ZuneでLine関数が無いので作ってみよう


点A(x1,y1)と点B(x2、y2)の線を引きたい場合、そのまま線を引く関数が無いので角度raと長さrを求めて、これを使ってラインを表現して見ます。

namespace LineTest
{
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        private Texture2D linePoint;
        private Rectangle lineDrawArea = new Rectangle();
        private Rectangle lineSrcArea = new Rectangle();
        private Vector2 lineCenter = new Vector2(0, 0);
        private SpriteEffects lineSpEffect = new SpriteEffects();

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
            graphics.PreferredBackBufferWidth = 240;
            graphics.PreferredBackBufferHeight = 320;
            // Frame rate is 30 fps by default for Zune.
            TargetElapsedTime = TimeSpan.FromSeconds(1 / 30.0);
        }

        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(GraphicsDevice);
            linePoint= Content.Load<Texture2D>("Point");
            lineSrcArea.X = 0;
            lineSrcArea.Y = 0;
            lineSrcArea.Width = 1;
            lineSrcArea.Height = 1;
            lineDrawArea.Height = 1;
        }

        protected override void Update(GameTime gameTime)
        {
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();
            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);
            spriteBatch.Begin();
            for (int i = 0; i < 320; i += 8)
                drawLine(0, 0, 240, i, Color.White);
            spriteBatch.End();
            base.Draw(gameTime);
        }

        //-------------------------------------------------------------------------------
        //ラインを引く
        //-------------------------------------------------------------------------------
        private void drawLine(int x1, int y1, int x2, int y2, Color lineColor)
        {
            double   r,ra;
            int x, y;

            x = x2 - x1;
            y = y2 - y1;
            r  =Math.Sqrt(x * x + y * y);
            ra = (x > 0) ? Math.Asin(y / rr) : Math.PI - Math.Asin(y / rr);
            lineDrawArea.X = x1;
            lineDrawArea.Y = y1;
            lineDrawArea.Width = (int)r;
            spriteBatch.Draw(linePoint, lineDrawArea, lineSrcArea, lineColor, (float)ra, lineCenter, lineSpEffect, 0);
        }
    }
}

ここで"point"という画像ファイルを参照していますが、これが1X1ピクセルの白いPNGファイルです。

linePoint = Content.Load<Texture2D>("Point");

これを動かすと、

こうなり、Line関数が擬似的に完成