用c语言写一个三维坐标系的旋转矩阵

以下是用C语言写的三维旋转矩阵代码，可以根据需要修改旋转角度和坐标轴：

#include <stdio.h>
#include <math.h>

#define PI 3.14159265

// 三维向量结构体
typedef struct {
    double x, y, z;
} Vector3;

// 旋转矩阵结构体
typedef struct {
    double m[3][3];
} Matrix3x3;

// 初始化旋转矩阵
Matrix3x3 init_rotation_matrix(double angle, char axis) {
    Matrix3x3 matrix;
    double radian = angle * PI / 180.0;
    double c = cos(radian);
    double s = sin(radian);
    switch (axis) {
        case 'x':
            matrix.m[0][0] = 1.0;
            matrix.m[1][1] = c;
            matrix.m[1][2] = -s;
            matrix.m[2][1] = s;
            matrix.m[2][2] = c;
            break;
        case 'y':
            matrix.m[0][0] = c;
            matrix.m[0][2] = s;
            matrix.m[1][1] = 1.0;
            matrix.m[2][0] = -s;
            matrix.m[2][2] = c;
            break;
        case 'z':
            matrix.m[0][0] = c;
            matrix.m[0][1] = -s;
            matrix.m[1][0] = s;
            matrix.m[1][1] = c;
            matrix.m[2][2] = 1.0;
            break;
        default:
            break;
    }
    return matrix;
}

// 矩阵乘法
Matrix3x3 matrix_multiply(Matrix3x3 a, Matrix3x3 b) {
    Matrix3x3 c;
    int i, j, k;
    for (i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            c.m[i][j] = 0.0;
            for (k = 0; k < 3; k++) {
                c.m[i][j] += a.m[i][k] * b.m[k][j];
            }
        }
    }
    return c;
}

// 旋转向量
Vector3 rotate_vector(Vector3 vector, Matrix3x3 matrix) {
    Vector3 result;
    result.x = matrix.m[0][0] * vector.x + matrix.m[0][1] * vector.y + matrix.m[0][2] * vector.z;
    result.y = matrix.m[1][0] * vector.x + matrix.m[1][1] * vector.y + matrix.m[1][2] * vector.z;
    result.z = matrix.m[2][0] * vector.x + matrix.m[2][1] * vector.y + matrix.m[2][2] * vector.z;
    return result;
}

int main() {
    // 测试代码
    Vector3 vector = {1.0, 0.0, 0.0};
    Matrix3x3 matrix = init_rotation_matrix(45.0, 'z');
    Vector3 result = rotate_vector(vector, matrix);
    printf("result: (%f, %f, %f)\n", result.x, result.y, result.z);
    return 0;
}

该代码中定义了一个三维向量结构体和一个三维旋转矩阵结构体。`init_rotation_matrix`函数用于初始化旋转矩阵，根据旋转角度和坐标轴生成一个旋转矩阵；`matrix_multiply`函数用于矩阵乘法；`rotate_vector`函数用于旋转三维向量。在`main`函数中，我们测试了一个向量绕z轴旋转45度后的结果。