Question

我正在尝试在视口中心附近支持缩放和旋转我的相机类。

在我的应用程序中，我已经在输入SpriteBatch.Begin代码之前手动定位精灵，根据摄像头的位置（使剔除更容易实现）。虽然每个精灵都是手动定位的，但我宁愿不单独旋转和缩放每个精灵。

因此我试图在SpriteBatch.Begin方法上使用matrixTransform参数。

下面是我用来说明问题的硬编码应用程序（使用Car.png内容图像）。旋转速度不如我预期的那么快（每帧旋转10度？），并且旋转/放大左上角。我希望它围绕屏幕中心旋转，这将始终保持中间车在中心，并从那一点开始缩放。

我尝试了几种创建矩阵翻译的组合，按视口的中途距离重新排序/添加/乘法/翻译，但我真的不明白矩阵是如何工作的。我也在几个网站上尝试过这些解决方案，但我还没有成功为我工作。

有人可以告诉我我必须创建的矩阵翻译，或者指向我认为适合我的设置的网站方向吗？

用于演示此问题的Windows XNA应用程序：

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace RenderTest
{
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        Texture2D _carTexture;
        float _zoom = 1.0f;
        float _rotationInDegrees = 0.0f;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(GraphicsDevice);
            _carTexture = Content.Load<Texture2D>("Car");
        }

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

            if (Keyboard.GetState(PlayerIndex.One).IsKeyDown(Keys.Up)) // Zoom in key
                _zoom *= 1.1f;

            if (Keyboard.GetState(PlayerIndex.One).IsKeyDown(Keys.Down)) // Zoom out key
                _zoom /= 1.1f;

            if (Keyboard.GetState(PlayerIndex.One).IsKeyDown(Keys.Left)) // Rotate anticlockwise key
                _rotationInDegrees -= 10;

            if (Keyboard.GetState(PlayerIndex.One).IsKeyDown(Keys.Right)) // Rotate clockwise key
                _rotationInDegrees += 10;

            base.Update(gameTime);
        }

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

            spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.None, RasterizerState.CullNone, null, GetMatrix(GraphicsDevice));

            spriteBatch.Draw(_carTexture, new Rectangle(0, 0, 50, 50), Color.White);//Square car placed top left
            spriteBatch.Draw(_carTexture, new Rectangle(GraphicsDevice.Viewport.Width / 2 - 25, GraphicsDevice.Viewport.Height / 2 - 50, 50, 100), Color.Green);//Car placed centre
            spriteBatch.Draw(_carTexture, new Rectangle(GraphicsDevice.Viewport.Width / 2 + 100, GraphicsDevice.Viewport.Height / 2 + 100, 50, 50), Color.Black);//Off centre but always within screen

            spriteBatch.End();

            base.Draw(gameTime);
        }

        Matrix GetMatrix(GraphicsDevice graphicsDevice)
        {
            Matrix translationMatrix = Matrix.CreateTranslation(0, 0, 0);
            Matrix rotationMatrix = Matrix.CreateRotationZ(MathHelper.ToRadians(MathHelper.ToRadians(_rotationInDegrees)));
            Matrix zoomMatrix = Matrix.CreateScale(_zoom);

            Matrix compositeMatrix = translationMatrix * rotationMatrix * zoomMatrix;

            return compositeMatrix;
        }
    }
}

谢谢，

利

解决方案

    Matrix GetMatrix(GraphicsDevice graphicsDevice)
    {
        Matrix translateToOrigin = Matrix.CreateTranslation(-graphicsDevice.Viewport.Width / 2, -graphicsDevice.Viewport.Height / 2, 0);
        Matrix rotationMatrix = Matrix.CreateRotationZ(MathHelper.ToRadians(_rotationInDegrees));
        Matrix zoomMatrix = Matrix.CreateScale(_zoom);
        Matrix translateBackToPosition = Matrix.CreateTranslation(graphicsDevice.Viewport.Width / 2, graphicsDevice.Viewport.Height / 2, 0);

        Matrix compositeMatrix = translateToOrigin * rotationMatrix * zoomMatrix * translateBackToPosition;

        return compositeMatrix;
    }

Answer 1

每次都应使用相同的Rectangle，并在矩阵中进行定位。

这样做的原因是矩阵在使用矩形定位后会应用于精灵。所有后续矩阵运算都会将（0,0）视为原点，而不是您所期望的纹理中心。

XNA绕中心旋转2d

1 个答案: