如何在XNA中逐个像素地绘制？

Question

我正在尝试使用XNA逐个像素地在屏幕上绘图,但是我遇到了资源问题.我认为最好的方法是使用1个纹理来更新每一帧,但是我无法更新它.这是我到目前为止所做的,就像测试一样:

Texture2D canvas;
Rectangle tracedSize;
UInt32[] pixels;

protected override void Initialize()
    {
        tracedSize = GraphicsDevice.PresentationParameters.Bounds;
        canvas = new Texture2D(GraphicsDevice, tracedSize.Width, tracedSize.Height, false, SurfaceFormat.Color);
        pixels = new UInt32[tracedSize.Width * tracedSize.Height];               

        base.Initialize();
    }

protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);

        pixels[100] = 0xFF00FF00;
        canvas.SetData<UInt32>(pixels, 0, tracedSize.Width * tracedSize.Height);

        spriteBatch.Begin();
        spriteBatch.Draw(canvas, new Rectangle(0, 0, tracedSize.Width, tracedSize.Height), Color.White);
        spriteBatch.End();

        base.Draw(gameTime);
    }

当第二次调用Draw()时,我收到以下错误:

"操作已中止.您不能修改已在设备上设置的资源,也不能修改在平铺括号内使用的资源."

如果我尝试在Draw()中创建一个新的Texture2D,我很快就会出现内存不足错误.这适用于Windows Phone.看起来我试图以错误的方式做到这一点,我还有什么其他选择才能让它发挥作用？

Answer 1

GraphicsDevice.Textures[0] = null在调用SetData之前尝试设置.根据您之后可能有更高效的方法的效果,您还可以考虑Silverlight WriteableBitmap.

编辑:这是我在模拟器中测试的代码:

Texture2D canvas;
Rectangle tracedSize;
UInt32[] pixels;

protected override void Initialize()
{
    tracedSize = GraphicsDevice.PresentationParameters.Bounds;
    canvas = new Texture2D(GraphicsDevice, tracedSize.Width, tracedSize.Height, false, SurfaceFormat.Color);
    pixels = new UInt32[tracedSize.Width * tracedSize.Height];

    base.Initialize();
}
Random rnd = new Random();
protected override void Draw(GameTime gameTime)
{
    GraphicsDevice.Clear(Color.CornflowerBlue);

    GraphicsDevice.Textures[0] = null;
    pixels[rnd.Next(pixels.Length)] = 0xFF00FF00;
    canvas.SetData<UInt32>(pixels, 0, tracedSize.Width * tracedSize.Height);

    spriteBatch.Begin();
    spriteBatch.Draw(canvas, new Rectangle(0, 0, tracedSize.Width, tracedSize.Height), Color.White);
    spriteBatch.End();

    base.Draw(gameTime);
}