前言
最近需要將一個2D網格邊緣上繪製虛線,最初考慮使用渲染的後處理來實現,但是後處理代價大,而且效果也並不理想,於是打算採用LineRenderer來繪製邊緣的虛線。
最後效果如下:
四張圖分別是Quad、Plane、自定義形狀、帶空洞的自定義形狀。
步驟與原理
1、獲取目標網格上的所有頂點、三角面信息。
2、提取出網格上所有三角面的三條邊。
3、比較所邊緣信息,清除重複使用的邊緣。被共用的邊緣是兩個三角面的相交線,如Quad中間的那條對角線。
4、將爲重複的邊緣排序連成線,對有多邊緣的形狀,返回多條線。
5、使用LineRender組件將線繪製出來。
實現
using System.Collections.Generic;
using UnityEngine;
public class MeshVertexLineRenderer : MonoBehaviour
{
public Material material;
public void AddLine()
{
AddLine(GetComponent<MeshFilter>().sharedMesh, transform);
}
public void DeleteLine()
{
DeleteLine(transform);
}
private void AddLine(Mesh mesh, Transform parent)
{
DeleteLine(parent);
Vector3[] meshVertices = mesh.vertices;
List<List<Vector3>> vertices = TrianglesAndVerticesEdge(mesh.vertices, mesh.triangles);
for (int i = 0; i < vertices.Count; i++)
AddSingleLine(i, vertices[i].ToArray(), parent);
}
private void AddSingleLine(int index, Vector3[] vertices, Transform parent)
{
LineRenderer lineRenderer = new GameObject("MeshVertexLine_" + index, new System.Type[] { typeof(LineRenderer) }).GetComponent<LineRenderer>();
lineRenderer.transform.parent = parent;
lineRenderer.transform.localPosition = Vector3.zero;
lineRenderer.transform.localRotation = Quaternion.identity;
lineRenderer.shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;
lineRenderer.receiveShadows = false;
lineRenderer.allowOcclusionWhenDynamic = false;
lineRenderer.motionVectorGenerationMode = MotionVectorGenerationMode.ForceNoMotion;
lineRenderer.useWorldSpace = false;
lineRenderer.loop = true;
lineRenderer.widthMultiplier = 0.1f;
lineRenderer.sortingLayerName = "GamePlay";
lineRenderer.sortingOrder = 501;
lineRenderer.lightProbeUsage = UnityEngine.Rendering.LightProbeUsage.Off;
lineRenderer.reflectionProbeUsage = UnityEngine.Rendering.ReflectionProbeUsage.Off;
lineRenderer.alignment = LineAlignment.View;
lineRenderer.textureMode = LineTextureMode.Tile;
lineRenderer.material = material;
lineRenderer.positionCount = vertices.Length;
lineRenderer.SetPositions(vertices);
}
private void DeleteLine(Transform parent)
{
for (int i = 0; i < parent.childCount; i++)
{
if (parent.GetChild(i).name.Contains("MeshVertexLine"))
{
GameObject gameObject = parent.GetChild(i).gameObject;
if (gameObject != null)
{
i--;
#if UNITY_EDITOR
if (Application.isPlaying)
{
Object.Destroy(gameObject);
}
else
{
Object.DestroyImmediate(gameObject);
}
#else
Object.Destroy(gameObject);
#endif
}
}
}
}
/// <summary>
/// 網格系統邊緣查找,支持多邊緣
/// </summary>
/// <param name="vertices"></param>
/// <param name="triangles"></param>
/// <returns></returns>
private List<List<Vector3>> TrianglesAndVerticesEdge(Vector3[] vertices, int[] triangles)
{
List<Vector2Int> edgeLines = TrianglesEdgeAnalysis(triangles);
List<List<Vector3>> result = SpliteLines(edgeLines, vertices);
return result;
}
/// <summary>
/// 三角面組邊緣提取
/// </summary>
/// <param name="triangles"></param>
