用layaAir创建一个扇形mesh

首先需要了解什么是Mesh，在LayaAir中，Mesh是由一系列的顶点和索引组成的三维网格模型，它可以用来创建各种形状的模型。而扇形就是一种简单的形状，可以通过设置顶点和索引的方式来创建。下面是具体实现步骤。

导入LayaAir引擎库，并创建一个Scene场景。

//导入引擎库
import Scene = Laya.Scene;
import MeshSprite3D = Laya.MeshSprite3D;
import Vector3 = Laya.Vector3;
import Sprite3D = Laya.Sprite3D;
import Mesh = Laya.Mesh;
import VertexMesh = Laya.VertexMesh;
import IndexBuffer3D = Laya.IndexBuffer3D;
import VertexBuffer3D = Laya.VertexBuffer3D;

//创建场景
var scene: Scene = Laya.stage.addChild(new Scene()) as Scene;

创建扇形的顶点和索引。

//创建扇形的顶点和索引
var vertexNum: number = 10; //扇形的顶点数
var angle: number = Math.PI * 2 / vertexNum; //每个顶点的角度
var vertices: Float32Array = new Float32Array((vertexNum + 1) * 3); //顶点数组
var indices: Uint16Array = new Uint16Array(vertexNum * 3); //索引数组

vertices[0] = 0; //扇形中心点
vertices[1] = 0;
vertices[2] = 0;

for (var i = 0; i <= vertexNum; i++) {
    var p: Vector3 = new Vector3(Math.cos(i * angle), 0, Math.sin(i * angle)); //计算每个顶点的坐标
    vertices[(i + 1) * 3] = p.x;
    vertices[(i + 1) * 3 + 1] = p.y;
    vertices[(i + 1) * 3 + 2] = p.z;
    if (i < vertexNum) {
        indices[i * 3] = 0; //扇形中心点的索引为0
        indices[i * 3 + 1] = i + 1;
        indices[i * 3 + 2] = i + 2;
    }
}

创建Mesh对象，并设置顶点和索引。

//创建Mesh对象，并设置顶点和索引
var vertexDeclaration: VertexMesh = VertexMesh.getVertexDeclaration("POSITION");
var vertexBuffer: VertexBuffer3D = new VertexBuffer3D(vertexDeclaration, vertexNum + 1);
var indexBuffer: IndexBuffer3D = new IndexBuffer3D(IndexBuffer3D.INDEXTYPE_USHORT, vertexNum * 3, IndexBuffer3D.DYNAMIC);

vertexBuffer.setData(vertices.buffer);
indexBuffer.setData(indices.buffer);

var mesh: Mesh = new Mesh();
mesh._vertexBuffer = vertexBuffer;
mesh._indexBuffer = indexBuffer;
mesh._setBuffer(vertexBuffer, indexBuffer);

创建MeshSprite3D对象，并设置材质。

//创建MeshSprite3D对象，并设置材质
var meshSprite: MeshSprite3D = new MeshSprite3D(mesh);
meshSprite.transform.position = new Vector3(0, 0, 0);
scene.addChild(meshSprite);

var material: Laya.BlinnPhongMaterial = new Laya.BlinnPhongMaterial();
material.albedoColor = new Laya.Vector4(1, 0, 0, 1); //设置颜色为红色
meshSprite.meshRenderer.material = material;

运行程序，查看效果。

完整代码如下：

//导入引擎库
import Scene = Laya.Scene;
import MeshSprite3D = Laya.MeshSprite3D;
import Vector3 = Laya.Vector3;
import Sprite3D = Laya.Sprite3D;
import Mesh = Laya.Mesh;
import VertexMesh = Laya.VertexMesh;
import IndexBuffer3D = Laya.IndexBuffer3D;
import VertexBuffer3D = Laya.VertexBuffer3D;

//创建场景
var scene: Scene = Laya.stage.addChild(new Scene()) as Scene;

//创建扇形的顶点和索引
var vertexNum: number = 10; //扇形的顶点数
var angle: number = Math.PI * 2 / vertexNum; //每个顶点的角度
var vertices: Float32Array = new Float32Array((vertexNum + 1) * 3); //顶点数组
var indices: Uint16Array = new Uint16Array(vertexNum * 3); //索引数组

vertices[0] = 0; //扇形中心点
vertices[1] = 0;
vertices[2] = 0;

for (var i = 0; i <= vertexNum; i++) {
    var p: Vector3 = new Vector3(Math.cos(i * angle), 0, Math.sin(i * angle)); //计算每个顶点的坐标
    vertices[(i + 1) * 3] = p.x;
    vertices[(i + 1) * 3 + 1] = p.y;
    vertices[(i + 1) * 3 + 2] = p.z;
    if (i < vertexNum) {
        indices[i * 3] = 0; //扇形中心点的索引为0
        indices[i * 3 + 1] = i + 1;
        indices[i * 3 + 2] = i + 2;
    }
}

//创建Mesh对象，并设置顶点和索引
var vertexDeclaration: VertexMesh = VertexMesh.getVertexDeclaration("POSITION");
var vertexBuffer: VertexBuffer3D = new VertexBuffer3D(vertexDeclaration, vertexNum + 1);
var indexBuffer: IndexBuffer3D = new IndexBuffer3D(IndexBuffer3D.INDEXTYPE_USHORT, vertexNum * 3, IndexBuffer3D.DYNAMIC);

vertexBuffer.setData(vertices.buffer);
indexBuffer.setData(indices.buffer);

var mesh: Mesh = new Mesh();
mesh._vertexBuffer = vertexBuffer;
mesh._indexBuffer = indexBuffer;
mesh._setBuffer(vertexBuffer, indexBuffer);

//创建MeshSprite3D对象，并设置材质
var meshSprite: MeshSprite3D = new MeshSprite3D(mesh);
meshSprite.transform.position = new Vector3(0, 0, 0);
scene.addChild(meshSprite);

var material: Laya.BlinnPhongMaterial = new Laya.BlinnPhongMaterial();
material.albedoColor = new Laya.Vector4(1, 0, 0, 1); //设置颜色为红色
meshSprite.meshRenderer.material = material;
``