Question

我正在尝试使用可移动相机在屏幕上正确绘制一些3D模型，但遇到两个问题。第一个问题立即可见：模型应该是立方体，但绘制为矩形棱柱。就像它们被挤压/压缩一样，但我找不到原因。

第二个问题出现在俯视“立方体”时。尽管它们应该只是旋转，但它们似乎在旋转时以一种奇怪的方式伸展。

Still looking down, but rotated CW 90 degrees

这是我的相机代码：

public class Camera
{
    private Driver Driver;
    private int ScreenWidth { get { return Driver.GraphicsDevice.Viewport.Width; } }
    private int ScreenHeight { get { return Driver.GraphicsDevice.Viewport.Height; } } 

    public Matrix ViewMatrix { get; private set; }
    public Matrix ProjectionMatrix { get; private set; }

    private const float NearClippingPlane = 0.1f;
    private const float FarClippingPlane = 200.0f;

    public Vector3 Position { get; private set; }

    private Vector3 _direction; // Do not use _direction!
    private Vector3 Direction
    {
        get { return _direction; }
        set
        {
            if (value == Vector3.Zero) { }
            else
            {
                var normalizedTemp = value;
                normalizedTemp.Normalize();

                if (normalizedTemp.Y > -.9999f) _direction = normalizedTemp;
            }
        }
    }

    private Vector3 Up;

    private const float MovementSpeed = 10f;
    private const float PanSpeed = 10f;

    private MouseState previousMouseState;

    private Vector3 HorizontalPlaneDirection
    {
        get
        {
            var direction = new Vector3(Direction.X, 0, Direction.Z);
            if (direction != Vector3.Zero)
                direction.Normalize();
            return direction;
        }
    }

    public Camera(Driver game, Vector3 position, Vector3 target, Vector3 up)
    {
        Driver = game;

        // Build camera view matrix
        Position = position;
        Direction = target - position;
        Up = up;
        CreateLookAt();

        ProjectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(60), ScreenWidth / ScreenHeight, NearClippingPlane, FarClippingPlane);
    }

    public void Initialize()
    {
        // Set mouse position and do initial get state
        Mouse.SetPosition(ScreenWidth / 2, ScreenHeight / 2);

        previousMouseState = Mouse.GetState();
    }

    public void Update(GameTime gameTime, KeyboardState keyboard, MouseState mouse)
    {
        float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
        float moveSpeed = MovementSpeed * elapsed;
        float panSpeed = PanSpeed * elapsed;

        if (keyboard.IsKeyDown(Keys.W))
            Position += HorizontalPlaneDirection * moveSpeed;
        if (keyboard.IsKeyDown(Keys.S))
            Position -= HorizontalPlaneDirection * moveSpeed;

        if (keyboard.IsKeyDown(Keys.A))
            Position += Vector3.Cross(Up, HorizontalPlaneDirection) * moveSpeed;
        if (keyboard.IsKeyDown(Keys.D))
            Position -= Vector3.Cross(Up, HorizontalPlaneDirection) * moveSpeed;

        if (keyboard.IsKeyDown(Keys.Space))
            Position += Up * moveSpeed;
        if (keyboard.IsKeyDown(Keys.LeftShift))
            Position -= Up * moveSpeed;

        // Rotation in the world
        Direction = Vector3.Transform(Direction, Matrix.CreateFromAxisAngle(Up, -MathHelper.ToRadians(1) * (mouse.X - previousMouseState.X) * panSpeed));

        Direction = Vector3.Transform(Direction, Matrix.CreateFromAxisAngle(Vector3.Cross(Up, HorizontalPlaneDirection), MathHelper.ToRadians(1) * (mouse.Y - previousMouseState.Y) * panSpeed));

        Driver.ResetMouseState();
        // Reset prevMouseState
        previousMouseState = Mouse.GetState();

        CreateLookAt();
    }

    private void CreateLookAt()
    {
        ViewMatrix = Matrix.CreateLookAt(Position, Position + Direction, Up);
    }
}

以及绘制模型的代码：

public void Draw(Camera Camera)
    {
        foreach (var mesh in Model.Meshes)
        {
            foreach (BasicEffect effect in mesh.Effects)
            {
                //effect.EnableDefaultLighting();
                //effect.PreferPerPixelLighting = true;

                effect.World = GetWorldMatrix();
                effect.View = Camera.ViewMatrix;
                effect.Projection = Camera.ProjectionMatrix;
            }

            mesh.Draw();
        }
    }

我知道代码位很长，可能很难通过，但是我非常感谢您的帮助。谢谢！

Answer 1

嗯，我很傻。解决方案很简单-问题在于投影矩阵。

在我的代码中，当我设置ProjectionMatrix时，将其长宽比设置为ScreenWidth / ScreenHeight。但是，由于这两个都是整数，因此结果也是也是整数。因此，不是将ScreenWidth / ScreenHeight的非整数结果设为16：9的适当宽高比，而是将其强制转换为整数，而我的宽高比最终变为ScreenWidth / ScreenHeight = 1920 / 1080 = (int)1.7778 = 1。

显然，解决方案很简单。将浮标放置到除数上，您将得到正确的答案。 ScreenWidth / (float)ScreenHeight = 1920 / 1080.0f = 1.7778f。

我希望我的挣扎之日能够帮助其他人解决这个问题。另外，如果在XNA中创建3D相机时遇到其他问题，建议您查看this代码示例。它是为手机设计的（出于某种原因？），它是一个DLL，这意味着您将无法运行它（您必须添加一个可执行项目，引用该DLL并以任何方式重建该可执行项目。您可以对DLL进行编辑），但是它仍然是一个很好的起点/参考点。

Glorious correctly-aspected cubes

XNA / Monogame 3D拉伸和宽高比

1 个答案: