XNA - 矩阵相当于SpriteBatch.Draw转换?

时间:2012-03-01 03:52:49

标签: c# matrix xna transformation

说我有这个界面:

interface Drawable {
    Vector2 DrawPosition { get; }
    Texture2D Texture { get; }
    float Rotation { get; }
    Vector2 Origin { get; }
    Vector2 Scale { get; }
    bool FlipHorizontally { get; }
}

在扩展Microsoft.Xna.Framework.Game的类中,我重写了Draw(GameTime),这段代码就在那里:

Drawable d = ...;
spriteBatch.Begin();
spriteBatch.Draw(d.Texture, d.DrawPosition, new Rectangle(0, 0, d.Texture.Width, d.Texture.Height), Color.White, d.Rotation, d.Origin, d.Scale, d.FlipHorizontally ? SpriteEffects.FlipHorizontally : SpriteEffects.None, 0);
spriteBatch.End();

这使用SpriteBatch.Draw(Texture2D纹理,Vector2位置,Nullable sourceRectangle,Color color,float rotation,Vector2 origin,Vector2 scale,SpriteEffects效果,float layerDepth)重载。

假设我有一组顶点,这些顶点构成了d.Texture返回的图像的粗略轮廓(也就是说,如果我在Microsoft Paint中打开图像并从顶点集中的每个点开始,它会非常适合)。如果我想绘制这些点以便它们使用GraphicsDevice.DrawUserPrimitives()遍历纹理,是否有办法仅使用矩阵转换顶点?关键是它只能使用矩阵,我没有其他的绘图选择,因为我实际上也需要将变换后的顶点用于其他事物。我已经尝试了像

这样的东西
Matrix.CreateTranslation(new Vector3(-d.Origin, 0))
    * Matrix.CreateScale(new Vector3(d.Scale, 0))
    * Matrix.CreateRotationZ(d.Rotation)
    * Matrix.CreateTranslation(new Vector3(d.DrawPosition, 0)));

但它很难完成。这个问题有解决方案吗?

2 个答案:

答案 0 :(得分:2)

您的矩阵代码适用于 World 矩阵(将模型放置在世界空间中)。所以我猜这是其中之一:

  • 您的基元在模型空间中位于错误的位置。 Sprite批处理创建一个多边形,其中(0,0)是精灵的左上角,({texture width},{texture height})是右下角。你的原语需要大小和位置相同。

  • 您的投影矩阵错误。见this answer。请注意,SpriteBatch使用翻转(客户端空间)坐标系。

  • 您的背面剔除模式错误(不考虑翻转坐标系)。

  • 您遇到了深度缓冲问题(您需要在远处和近处飞机上绘图,并且您是否被任何东西深度剔除?)

如果您仍有问题,请从DirectX SDK获取PIX并使用它来识别您的游戏实际绘制的内容。

答案 1 :(得分:0)

噢,天哪,我很抱歉。我刚刚意识到它不匹配的全部原因是因为我使顶点错了!好吧,我想如果你们需要帮助做同样的事情,这是我的最终版本:

abstract class Drawable
{
    public abstract Vector2 DrawPosition { get; }
    public abstract Texture2D Texture { get; }
    public abstract float Rotation { get; }
    public abstract Vector2 Origin { get; }
    public abstract Vector2 Scale { get; }
    public abstract bool FlipHorizontally { get; }

    public abstract Vector2[] Vertices { get; }

    public Matrix TransformationMatrix
    {
        get
        {
            return Matrix.CreateTranslation(-new Vector3(Texture.Width * Scale.X / 2, 0, 0))
                * Matrix.CreateScale(new Vector3(FlipHorizontally ? -1 : 1, 1, 1))
                * Matrix.CreateTranslation(new Vector3(Texture.Width * Scale.X / 2, 0, 0))
                * Matrix.CreateTranslation(-new Vector3(Origin, 0))
                * Matrix.CreateScale(new Vector3(Scale, 0))
                * Matrix.CreateRotationZ(Rotation)
                * Matrix.CreateTranslation(new Vector3(DrawPosition, 0));
        }
    }
}

class Camera
{
    private readonly Viewport viewport;

    public Matrix GetViewMatrix()
    {
        return Matrix.CreateScale(1, -1, 1) * Matrix.CreateTranslation(0, viewport.Height, 0);
    }

    public Vector2 MouseToWorld(int x, int y)
    {
        return Vector2.Transform(new Vector2(x, y), Matrix.CreateScale(1, -1, 1) * Matrix.CreateTranslation(0, viewport.Height, 0));
    }
}

class Game1 : Microsoft.Xna.Framework.Game
{
    private Drawable avatar;
    private Camera camera;
    ...
    protected override void Initialize() {
        avatar = ...;
        camera = new Camera(graphics.GraphicsDevice.Viewport);
        basicEffect = new BasicEffect(graphics.GraphicsDevice);
        basicEffect.VertexColorEnabled = true;
        basicEffect.Projection = Matrix.CreateOrthographicOffCenter(0, graphics.GraphicsDevice.Viewport.Width, graphics.GraphicsDevice.Viewport.Height, 0, 0, 1);

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

        spriteBatch.Begin(SpriteSortMode.Deferred, null, null, null, null, null, camera.GetViewMatrix());
        spriteBatch.Draw(avatar.Texture, avatar.DrawPosition, new Rectangle(0, 0, avatar.Texture.Width, avatar.Texture.Height), Color.White, avatar.Rotation, avatar.Origin, avatar.Scale, avatar.FlipHorizontally ? SpriteEffects.FlipHorizontally : SpriteEffects.None, 0);
        spriteBatch.End();

        basicEffect.CurrentTechnique.Passes[0].Apply();
        VertexPositionColor[] vertices = new VertexPositionColor[avatar.Vertices.Length + 1];
        Matrix m = MakeAffineTransform(avatar);
        for (int i = 0; i < avatar.Vertices.Length; i++)
        {
            vertices[i] = new VertexPositionColor(Vector3.Transform(new Vector3(Vector2.Transform(avatar.Vertices[i], m), 0), camera.GetViewMatrix()), Color.Black);
            Console.WriteLine(vertices[i]);
        }
        vertices[vertices.Length - 1] = vertices[0];
        graphics.GraphicsDevice.DrawUserPrimitives<VertexPositionColor>(PrimitiveType.LineStrip, vertices, 0, vertices.Length - 1);

        base.Draw(gameTime);
    }
    ...
}

效果很好!这实际上会翻转原点,使其位于左下角并翻转y轴,以便增加值向上,减少值向下。相机可以是一个很好的基础,可以很容易地更新(例如,如果你想让它跟随屏幕上的某些东西),这样你就可以将世界坐标传递给它(原点在左下角)并且它' ll返回屏幕坐标。