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我已经被一个问题困住了几个小时了。我需要将我的 4x4 矩阵（模型、视图、投影）转换为带有平移向量的 3x3 矩阵。我需要这样做，因为我使用的 API 没有 4x4 矩阵类及其完全封闭的源代码。

奇怪的是，他们的 LookAt 函数声明它根本不影响矩阵的平移部分。我用来渲染的 4x4 矩阵有它（一切都渲染 100% 正确）。

有人可以看看我的转换函数，看看我做错了什么吗？谢谢

CIwFMat ConvertToMarmaladeFormat(Matrix4& Mat)
{
    CIwFMat M;

    M.m[0][0] = Mat[0][0];
    M.m[0][1] = Mat[0][1];
    M.m[0][2] = Mat[0][2];

    M.m[1][0] = Mat[1][0];
    M.m[1][1] = Mat[1][1];
    M.m[1][2] = Mat[1][2];

    M.m[2][0] = Mat[2][0];
    M.m[2][1] = Mat[2][1];
    M.m[2][2] = Mat[2][2];

    M.t = CIwFVec3(Mat[3][0], Mat[3][1], Mat[3][2]);

    return M;
}

Matrix4 ConvertFromMarmaladeFormat(CIwFMat& M)
{
    Matrix4 Mat;
    Mat.identity();

    Mat[0][0] = M.m[0][0];
    Mat[0][1] = M.m[0][1];
    Mat[0][2] = M.m[0][2];

    Mat[1][0] = M.m[1][0];
    Mat[1][1] = M.m[1][1];
    Mat[1][2] = M.m[1][2];

    Mat[2][0] = M.m[2][0];
    Mat[2][1] = M.m[2][1];
    Mat[2][2] = M.m[2][2];

    Mat[3][0] = M.t.x;
    Mat[3][1] = M.t.y;
    Mat[3][2] = M.t.z;

    return Mat;
}

class Matrix4
{
    friend Vector4 operator*(const Vector4 &lhs, const Matrix4 &rhs);
    friend Vector3 operator*(const Vector3 &lhs, const Matrix4 &rhs);
    friend Matrix4 operator*(float scalar, const Matrix4 &rhs);

public:
    static const Matrix4 IDENTITY;
    static Matrix4 createFromAxes(const Vector3 &x, const Vector3 &y, const Vector3 &z);
    static Matrix4 createFromAxesTransposed(const Vector3 &x, const Vector3 &y, const Vector3 &z);
    static Matrix4 createFromHeadPitchRoll(float headDegrees, float pitchDegrees, float rollDegrees);
    static Matrix4 createMirror(const Vector3 &planeNormal, const Vector3 &pointOnPlane);
    static Matrix4 createOrient(const Vector3 &from, const Vector3 &to);
    static Matrix4 createRotate(const Vector3 &axis, float degrees);
    static Matrix4 createScale(float sx, float sy, float sz);
    static Matrix4 createTranslate(float tx, float ty, float tz);

    Matrix4() {}
    Matrix4(float m11, float m12, float m13, float m14,
            float m21, float m22, float m23, float m24,
            float m31, float m32, float m33, float m34,
            float m41, float m42, float m43, float m44);
    ~Matrix4() {}

    float *operator[](int row);
    const float *operator[](int row) const;

    bool operator==(const Matrix4 &rhs) const;
    bool operator!=(const Matrix4 &rhs) const;

    Matrix4 &operator+=(const Matrix4 &rhs);
    Matrix4 &operator-=(const Matrix4 &rhs);
    Matrix4 &operator*=(const Matrix4 &rhs);
    Matrix4 &operator*=(float scalar);
    Matrix4 &operator/=(float scalar);

    Matrix4 operator+(const Matrix4 &rhs) const;
    Matrix4 operator-(const Matrix4 &rhs) const;
    Matrix4 operator*(const Matrix4 &rhs) const;
    Matrix4 operator*(float scalar) const;
    Matrix4 operator/(float scalar) const;

    float determinant() const;
    void fromAxes(const Vector3 &x, const Vector3 &y, const Vector3 &z);
    void fromAxesTransposed(const Vector3 &x, const Vector3 &y, const Vector3 &z);
    void fromHeadPitchRoll(float headDegrees, float pitchDegrees, float rollDegrees);
    void identity();
    Matrix4 inverse() const;
    void orient(const Vector3 &from, const Vector3 &to);
    void rotate(const Vector3 &axis, float degrees);
    void scale(float sx, float sy, float sz);
    void toAxes(Vector3 &x, Vector3 &y, Vector3 &z) const;
    void toAxesTransposed(Vector3 &x, Vector3 &y, Vector3 &z) const;
    void toHeadPitchRoll(float &headDegrees, float &pitchDegrees, float &rollDegrees) const;
    void translate(float tx, float ty, float tz);
    Matrix4 transpose() const;

private:
    float mtx[4][4];
};

class CIwFMat
{
public:
/**
 * 3x3 rotation matrix.
 */
    float   m[3][3];
/**
 * Trans vector.
 */
    CIwFVec3    t;

...

};
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1 回答 1

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您的转换看起来不错，但请检查：

  1. Marmalade 使用行列矩阵表示法和右手轴系统（请记住您的转换）

  2. 果酱“视图”矩阵实际上不是视图矩阵，它是相机位置和方向矩阵。要获得实际的视图矩阵，应该这样做：

    CIwFMat MarmaladeView = IwGxGetViewMatrix();
CIwFMat view = (CIwFMat(CIwFMat::g_Identity, -MarmaladeView.GetTrans()) * MarmaladeView.GetTranspose()); // actually it's simple matrix inversion, but CIwFMat doesn't have Inverse() method
// in some cases your should add axis-flip transform

  3. 果酱 IwGxGetPerspectiveMatrix() 在正交投影的情况下返回无效的投影矩阵（文档没有说明这个有趣的事实）

  4. LookAt() 函数只是将矩阵的旋转部分设置为匹配 2 点之间的方向，所以手动进行平移

  5. 检查你的远/近飞机

  6. 所有 MVP 矩阵都应该由

    IwGxSetViewMatrix(); // sets view matrix view - camera position
IwGxSetModelMatrix(); // sets model matrix
IwGxSetPerspMul(); // sets perspective projection in terms of distance to view plane
IwGxSetFarZNearZ(); // sets clipping planes
于 2013-10-01T16:56:31.177 回答