在 XNA 中旋转播放器

Question

我一直在寻找有关如何正确执行此操作的教程，但 Google 一直空无一物。也许这是一个非常简单的主题，但我不知道该怎么做。

到目前为止，我发现的代码如下所示：

        if (currentKeyboardState.IsKeyDown(Keys.A))
        {
            RotationAngle += 0.01f;
            float circle = MathHelper.Pi * 2;
            RotationAngle = RotationAngle % circle;
        }

只是，这并没有多大作用。它来自MSDN。这是我能找到的最好看的解决方案。

我想要做的就是让玩家旋转他们的船并朝另一个方向射击。 我正在制作一款与小行星非常相似的游戏，但目前我只能朝一个方向射击。

任何帮助将不胜感激:)

编辑：这是我当前的 Player.cs：

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace GameTest
{
    class Player
    {
        public Texture2D PlayerTexture;
        public Vector2 Position;
        public bool Alive;
        public int Health;
        public Vector2 origin;
        public float RotationAngle;
        KeyboardState currentKeyboardState;
        KeyboardState previousKeyboardState;
        public int Width
        {
            get { return PlayerTexture.Width; }
        }
        public int Height
        {
            get { return PlayerTexture.Height; }
        }


        public void Initialize(Texture2D texture, Vector2 position)
        {
            PlayerTexture = texture;

            Position = position;

            Alive = true;

            Health = 10;

            origin.X = PlayerTexture.Width / 2;
            origin.Y = PlayerTexture.Height / 2;
        }

        public void Update(GameTime gameTime)
        {
            RotationAngle += 10f;

            previousKeyboardState = currentKeyboardState;
            currentKeyboardState = Keyboard.GetState();

            float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;

            if (currentKeyboardState.IsKeyDown(Keys.A))
            {

                //float circle = MathHelper.Pi * 2;
                //RotationAngle = RotationAngle % circle;
            }

            if (currentKeyboardState.IsKeyDown(Keys.D))
            {
                //rotation
            }
        }

        public void Draw(SpriteBatch spriteBatch)
        {
            spriteBatch.Draw(PlayerTexture, Position, null, Color.White, RotationAngle, origin, 1f, SpriteEffects.None, 0f);
        }
    }
}

Answer 1

我的猜测是您缺少“原点”或旋转中心：

RotationAngle += .5f;
float circle = MathHelper.Pi * 2;
RotationAngle = RotationAngle % circle;

Vector2 origin = new Vector2(texture.Width / 2, texure.Height / 2);

spriteBatch.Draw(texture, position, null, Color.White, RotationAngle, origin, 1.0f, SpriteEffects.None, 0f);

至于你想要拍摄的角度，你需要一些几何形状（类似这样的东西，没有测试过......但如果我没记错的话）：

Vector2 velocity = new Vector2(speed*Math.Cos(RotationAngle), speed*Math.Sin(RotationAngle));

另外，使用调试器确保旋转角度正确变化。