VCS/XnaSphere4 - Sample is best!

開発環境	Microsoft Visual C# 2010 Express (SP1)
実行環境	Microsoft Windows XP Home Edition (SP3)
プロジェクトの種類	Windows Game (4.0)
プロジェクト名	XnaSphere

インデクス化のヒント

頂点座標を引数にインデクス番号を返す関数を用意する。
球形の距離(r^2=x^2+y^2+z^2)が一定の閾値内の頂点があればそのインデクスを、
無ければ頂点座標を登録しそのインデクスを返す。

Game1.cs

// XnaSphere4 - XNA 球体(再帰分割slerp)
using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
 
namespace XnaSphere
{
    class Game1 : Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch sprite;
        SpriteFont font;
        BasicEffect effect;
 
        VertexBuffer vertexBuffer;
        VertexPositionColor[] vertices;
        int vi = 0;
 
        // fps
        int sec;
        int draw = 0;
        int fps = 0;
 
        // カメラ
        int camLat = 0;
        int camLong = 90;
        float camDist = 5;
 
        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            graphics.PreferredBackBufferWidth = 1280;
            graphics.PreferredBackBufferHeight = 720;
            Content.RootDirectory = "Content";
            IsMouseVisible = true;
        }
 
        protected override void LoadContent()
        {
            font = Content.Load<SpriteFont>("SpriteFont1");
            sprite = new SpriteBatch(GraphicsDevice);
            effect = new BasicEffect(GraphicsDevice);
            //effect.VertexColorEnabled = true;
            //effect.EnableDefaultLighting();
            effect.Projection = Matrix.CreatePerspectiveFieldOfView(
                MathHelper.ToRadians(45), GraphicsDevice.Viewport.AspectRatio, 1, 100);
 
            // 頂点バッファ
            int lv = 4;
            vertices = new VertexPositionColor[3 * 8 * (int)Math.Pow(4, lv)];
            GenerateTriangle(lv, Vector3.Up, new Vector3(1, 0, 0), new Vector3(0, 0, 1));
            GenerateTriangle(lv, Vector3.Up, new Vector3(0, 0, 1), new Vector3(-1, 0, 0));
            GenerateTriangle(lv, Vector3.Up, new Vector3(-1, 0, 0), new Vector3(0, 0, -1));
            GenerateTriangle(lv, Vector3.Up, new Vector3(0, 0, -1), new Vector3(1, 0, 0));
            GenerateTriangle(lv, Vector3.Down, new Vector3(0, 0, 1), new Vector3(1, 0, 0));
            GenerateTriangle(lv, Vector3.Down, new Vector3(-1, 0, 0), new Vector3(0, 0, 1));
            GenerateTriangle(lv, Vector3.Down, new Vector3(0, 0, -1), new Vector3(-1, 0, 0));
            GenerateTriangle(lv, Vector3.Down, new Vector3(1, 0, 0), new Vector3(0, 0, -1));
 
            vertexBuffer = new VertexBuffer(GraphicsDevice,
                typeof(VertexPositionColor), vertices.Length, BufferUsage.WriteOnly);
            vertexBuffer.SetData(vertices);
 
            base.LoadContent();
        }
 
        void GenerateTriangle(int lv, Vector3 v1, Vector3 v2, Vector3 v3)
        {
            if (lv-- <= 0)
            {
                vertices[vi++] = new VertexPositionColor(v1, Color.Yellow);
                vertices[vi++] = new VertexPositionColor(v2, Color.Yellow);
                vertices[vi++] = new VertexPositionColor(v3, Color.Yellow);
                return;
            }
            Vector3 v4 = QV(Quaternion.Slerp(VQ(v1), VQ(v2), 0.5f));
            Vector3 v5 = QV(Quaternion.Slerp(VQ(v2), VQ(v3), 0.5f));
            Vector3 v6 = QV(Quaternion.Slerp(VQ(v3), VQ(v1), 0.5f));
            GenerateTriangle(lv, v1, v4, v6);
            GenerateTriangle(lv, v2, v5, v4);
            GenerateTriangle(lv, v3, v6, v5);
            GenerateTriangle(lv, v4, v5, v6);
        }
 
        Quaternion VQ(Vector3 v)
        {
            return new Quaternion(v.X, v.Y, v.Z, 0);
        }
 
        Vector3 QV(Quaternion q)
        {
            return new Vector3(q.X, q.Y, q.Z);
        }
 
        protected override void Update(GameTime gameTime)
        {
            KeyboardState kState = Keyboard.GetState();
            if (kState.IsKeyDown(Keys.Escape)) Exit();
            if (kState.IsKeyDown(Keys.Up)) camLat = Math.Min(camLat + 1, 89);
            if (kState.IsKeyDown(Keys.Down)) camLat = Math.Max(camLat - 1, -89);
            if (kState.IsKeyDown(Keys.Left)) camLong = (camLong + 1) % 360;
            if (kState.IsKeyDown(Keys.Right)) camLong = (camLong + 359) % 360;
            if (kState.IsKeyDown(Keys.PageUp)) camDist -= 0.1f;
            if (kState.IsKeyDown(Keys.PageDown)) camDist += 0.1f;
 
            base.Update(gameTime);
        }
 
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);
            GraphicsDevice.RasterizerState =
                new RasterizerState { FillMode = FillMode.WireFrame };
 
            // カメラ位置
            float rad = MathHelper.ToRadians(camLat);
            float y = (float)Math.Sin(rad) * camDist;
            float r = (float)Math.Cos(rad) * camDist;
            rad = MathHelper.ToRadians(camLong);
            float x = (float)Math.Cos(rad) * r;
            float z = (float)Math.Sin(rad) * r;
            effect.View = Matrix.CreateLookAt(new Vector3(x, y, z), Vector3.Zero, Vector3.Up);
 
            GraphicsDevice.SetVertexBuffer(vertexBuffer);
 
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleList,
                    0, vertexBuffer.VertexCount / 3);
            }
 
            // fps
            draw++;
            if (gameTime.TotalGameTime.Seconds != sec)
            {
                fps = draw;
                draw = 0;
                sec = gameTime.TotalGameTime.Seconds;
            }
 
            sprite.Begin();
            string text = String.Format(
                "fps={0} lat={1} long={2} dist={3:f1}", fps, camLat, camLong, camDist);
            sprite.DrawString(font, text, new Vector2(0, 0), Color.White);
            sprite.End();
 
            base.Draw(gameTime);
        }
    }
}