主要写一下OnPopulateMesh函数的使用方式
OnPopulateMesh函数
当一个UI元素生成顶点数据时会调用OnPopulateMesh(VertexHelper vh)函数,我们可以在这个函数中修改顶点的数据或者获取顶点的数据。
VertexHelper结构
UI元素的顶点数据会填充这个数据结构,我们可以修改这个数据结构里面的数据从而影响到顶点的一些属性。
在Unity文档中我们会看到如下的属性和方法,我们会一一介绍这写属性和方法的使用。
AddVert
添加一个顶点到VertexHelper缓存中
AddTriangle
添加一个三角形到VertexHelper缓存中
例子:
我们用AddVert和AddTriangle绘制一个三角形
我们创建一个脚本TestVertexHelper.cs并继承Graphic,因为OnPopulateMesh函数定义在Graphic中
- public class TestVertexHelper : Graphic
- {
-
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
- vh.AddVert(new Vector3(0, 0), Color.red, Vector2.zero);
- vh.AddVert(new Vector3(0, 100), Color.green, Vector2.zero);
- vh.AddVert(new Vector3(100, 100), Color.black, Vector2.zero);
-
- vh.AddTriangle(0, 1, 2);
-
- }
- }
首先我们用AddVert添加了三个顶点,三个顶点的关系如上图,然后用AddTriangle添加三角形,参数是三角形顶点的索引。GPU在绘制的时候会按照顶点0->顶点1->顶点2来绘制一个三角形
我们用AddVert和AddTriangle绘制一个正方形形
- public class TestVertexHelper : Graphic
- {
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
-
- vh.AddVert(new Vector3(0, 0), Color.red, Vector2.zero);
- vh.AddVert(new Vector3(0, 100), Color.green, Vector2.zero);
- vh.AddVert(new Vector3(100, 100), Color.black, Vector2.zero);
- vh.AddVert(new Vector3(100, 0), Color.blue, Vector2.zero);
-
- vh.AddTriangle(0, 1, 2);
- vh.AddTriangle(2, 3, 0);
- }
- }
我们首先用AddVert添加了四个顶点,顶点的顺序如图;然后用AddTriangle添加了两个三角形,其中vh.AddTriangle(0, 1, 2)表示用顶点0,1,2来绘制一个三角形,vh.AddTriangle(2, 3, 0)表示用顶点2,3,0来绘制一个三角形。属性currentIndexCount 和currentVertCount
currentVertCount表示VertexHelper结构中有几个顶点
currentIndexCount表示VertexHelper结构中有几个顶点索引
我们来打印一下刚才绘制的正方形的信息
- public class TestVertexHelper : Graphic
- {
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
-
- vh.AddVert(new Vector3(0, 0), Color.red, Vector2.zero);
- vh.AddVert(new Vector3(0, 100), Color.green, Vector2.zero);
- vh.AddVert(new Vector3(100, 100), Color.black, Vector2.zero);
- vh.AddVert(new Vector3(100, 0), Color.blue, Vector2.zero);
-
- vh.AddTriangle(0, 1, 2);
- vh.AddTriangle(2, 3, 0);
-
- Debug.Log("currentIndexCount " + vh.currentIndexCount);
- Debug.Log("currentVertCount " + vh.currentVertCount);
- }
- }
我们看到顶点索引有四个,顶点有六个
顶点索引有四个(0,1,2,3)这个好理解,但是我们用AddVert添加了四个顶点,这里怎么显示有六个呢?因为unity会把三角形交界处的顶点分成两个。即三角形(0,1,2)和三角形(2,3,0)重合的顶点0,2会被分成两个顶点来处理。
PopulateUIVertex函数
返回指定索引的顶点数据,返回的顶点数据会填充UIVertex数据结构
例子:
我们使用PopulateUIVertex函数获取索引为2的顶点数据,然后打印出来
- public class TestVertexHelper : Graphic
- {
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
-
- vh.AddVert(new Vector3(0, 0), Color.red, Vector2.zero);
- vh.AddVert(new Vector3(0, 100), Color.green, Vector2.zero);
- vh.AddVert(new Vector3(100, 100), Color.black, Vector2.zero);
- vh.AddVert(new Vector3(100, 0), Color.blue, Vector2.zero);
-
- vh.AddTriangle(0, 1, 2);
- vh.AddTriangle(2, 3, 0);
-
- UIVertex vertex = new UIVertex();
- vh.PopulateUIVertex(ref vertex, 2);
- Debug.Log("color " + vertex.color + " position " + vertex.position + " uv0 " + vertex.uv0);
- }
- }
我们看到这个数据,和我们设置的第三个顶点的数据是一样的
SetUIVertex函数
设置一个顶点的数据
我们上面把第三个顶点的颜色设置为了黑色(vh.AddVert(new Vector3(100, 100), Color.black, Vector2.zero);),我们通过SetUIVertex函数把第三个顶点(索引为2的顶点,索引从0开始)的三色设置为黄色
- public class TestVertexHelper : Graphic
- {
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
-
- vh.AddVert(new Vector3(0, 0), Color.red, Vector2.zero);
- vh.AddVert(new Vector3(0, 100), Color.green, Vector2.zero);
- vh.AddVert(new Vector3(100, 100), Color.black, Vector2.zero);
- vh.AddVert(new Vector3(100, 0), Color.blue, Vector2.zero);
