject, false);
    }

    static public void Bake(GameObject go, bool forced)
    {
        var spriteShapeController = go.GetComponent<SpriteShapeController>();
        var spriteShapeRenderer = go.GetComponent<SpriteShapeRenderer>();
        var polyCollider = go.GetComponent<PolygonCollider2D>();
        var geometryCollider = go.GetComponent<GeometryCollider>();

        if (spriteShapeController != null && polyCollider != null)
        {
            var spline = spriteShapeController.spline;
            if (geometryCollider != null)
            { 
                int splineHashCode = spline.GetHashCode();
                if (splineHashCode == geometryCollider.m_HashCode && !forced)
                    return;
                geometryCollider.m_HashCode = splineHashCode;
            }
            NativeArray<ushort> indexArray;
            NativeSlice<Vector3> posArray;
            NativeSlice<Vector2> uv0Array;
            NativeArray<SpriteShapeSegment> geomArray;
            spriteShapeRenderer.GetChannels(65536, out indexArray, out posArray, out uv0Array);
            geomArray = spriteShapeRenderer.GetSegments(spline.GetPointCount() * 8);

            NativeArray<ushort> indexArrayLocal = new NativeArray<ushort>(indexArray.Length, Allocator.Temp);

            List<Vector2> points = new List<Vector2>();
            int indexCount = 0, vertexCount = 0, counter = 0;
            for (int u = 0; u < geomArray.Length; ++u)
            {
                if (geomArray[u].indexCount > 0)
                {
                    for (int i = 0; i < geomArray[u].indexCount; ++i)
                    {
                        indexArrayLocal[counter] = (ushort)(indexArray[counter] + vertexCount);
                        counter++;
                    }
                    vertexCount += geomArray[u].vertexCount;
                    indexCount += geomArray[u].indexCount;
                }
            }
            Debug.Log(go.name + " : " + counter);
            OuterEdges(polyCollider, indexArrayLocal, posArray, indexCount);
        }
    }

    // Generate the outer edges from the Renderer mesh. Based on code from www.h3xed.com
    static void OuterEdges(PolygonCollider2D polygonCollider, NativeArray<ushort> triangles, NativeSlice<Vector3> vertices, int triangleCount)
    {
        // Get just the outer edges from the mesh's triangles (ignore or remove any shared edges)
        Dictionary<string, KeyValuePair<int, int>> edges = new Dictionary<string, KeyValuePair<int, int>>();
        for (int i = 0; i < triangleCount; i += 3)
        {
            for (int e = 0; e < 3; e++)
            {
                int vert1 = triangles[i + e];
                int vert2 = triangles[i + e + 1 > i + 2 ? i : i + e + 1];
                string edge = Mathf.Min(vert1, vert2) + ":" + Mathf.Max(vert1, vert2);
                if (edges.ContainsKey(edge))
                {
                    edges.Remove(edge);
                }
                else
                {
                    edges.Add(edge, new KeyValuePair<int, int>(vert1, vert2));
                }
            }
        }

        // Create edge lookup (Key is first vertex, Value is second vertex, of each edge)
        Dictionary<int, int> lookup = new Dictionary<int, int>();
        foreach (KeyValuePair<int, int> edge in edges.Values)
        {
            if (lookup.ContainsKey(edge.Key) == false)
            {
                lookup.Add(edge.Key, edge.Value);
            }
        }

        // Create empty polygon collider
        polygonCollider.pathCount = 0;

        // Loop through edge vertices in order
        int startVert = 0;
        int nextVert = startVert;
        int highestVert = startVert;
        List<Vector2> colliderPath = new List<Vector2>();
        while (true)
        {

            // Add vertex to collider path
            colliderPath.Add(vertices[nextVert]);

            // Get next vertex
            nextVert = lookup[nextVert];

            // Store highest vertex (to know what shape to move to next)
            if (nextVert > highestVert)
            {
                highestVert = nextVert;
            }

            // Shape complete
            if (nextVert == startVert)
            {

                // Add path to polygon collider
                polygonCollider.pathCount++;
                polygonCollider.SetPath(polygonCollider.pathCount - 1, colliderPath.ToArray());
                colliderPath.Clear();

                // Go to next shape if one exists
                if (lookup.ContainsKey(highestVert + 1))
                {

                    // Set starting and next vertices
                    startVert = highestVert + 1;
                    nextVert = startVert;

                    // Continue to next loop
                    continue;
                }

                // No more verts
                break;
            }
        }
    }

#if UNITY_EDITOR

    [MenuItem("SpriteShape/Generate Geometry Collider", false, 358)]
    public static void BakeGeometryCollider()
    {
        if (Selection.activeGameObject != null)
            GeometryCollider.Bake(Selection.activeGameObject, true);
    }

#endif
}