矩阵相乘

1. 矩阵和矩阵相乘

2. 矩阵和向量相乘

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication6
{
    class Program
    {
        static void Main(string[] args)
        {

            Vector3 c = new Vector3(1, 2, 3);

            Matrix3x3 x1 = new Matrix3x3() 
            {
                m11 = 1,m12 = -5,m13 = 3,
                m21 = 0,m22 = -2,m23 = 6,
                m31 = 7,m32 = 2,m33 = -4
            };

            Matrix3x3 x2 = new Matrix3x3()
            {
                m11 = -8,
                m12 = 6,
                m13 = 1,
                m21 = 7,
                m22 = 0,
                m23 = -3,
                m31 = 2,
                m32 = 4,
                m33 = 5
            };

            c = c * x1;
            Console.WriteLine(x1 * x2);
            Console.WriteLine("");
            Console.WriteLine(c);

            Console.ReadLine();
        }
    }

    class Matrix3x3 
    {
        public float m11, m12, m13;
        public float m21, m22, m23;
        public float m31, m32, m33;


        public Matrix3x3(){}

        public Matrix3x3(
            float m11,float m12,float m13,
            float m21,float m22,float m23,
            float m31,float m32,float m33) 
        {
            this.m11 = m11;
            this.m12 = m12;
            this.m13 = m13;
            this.m21 = m21;
            this.m22 = m22;
            this.m23 = m23;
            this.m31 = m31;
            this.m32 = m32;
            this.m33 = m33;
        }

        //矩阵相乘
        public static Matrix3x3 operator *(Matrix3x3 a,Matrix3x3 b)
        {
            Matrix3x3 r = new Matrix3x3();
            
            r.m11 = a.m11 * b.m11 + a.m12 * b.m21 + a.m13 * b.m31;
            r.m12 = a.m11 * b.m12 + a.m12 * b.m22 + a.m13 * b.m32;
            r.m13 = a.m11 * b.m13 + a.m12 * b.m23 + a.m13 * b.m33;

            r.m21 = a.m21 * b.m11 + a.m22 * b.m21 + a.m23 * b.m31;
            r.m22 = a.m21 * b.m12 + a.m22 * b.m22 + a.m23 * b.m32;
            r.m23 = a.m21 * b.m13 + a.m22 * b.m23 + a.m23 * b.m33;

            r.m31 = a.m31 * b.m11 + a.m32 * b.m21 + a.m33 * b.m31;
            r.m32 = a.m31 * b.m12 + a.m32 * b.m22 + a.m33 * b.m32;
            r.m33 = a.m31 * b.m13 + a.m32 * b.m23 + a.m33 * b.m33;

            return r;
        }

        //向量乘以矩阵(行向量)vABC
        public static Vector3 operator *(Vector3 a, Matrix3x3 b) 
        {
            return new Vector3
                (
                    a.x * b.m11 + a.y * b.m21 + a.z * b.m31,
                    a.x * b.m12 + a.y * b.m22 + a.z * b.m32,
                    a.x * b.m13 + a.y * b.m23 + a.z * b.m33
                );
        }


        public override string ToString()
        {
            return string.Format("{0} {1} {2}\r\n{3} {4} {5}\r\n{6} {7} {8}\r\n"
                    , m11, m12, m13, m21, m22, m23, m31, m32, m33);
        }

    }

    class Vector3 
    {
        public float x, y, z;

        public Vector3(float x,float y,float z) 
        {
            this.x = x;
            this.y = y;
            this.z = z;
        }

        public override string ToString()
        {
            return string.Format("{0} {1} {2}", x, y, z);
        }
    }
                                                                
}