一.要点
绘制立方体(或其他3D图形)的方法与绘制三角形的方法类似,任何一个3D图形的轮廓都有一系列三角形构成.为减少数据冗余,在绘制复杂3D图形时,应使用
GraphicsDevice.DrawIndexedPrimitives()方法，而不是绘制三角形时所使用的GraphicsDevice.DrawUserPrimitives()。
二.实现代码
1.为Game类添加成员变量:
1: VertexPositionColor[] vertexList;
2: VertexBuffer vertexBuffer;
3: ushort[] indexList;
4: IndexBuffer indexBuffer;
2.在LoadContent()方法中定义立方体六个顶点的座标
1: vertexList = new VertexPositionColor[]
2: {
3: new VertexPositionColor(new Vector3(1f,1f,-1f),Color.Red),
4: new VertexPositionColor(new Vector3(1f,-1f,-1f),Color.Red),
5: new VertexPositionColor(new Vector3(-1f,-1f,-1f),Color.Red),
6: new VertexPositionColor(new Vector3(-1f,1f,-1f),Color.Red),
7: new VertexPositionColor(new Vector3(1f,1f,1f),Color.Red),
8: new VertexPositionColor(new Vector3(1f,-1f,1f),Color.Red),
9: new VertexPositionColor(new Vector3(-1f,-1f,1f),Color.Red),
10: new VertexPositionColor(new Vector3(-1f,1f,1f),Color.Red)
11: };
12: vertexBuffer = new VertexBuffer(
13: GraphicsDevice,
14: typeof(VertexPositionColor),
15: vertexList.Length,
16: BufferUsage.None);
17: vertexBuffer.SetData<VertexPositionColor>(vertexList);
3.定义顶点索引数组：
1: indexList = new ushort[]
2: {
3: 0,1,2,0,2,3,
4: 7,4,5,7,5,6,
5: 0,1,5,0,5,4,
6: 7,3,2,7,2,6,
7: 0,4,7,0,7,3,
8: 2,1,5,2,5,6
9: };
10: indexBuffer = new IndexBuffer(
11: GraphicsDevice,
12: typeof(ushort),
13: indexList.Length,
14: BufferUsage.None);
15: indexBuffer.SetData<ushort>(indexList);
4.在Draw()方法中添加绘制代码：
1: GraphicsDevice.SetVertexBuffer(vertexBuffer);
2: GraphicsDevice.Indices = indexBuffer;
3:
4: int primitiveCount = indexList.Length / 3;
5: foreach (var pass in basicEffect.CurrentTechnique.Passes)
6: {
7: pass.Apply();
8: GraphicsDevice.DrawIndexedPrimitives(
9: PrimitiveType.TriangleList,
10: 0,
11: 0,
12: vertexList.Length,
13: 0,
14: primitiveCount);
15: }
