Question

我需要一种针对第三人称相机的非语言特定算法。我遇到的问题是如何将相机保持在物体后面并保持相机的旋转与物体旋转相同。任何想法？

示例：

UpdateCamera(camera, target){
    offset = vector(0,height,distance);
    cameraPos = targetPos+offset;
    camAngle = ?????;
}

我知道它不会那么简单，但我相信你会得到它的要点。

Answer 1

最简单的假设你有一个简单的NUV摄像机类：

/// <summary>
/// An instance of this class represents a camera for a 3D view.
/// Cameras are defined with a position and three mutually-orthogonal
/// axes, namely N (points in the direction faced by the camera),
/// U (points to the left of the camera) and V (points to the top
/// of the camera).
/// </summary>
sealed class Camera
{
    //#################### PRIVATE VARIABLES ####################
    #region

    private Vector3 m_n;
    private Vector3 m_position;
    private Vector3 m_u;
    private Vector3 m_v;

    #endregion

    //#################### PROPERTIES ####################
    #region

    /// <summary>
    /// The position of the camera.
    /// </summary>
    public Vector3 Position { get { return m_position; } }

    /// <summary>
    /// A vector pointing in the direction faced by the camera.
    /// </summary>
    public Vector3 N { get { return m_n; } }

    /// <summary>
    /// A vector pointing to the left of the camera.
    /// </summary>
    public Vector3 U { get { return m_u; } }

    /// <summary>
    /// A vector pointing to the top of the camera.
    /// </summary>
    public Vector3 V { get { return m_v; } }

    #endregion

    //#################### CONSTRUCTORS ####################
    #region

    /// <summary>
    /// Constructs a new camera.
    /// </summary>
    /// <param name="position">The position of the camera.</param>
    /// <param name="look">A vector pointing in the direction faced by the camera.</param>
    /// <param name="up">The "up" direction for the camera.</param>
    public Camera(Vector3 position, Vector3 look, Vector3 up)
    {
        m_position = position;

        m_n = look;
        m_n.Normalize();

        m_v = up;
        m_v.Normalize();

        m_u = Vector3.Cross(m_v, m_n);
        m_u.Normalize();
    }

    #endregion

    //#################### PUBLIC METHODS ####################
    #region

    /// <summary>
    /// Moves the camera by the specified displacement in the n direction.
    /// </summary>
    /// <param name="delta">The displacement by which to move.</param>
    public void MoveN(float delta)
    {
        m_position += delta * m_n;
    }

    /// <summary>
    /// Moves the camera by the specified displacement in the u direction.
    /// </summary>
    /// <param name="delta">The displacement by which to move.</param>
    public void MoveU(float delta)
    {
        m_position += delta * m_u;
    }

    /// <summary>
    /// Moves the camera by the specified displacement in the v direction.
    /// </summary>
    /// <param name="delta">The displacement by which to move.</param>
    public void MoveV(float delta)
    {
        m_position += delta * m_v;
    }

    /// <summary>
    /// Rotates the camera anticlockwise by the specified angle about the specified axis.
    /// </summary>
    /// <param name="axis">The axis about which to rotate.</param>
    /// <param name="angle">The angle by which to rotate (in radians).</param>
    public void Rotate(Vector3 axis, float angle)
    {
        // Note: We try and optimise things a little by observing that there's no point rotating an axis about itself.
        if(axis != m_n) m_n = MathUtil.RotateAboutAxis(m_n, angle, axis);
        if(axis != m_u) m_u = MathUtil.RotateAboutAxis(m_u, angle, axis);
        if(axis != m_v) m_v = MathUtil.RotateAboutAxis(m_v, angle, axis);
    }

    #endregion
}

现在，每一帧：

1）获取玩家的位置pp和方向pdir 2）重新创建位置= pp - offset * pdir，look = pdir并向上=合理的（例如(0,0,1)）的相机。

三角学3d数学第三人称相机算法

1 个答案: