（十）UI Mesh
1.概述
在unity 网格系列的最后来处理一下UGUI的mesh问题。ugui所有的网格mesh默认为四边形，边长为1，即mesh顶点坐标为四个。由于所有的ui均从Graphic类衍生，所以只要重写虚方法OnPopulateMesh即可。OnPopulateMesh存在两个，入口参数不同，一个时VertexHelper一个时Mesh。入口参数为Mesh的方法已经过失，所以本文主讲VertexHelper生成mesh的方法。如下所示：
protected override void OnPopulateMesh(VertexHelper vh)
{
base.OnPopulateMesh(vh);
vh.Clear();
vh.AddVert(new Vector3(-50,-50), Color.white, new Vector2(0, 0));
vh.AddVert(new Vector3(50, -50), Color.red, new Vector2(1, 0));
vh.AddVert(new Vector3(50, 50), Color.red, new Vector2(1, 1));
vh.AddVert(new Vector3(-50, 50), Color.white, new Vector2(0, 1));
vh.AddTriangle(0, 1, 2);
vh.AddTriangle(0, 2, 3);
}
2.UI Mesh
2.1 操作步骤
新建canvas，并在canvas下新建空的游戏物体，新建一个继承自Graphic脚本并挂载在其上。然后就可以重写OnPopulateMesh方法，并自定义网格。比如可以自定义圆形或者圆环，或者采用ui进行函数曲线的绘制等。
**注意：**在进行网格顶点计算时，要考虑ui的大小，比如概述中顶点坐标对应游戏物体大小为100*100，也可以使用方法GetPixelAdjustedRect()来获取像素大小。
3.2 VertexHelper添加顶点
3.2.1 普通方法
普通方法如概述所示，只要定义顶点，每个顶点的颜色、uv以及三角形即可。颜色可以默认为白色。
3.2.2 顶点编辑
如果要编辑某个顶点信息可以采用PopulateUIVertex方法获取到某个顶点，然后采用SetUIVertex方法重新设置顶点属性。
void CreateMeshRegular(VertexHelper vh)
{
Rect size = GetPixelAdjustedRect();
vh.AddVert(new Vector3(-0.5f * size.width, -0.5f * size.height), Color.white, new Vector2(0, 0));
vh.AddVert(new Vector3(0.5f * size.width, -0.5f * size.height), Color.red, new Vector2(1, 0));
vh.AddVert(new Vector3(0.5f * size.width, 0.5f * size.height), Color.red, new Vector2(1, 1));
vh.AddVert(new Vector3(-0.5f * size.width, 0.5f * size.height), Color.white, new Vector2(0, 1));
vh.AddTriangle(0, 1, 2);
vh.AddTriangle(0, 2, 3);
UIVertex selectedUIVertex = new UIVertex();
vh.PopulateUIVertex(ref selectedUIVertex, 2);
selectedUIVertex.color = Color.green;
vh.SetUIVertex(selectedUIVertex, 2);
}
3.2.3 顶点流方法
顶点流方法是指采用AddUIVertexStream，通过顶点以及三角形的list添加mesh 的方法，如下所示：
void CreateMeshByVertexStream(VertexHelper vh)
{
Rect size = GetPixelAdjustedRect();
UIVertex vertices0 = new UIVertex();
vertices0.position = new Vector3(-0.5f * size.width, -0.5f * size.height);
vertices0.color = Color.blue;
vertices0.uv0 = new Vector2(0, 0);
UIVertex vertices1 = new UIVertex();
vertices1.position = new Vector3(0.5f * size.width, -0.5f * size.height);
vertices1.color = Color.red;
vertices1.uv0 = new Vector2(1, 0);
UIVertex vertices2 = new UIVertex();
vertices2.position = new Vector3(0.5f * size.width, 0.5f * size.height);
vertices2.color = Color.red;
vertices2.uv0 = new Vector2(1, 1);
UIVertex vertices3 = new UIVertex();
vertices3.position = new Vector3(-0.5f * size.width, 0.5f * size.height);
vertices3.color = Color.white;
vertices3.uv0 = new Vector2(0, 1);
List<UIVertex> vertices = new List<UIVertex>()
{
vertices0,vertices1,vertices2,vertices3
};
List<int> triangles = new List<int>()
{
0,1,2,0,2,3
};
vh.AddUIVertexStream(vertices, triangles);
}
3.2.4 添加quad
通过AddUIVertexQuad方法添加四边形，我们只要定义四边形的四个顶点信息，不用定义三角形即可。如下
void CreateMeshByQuad(VertexHelper vh)
{
Rect size = GetPixelAdjustedRect();
UIVertex[] vertices0= new UIVertex[4];
vertices0[0].position = new Vector3(-0.5f * size.width, -0.5f * size.height);
vertices0[0].color = Color.white;
vertices0[0].uv0 = new Vector2(0, 0);
vertices0[1].position = new Vector3(0.5f * size.width, -0.5f * size.height);
vertices0[1].color = Color.red;
vertices0[1].uv0 = new Vector2(1, 0);
vertices0[2].position = new Vector3(0.5f * size.width, 0.5f * size.height);
vertices0[2].color = Color.red;
vertices0[2].uv0 = new Vector2(1, 1);
vertices0[3].position = new Vector3(-0.5f * size.width, 0.5f * size.height);
vertices0[3].color = Color.white;
vertices0[3].uv0 = new Vector2(0, 1);
UIVertex[] vertices1 = new UIVertex[4];
vertices1[0].position = new Vector3(-0.5f * size.width, 0.5f * size.height);
vertices1[0].color = Color.white;
vertices1[0].uv0 = new Vector2(0, 0);
vertices1[1].position = new Vector3(0.5f * size.width, 0.5f * size.height);
vertices1[1].color = Color