/// <param name="edges"></param>
/// <param name="invalidFlag"></param>
/// <returns></returns>
private List<Vector2Int> TrianglesEdgeAnalysis(int[] triangles)
{
int[,] edges = new int[triangles.Length, 2];
for (int i = 0; i < triangles.Length; i += 3)
{
for (int j = 0; j < 3; j++)
{
for (int k = 0; k < 2; k++)
{
int index = (j + k) % 3;
edges[i + j, k] = triangles[i + index];
}
}
}
bool[] invalidFlag = new bool[triangles.Length];
for (int i = 0; i < triangles.Length; i++)
{
for (int j = i + 1; j < triangles.Length; j++)
{
if ((edges[i, 0] == edges[j, 0] && edges[i, 1] == edges[j, 1]) || (edges[i, 0] == edges[j, 1] && edges[i, 1] == edges[j, 0]))
{
invalidFlag[i] = true;
invalidFlag[j] = true;
}
}
}
List<Vector2Int> edgeLines = new List<Vector2Int>();
for (int i = 0; i < triangles.Length; i++)
{
if (!invalidFlag[i])
{
edgeLines.Add(new Vector2Int(edges[i, 0], edges[i, 1]));
}
}
if (edgeLines.Count == 0)
{
Debug.Log("Calculate wrong, there is not any valid line");
}
return edgeLines;
}
/// <summary>
/// 邊緣排序與分離
/// </summary>
/// <param name="edgeLines"></param>
/// <param name="vertices"></param>
/// <returns></returns>
private List<List<Vector3>> SpliteLines(List<Vector2Int> edgeLines, Vector3[] vertices)
{
List<List<Vector3>> result = new List<List<Vector3>>();
List<int> edgeIndex = new List<int>();
int startIndex = edgeLines[0].x;
edgeIndex.Add(edgeLines[0].x);
int removeIndex = 0;
int currentIndex = edgeLines[0].y;
while (true)
{
edgeLines.RemoveAt(removeIndex);
edgeIndex.Add(currentIndex);
bool findNew = false;
for (int i = 0; i < edgeLines.Count && !findNew; i++)
{
if (currentIndex == edgeLines[i].x)
{
currentIndex = edgeLines[i].y;
removeIndex = i;
findNew = true;
}
else if (currentIndex == edgeLines[i].y)
{
currentIndex = edgeLines[i].x;
removeIndex = i;
findNew = true;
}
}
if (findNew && currentIndex == startIndex)
{
Debug.Log("Complete Closed curve");
edgeLines.RemoveAt(removeIndex);
List<Vector3> singleVertices = new List<Vector3>();
for (int i = 0; i < edgeIndex.Count; i++)
singleVertices.Add(vertices[edgeIndex[i]]);
result.Add(singleVertices);
if (edgeLines.Count > 0)
{
edgeIndex = new List<int>();
startIndex = edgeLines[0].x;
edgeIndex.Add(edgeLines[0].x);
removeIndex = 0;
currentIndex = edgeLines[0].y;
}
else
{
break;
}
}
else if (!findNew)
{
Debug.Log("Complete curve, but not closed");
List<Vector3> singleVertices = new List<Vector3>();
for (int i = 0; i < edgeIndex.Count; i++)
singleVertices.Add(vertices[edgeIndex[i]]);
result.Add(singleVertices);
if (edgeLines.Count > 0)
{
edgeIndex = new List<int>();
startIndex = edgeLines[0].x;
edgeIndex.Add(edgeLines[0].x);
removeIndex = 0;
currentIndex = edgeLines[0].y;
}
else
{
break;
}
}
}
return result;
}
}
LineRenderer組件
LineRenderer組件繪製線,會沿着模型點繪製,實際上我們需要線繪製到模型的內側(或者外側)。
在Unity中,從一個方向觀察Mesh的三角面頂點排序爲逆時針時,這個方向看到的就是三角面的正面。
即俯視三角面的Front時,三角面頂點排序爲逆時針;我們最後得到的線爲L,沿着L的方向看,圖形始終在左手邊。
這些調整可以直接在材質中處理: