线性代数：Matrix2x2和Matrix3x3

      今天整理自己的框架代码，将Matrix2x2和Matrix3x3给扩展了一下，发现网上unity数学计算相关挺少的，所以记录一下。
      首先扩展Matrix2x2：

using System.Collections;
using System.Collections.Generic;
using Unity.Mathematics;
using UnityEngine;

public class Matrix2x2
{
    #region ///properties

    public const int ROW = 2;
    public const int COLUMN = 2;

    public float M00
    {
        get { return dataArr[0, 0]; }
        set { dataArr[0, 0] = value; }
    }

    public float M01
    {
        get { return dataArr[0, 1]; }
        set { dataArr[0, 1] = value; }
    }

    public float M10
    {
        get { return dataArr[1, 0]; }
        set { dataArr[1, 0] = value; }
    }

    public float M11
    {
        get { return dataArr[1, 1]; }
        set { dataArr[1, 1] = value; }
    }

    private float[,] dataArr = new float[ROW, COLUMN];

    public Vector2 Row0 { get { return new Vector2(M00, M01); } }
    public Vector2 Row1 { get { return new Vector2(M10, M11); } }
    public Vector2 Column0 { get { return new Vector2(M00, M10); } }
    public Vector2 Column1 { get { return new Vector2(M01, M11); } }
    #endregion

    public float this[int row, int col]
    {
        get { return dataArr[row, col]; }
        set { dataArr[row, col] = value; }
    }

    public Matrix2x2() { }

    public Matrix2x2(float m00, float m01, float m10, float m11)
    {
        M00 = m00;
        M01 = m01;

        M10 = m10;
        M11 = m11;
    }
    /// <summary>
    /// xy基向量
    /// 竖向排列
    /// </summary>
    /// <param name="ax"></param>
    /// <param name="ay"></param>
    public Matrix2x2(Vector2 ax, Vector2 ay)
    {
        M00 = ax.x;
        M10 = ax.y;

        M10 = ay.x;
        M11 = ay.y;
    }
    /// <summary>
    /// 2*2数组
    /// </summary>
    /// <param name="arr"></param>
    public Matrix2x2(float[,] arr)
    {
        M00 = arr[0, 0];
        M01 = arr[0, 1];

        M10 = arr[1, 0];
        M11 = arr[1, 1];
    }
    /// <summary>
    /// 矩阵*vector2
    /// </summary>
    /// <param name="m2x2"></param>
    /// <param name="v2"></param>
    /// <returns></returns>
    public static Vector2 operator *(Matrix2x2 m2x2, Vector2 v2)
    {
        float x = Vector2.Dot(m2x2.Row0, v2);
        float y = Vector2.Dot(m2x2.Row1, v2);
        return new Vector2(x, y);
    }
    /// <summary>
    /// 矩阵*矩阵
    /// </summary>
    /// <param name="m2x2a"></param>
    /// <param name="m2x2b"></param>
    /// <returns></returns>
    public static Matrix2x2 operator *(Matrix2x2 m2x2a, Matrix2x2 m2x2b)
    {
        float c00 = Vector2.Dot(m2x2a.Row0, m2x2b.Column0);
        float c01 = Vector2.Dot(m2x2a.Row0, m2x2b.Column1);

        float c10 = Vector2.Dot(m2x2a.Row1, m2x2b.Column0);
        float c11 = Vector2.Dot(m2x2a.Row1, m2x2b.Column1);

        Matrix2x2 ret = new Matrix2x2(c00, c01, c10, c11);
        return ret;
    }
    /// <summary>
    /// 矩阵/标量
    /// </summary>
    /// <param name="m2x2"></param>
    /// <param name="f"></param>
    /// <returns></returns>
    public static Matrix2x2 operator /(Matrix2x2 m2x2, float f)
    {
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                m2x2[x, y] /= f;
            }
        }
        return m2x2;
    }
    /// <summary>
    /// 行列式
    /// </summary>
    /// <returns></returns>
    public float GetDeterminant()
    {
        float det = M00 * M11 - M01 * M10;
        return det;
    }
    /// <summary>
    /// 求转置矩阵
    /// </summary>
    /// <returns></returns>
    public Matrix2x2 GetTransposeMatrix()
    {
        Matrix2x2 m2x2T = new Matrix2x2();
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                m2x2T[x, y] = this[y, x];
            }
        }
        return m2x2T;
    }
    /// <summary>
    /// 求余子式标量
    /// </summary>
    /// <param name="r"></param>
    /// <param name="c"></param>
    /// <returns></returns>
    public float GetCofactorScalar(int r, int c)
    {
        float cof = 0f;
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                if (x != r && y != c)
                {
                    cof = dataArr[x, y];
                    break;
                }
            }
        }
        return cof;
    }
    /// <summary>
    /// 求余子式标量矩阵
    /// + -
    /// - +
    /// </summary>
    /// <returns></returns>
    public Matrix2x2 GetCofactorScalarMatrix()
    {
        Matrix2x2 m2x2 = new Matrix2x2();
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                float cof = GetCofactorScalar(x, y);
                bool ispostive = (x + y) % 2 == 0;
                m2x2[x, y] = ispostive ? cof : -cof;
            }
        }
        return m2x2;
    }
    /// <summary>
    /// 求伴随矩阵
    /// 算法：余子式标量矩阵的转置
    /// </summary>
    /// <returns></returns>
    public Matrix2x2 GetAdjointMatrix()
    {
        Matrix2x2 m2x2 = GetCofactorScalarMatrix();
        Matrix2x2 m2x2T = m2x2.GetTransposeMatrix();
        return m2x2T;
    }
    /// <summary>
    /// 求逆矩阵
    /// 算法：伴随矩阵/行列式值
    /// </summary>
    /// <returns></returns>
    public Matrix2x2 GetInverseMatrix()
    {
        Matrix2x2 m2x2 = GetAdjointMatrix();
        float det = GetDeterminant();
        Matrix2x2 m2x2I = m2x2 / det;
        return m2x2I;
    }

    public override string ToString()
    {
        string ret = $"换行\nM00:{M00} M01:{M01} \nM10:{M10} M11:{M11}";
        return ret;
    }
}

      关于Matrix2x2，我设计了构造、转置、余子式（2x2矩阵的余子式为标量，或称1x1矩阵）、余子式标量矩阵、伴随矩阵和逆矩阵。
      基本上数学运算开发够用了，每个函数的意义只在代码注释上简单说明。
      这里只举一个例子：逆矩阵可以将矩阵变换后向量再变换回来，比如：

Matrix2x2 m2x2 = new Matrix2x2();
m2x2.M00 = 0.3f;
m2x2.M01 = 1.2f;
m2x2.M10 = 5.2f;
m2x2.M11 = -1f;

Debug.LogErrorFormat($"m2x2 = {m2x2}");

Vector2 vec0 = new Vector2(5.8f, 56.1f);

Vector2 vec1 = m2x2 * vec0;

Matrix2x2 m2x2I = m2x2.GetInverseMatrix();

Debug.LogErrorFormat($"m2x2I = {m2x2I}");

Vector2 vec2 = m2x2I * vec1;

Debug.LogErrorFormat($"vec0 = {vec0} vec1 = {vec1} vec2 = {vec2}");

      结果：

      接下来扩展Matrix3x3：

using NPOI.SS.Formula.Functions;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[System.Serializable]
public class Matrix3x3
{
    #region ///properties

    public const int ROW = 3;
    public const int COLUMN = 3;

    public float M00
    {
        get { return dataArr[0, 0]; }
        set { dataArr[0, 0] = value; }
    }

    public float M01
    {
        get { return dataArr[0, 1]; }
        set { dataArr[0, 1] = value; }
    }

    public float M02
    {
        get { return dataArr[0, 2]; }
        set { dataArr[0, 2] = value; }
    }

    public float M10
    {
        get { return dataArr[1, 0]; }
        set { dataArr[1, 0] = value; }
    }

    public float M11
    {
        get { return dataArr[1, 1]; }
        set { dataArr[1, 1] = value; }
    }

    public float M12
    {
        get { return dataArr[1, 2]; }
        set { dataArr[1, 2] = value; }
    }

    public float M20
    {
        get { return dataArr[2, 0]; }
        set { dataArr[2, 0] = value; }
    }

    public float M21
    {
        get { return dataArr[2, 1]; }
        set { dataArr[2, 1] = value; }
    }

    public float M22
    {
        get { return dataArr[2, 2]; }
        set { dataArr[2, 2] = value; }
    }

    public float[,] dataArr = new float[ROW, COLUMN];

    public Vector3 Row0 { get { return new Vector3(M00, M01, M02); } }
    public Vector3 Row1 { get { return new Vector3(M10, M11, M12); } }
    public Vector3 Row2 { get { return new Vector3(M20, M21, M22); } }
    public Vector3 Column0 { get { return new Vector3(M00, M10, M20); } }
    public Vector3 Column1 { get { return new Vector3(M01, M11, M21); } }
    public Vector3 Column2 { get { return new Vector3(M02, M12, M22); } }
    #endregion

    public float this[int row, int col]
    {
        get { return dataArr[row, col]; }
        set { dataArr[row, col] = value; }
    }

    public Matrix3x3() { }

    public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
    {
        M00 = m00;
        M01 = m01;
        M02 = m02;

        M10 = m10;
        M11 = m11;
        M12 = m12;

        M20 = m20;
        M21 = m21;
        M22 = m22;
    }
    /// <summary>
    /// xyz基向量排列
    /// </summary>
    /// <param name="ax">x基向量</param>
    /// <param name="ay">y基向量</param>
    /// <param name="az">z基向量</param>
    public Matrix3x3(Vector3 ax, Vector3 ay, Vector3 az)
    {
        M00 = ax.x;
        M10 = ax.y;
        M20 = ax.z;

        M01 = ay.x;
        M11 = ay.y;
        M21 = ay.z;

        M02 = az.x;
        M12 = az.y;
        M22 = az.z;
    }
    /// <summary>
    /// 数组排列
    /// </summary>
    /// <param name="arr"></param>
    public Matrix3x3(float[,] arr)
    {
        M00 = arr[0, 0];
        M01 = arr[0, 1];
        M02 = arr[0, 2];

        M10 = arr[1, 0];
        M11 = arr[1, 1];
        M12 = arr[1, 2];

        M20 = arr[2, 0];
        M21 = arr[2, 1];
        M22 = arr[2, 2];
    }
    /// <summary>
    /// 矩阵*vector2
    /// </summary>
    /// <param name="m3x3"></param>
    /// <param name="v2"></param>
    /// <returns></returns>
    public static Vector2 operator *(Matrix3x3 m3x3, Vector2 v2)
    {
        Vector3 v3 = new Vector3(v2.x, v2.y, 1);
        v3 = m3x3 * v3;
        v2 = new Vector2(v3.x, v3.y);
        return v2;
    }
    /// <summary>
    /// 矩阵*vector3
    /// </summary>
    /// <param name="m3x3"></param>
    /// <param name="v3"></param>
    /// <returns></returns>
    public static Vector3 operator *(Matrix3x3 m3x3, Vector3 v3)
    {
        float x = Vector3.Dot(m3x3.Row0, v3);
        float y = Vector3.Dot(m3x3.Row1, v3);
        float z = Vector3.Dot(m3x3.Row2, v3);

        return new Vector3(x, y, z);
    }
    /// <summary>
    /// 矩阵*矩阵
    /// </summary>
    /// <param name="m3x3a"></param>
    /// <param name="m3x3b"></param>
    /// <returns></returns>
    public static Matrix3x3 operator *(Matrix3x3 m3x3a, Matrix3x3 m3x3b)
    {
        float c00 = Vector2.Dot(m3x3a.Row0, m3x3b.Column0);
        float c01 = Vector2.Dot(m3x3a.Row0, m3x3b.Column1);
        float c02 = Vector2.Dot(m3x3a.Row0, m3x3b.Column2);

        float c10 = Vector2.Dot(m3x3a.Row1, m3x3b.Column0);
        float c11 = Vector2.Dot(m3x3a.Row1, m3x3b.Column1);
        float c12 = Vector2.Dot(m3x3a.Row1, m3x3b.Column2);

        float c20 = Vector2.Dot(m3x3a.Row2, m3x3b.Column0);
        float c21 = Vector2.Dot(m3x3a.Row2, m3x3b.Column1);
        float c22 = Vector2.Dot(m3x3a.Row2, m3x3b.Column2);

        Matrix3x3 ret = new Matrix3x3(c00, c01, c02, c10, c11, c12, c20, c21, c22);
        return ret;
    }
    /// <summary>
    /// 矩阵/标量
    /// </summary>
    /// <param name="m3x3"></param>
    /// <param name="f"></param>
    /// <returns></returns>
    public static Matrix3x3 operator /(Matrix3x3 m3x3, float f)
    {
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                m3x3[x, y] /= f;
            }
        }
        return m3x3;
    }
    /// <summary>
    /// 求行列式
    /// </summary>
    /// <returns></returns>
    public float GetDeterminant()
    {
        float det = M00 * M11 * M22 + M01 * M12 * M20 + M02 * M10 * M21 - M02 * M11 * M20 - M01 * M10 * M22 - M00 * M12 * M21;
        return det;
    }
    /// <summary>
    /// 求转置矩阵
    /// </summary>
    /// <returns></returns>
    public Matrix3x3 GetTransposeMatrix()
    {
        Matrix3x3 m3x3T = new Matrix3x3();
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                m3x3T[x, y] = this[y, x];
            }
        }
        return m3x3T;
    }
    /// <summary>
    /// 求余子式矩阵
    /// </summary>
    /// <param name="r"></param>
    /// <param name="c"></param>
    /// <returns></returns>
    public Matrix2x2 GetCofactorMatrix(int r, int c)
    {
        Matrix2x2 m2x2 = new Matrix2x2();
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                if (x != r && y != c)
                {
                    int row = x > r ? x - 1 : x;
                    int col = y > c ? y - 1 : y;
                    m2x2[row, col] = this[x, y];
                }
            }
        }
        return m2x2;
    }
    /// <summary>
    /// 求代数余子式（余子式矩阵的行列式）矩阵
    /// 余子式矩阵行列式正负号
    /// + - +
    /// - + -
    /// + - +
    /// </summary>
    /// <returns></returns>
    public Matrix3x3 GetCofactorDeterminantMatrix()
    {
        Matrix3x3 m3x3 = new Matrix3x3();
        for (int x = 0; x < ROW; x++)
        {
            for (int y = 0; y < COLUMN; y++)
            {
                Matrix2x2 m2x2 = GetCofactorMatrix(x, y);
                float m2x2det = m2x2.GetDeterminant();
                bool ispostive = (x + y) % 2 == 0;
                m3x3[x, y] = ispostive ? m2x2det : -m2x2det;
            }
        }
        return m3x3;
    }
    /// <summary>
    /// 求伴随矩阵
    /// 算法：代数余子式矩阵的转置
    /// </summary>
    /// <returns></returns>
    public Matrix3x3 GetAdjointMatrix()
    {
        Matrix3x3 m3x3 = GetCofactorDeterminantMatrix();
        Matrix3x3 m3x3T = m3x3.GetTransposeMatrix();
        return m3x3T;
    }
    /// <summary>
    /// 求逆矩阵
    /// 算法：伴随矩阵/行列式值
    /// </summary>
    /// <returns></returns>
    public Matrix3x3 GetInverseMatrix()
    {
        Matrix3x3 m3x3 = GetAdjointMatrix();
        float det = GetDeterminant();
        Matrix3x3 m3x3I = m3x3 / det;
        return m3x3I;
    }

    public override string ToString()
    {
        string ret = $"换行\nM00:{M00} M01:{M01} M02:{M02} \nM10:{M10} M11:{M11} M12:{M12} \nM20:{M20} M21:{M21} M12:{M22}";
        return ret;
    }
}

      还是用逆矩阵验证一下：

Matrix3x3 m3x3 = new Matrix3x3();
m3x3.M00 = -0.3f;
m3x3.M01 = 6.2f;
m3x3.M02 = 12.6f;
m3x3.M10 = 5.2f;
m3x3.M11 = -1.8f;
m3x3.M12 = 7.8f;
m3x3.M20 = -52.2f;
m3x3.M21 = 6.4f;
m3x3.M22 = -70.1f;

Debug.LogErrorFormat($"m3x3 = {m3x3}");

Vector3 vec0 = new Vector3(20.3f, -54f, 4.4f);

Vector3 vec1 = m3x3 * vec0;

Matrix3x3 m3x3I = m3x3.GetInverseMatrix();

Debug.LogErrorFormat($"m3x3I = {m3x3I}");

Vector3 vec2 = m3x3I * vec1;

Debug.LogErrorFormat($"vec0 = {vec0} vec1 = {vec1} vec2 = {vec2}");

      结果：

      OK，洗了睡，这里吐槽一下：这些矩阵计算unity应该直接提供，写起来眼睛都要看瞎了。