-
- vh.AddTriangle(0, 1, 2);
- vh.AddTriangle(2, 3, 0);
-
-
- UIVertex vertex = new UIVertex();
- vh.PopulateUIVertex(ref vertex, 2);
-
- vertex.color = Color.yellow;
- vh.SetUIVertex(vertex, 2);
- }
- }
我们看到索引为2的顶点变成了黄色
AddUIVertexQuad(UIVertex[] verts)函数
增加一个长方形
- public class TestVertexHelper : Graphic
- {
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
- UIVertex[] verts = new UIVertex[4];
- verts[0].position = new Vector3(0, 0);
- verts[0].color = Color.red;
- verts[0].uv0 = Vector2.zero;
-
- verts[1].position = new Vector3(0, 100);
- verts[1].color = Color.green;
- verts[1].uv0 = Vector2.zero;
-
- verts[2].position = new Vector3(100, 100);
- verts[2].color = Color.black;
- verts[2].uv0 = Vector2.zero;
-
- verts[3].position = new Vector3(100, 0);
- verts[3].color = Color.blue;
- verts[3].uv0 = Vector2.zero;
-
- vh.AddUIVertexQuad(verts);
- }
- }
我们看到这个方法和绘制两个三角形产生的效果是一样的
public void AddUIVertexStream(List<UIVertex> verts, List<int> indices);
这个方法向VertexHelper中批量增加顶点数据,第一个参数为顶点数据,第二个参数为构成图元的顶点索引目录
假如我们要绘制两个三角形,加入我们有两个三角形,顶点索引分别为(0,1,2),(2,3,0),那么我们的indices应该定义为
List<int> indices = new List<int>() { 0, 1, 2, 2, 3, 0 };
- public class TestVertexHelper : Graphic
- {
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
- List<UIVertex> verts = new List<UIVertex>();
-
- UIVertex vert0 = new UIVertex();
- vert0.position = new Vector3(0, 0);
- vert0.color = Color.red;
- vert0.uv0 = Vector2.zero;
- verts.Add(vert0);
-
- UIVertex vert1 = new UIVertex();
- vert1.position = new Vector3(0, 100);
- vert1.color = Color.green;
- vert1.uv0 = Vector2.zero;
- verts.Add(vert1);
-
- UIVertex vert2 = new UIVertex();
- vert2.position = new Vector3(100, 100);
- vert2.color = Color.black;
- vert2.uv0 = Vector2.zero;
- verts.Add(vert2);
-
- UIVertex vert3 = new UIVertex();
- vert3.position = new Vector3(100, 0);
- vert3.color = Color.blue;
- vert3.uv0 = Vector2.zero;
- verts.Add(vert3);
-
- List<int> indices = new List<int>() { 0, 1, 2, 2, 3, 0 };
- vh.AddUIVertexStream(verts, indices);
- }
- }
效果:
void AddUIVertexTriangleStream(List<UIVertex> verts)函数
这个方法向VertexHelper中批量增加三角形顶点数据,参数的长度必须是三的倍数
- public class TestVertexHelper : Graphic
- {
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
- List<UIVertex> verts = new List<UIVertex>();
-
- UIVertex vert0 = new UIVertex();
- vert0.position = new Vector3(0, 0);
- vert0.color = Color.red;
- vert0.uv0 = Vector2.zero;
- verts.Add(vert0);
-
- UIVertex vert1 = new UIVertex();
- vert1.position = new Vector3(0, 100);
- vert1.color = Color.green;
- vert1.uv0 = Vector2.zero;
- verts.Add(vert1);
-
- UIVertex vert2 = new UIVertex();
- vert2.position = new Vector3(100, 100);
- vert2.color = Color.black;
- vert2.uv0 = Vector2.zero;
- verts.Add(vert2);
-
- vh.AddUIVertexTriangleStream(verts);
- }
- }
GetUIVertexStream(List<UIVertex> stream)函数
获取当前VertexHelper中的所有顶点的信息
- public class TestVertexHelper : Graphic
- {
-
- protected override void OnPopulateMesh(VertexHelper vh)
- {
- vh.Clear();
-
- vh.AddVert(new Vector3(0, 0), Color.red, Vector2.zero);
- vh.AddVert(new Vector3(0, 100), Color.green, Vector2.zero);
- vh.AddVert(new Vector3(100, 100), Color.black, Vector2.zero);
-
- vh.AddTriangle(0, 1, 2);
-
- List<UIVertex> stream = new List<UIVertex>();
- vh.GetUIVertexStream(stream);
- foreach (UIVertex v in stream) {
- Debug.Log("color " + v.color + " position " + v.position + " uv0 " + v.uv0);
- }
- }
- }
我们看到输出日志的值和我们输入的顶点信息一样