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struct Vec3 {
    float x, y, z;
    Vec3(float x=0, float y=0, float z=0) : x(x), y(y), z(z) {}
    Vec3 operator+(const Vec3& v) const { return Vec3(x+v.x, y+v.y, z+v.z); }
    Vec3 operator*(float f) const { return Vec3(x*f, y*f, z*f); }
};

struct Color {
    unsigned char r, g, b;
    Color(unsigned char r=0, unsigned char g=0, unsigned char b=0) : r(r), g(g), b(b) {}
};

class FrameBuffer {
public:
    int width, height;
    std::vector<Color> buffer;
<pre class='brush:php;toolbar:false;'>FrameBuffer(int w, int h) : width(w), height(h), buffer(w * h, Color(0,0,0)) {}

void setPixel(int x, int y, const Color& c) {
    if (x >= 0 && x < width && y >= 0 && y < height) {
        buffer[y * width + x] = c;
    }
}

void s*ePPM(const std::string& filename) {
    std::ofstream out(filename);
    out << "P3\n" << width << " " << height << "\n255\n";
    for (int i = 0; i < width * height; ++i) {
        out << (int)buffer[i].r << " "
            << (int)buffer[i].g << " "
            << (int)buffer[i].b << "\n";
    }
}

};

void drawTriangle(FrameBuffer& fb, Vec3 v0, Vec3 v1, Vec3 v2, const Color& c) {
    // 投影到屏幕：只取x,y，忽略z（正交投影示例）
    int x0 = (int)(v0.x + fb.width/2);
    int y0 = (int)(v0.y + fb.height/2);
    int x1 = (int)(v1.x + fb.width/2);
    int y1 = (int)(v1.y + fb.height/2);
    int x2 = (int)(v2.x + fb.width/2);
    int y2 = (int)(v2.y + fb.height/2);
<pre class='brush:php;toolbar:false;'>// 使用Bresenham画三条边
auto drawLine = [&](int x0, int y0, int x1, int y1) {
    int dx = abs(x1 - x0), sx = x0 < x1 ? 1 : -1;
    int dy = -abs(y1 - y0), sy = y0 < y1 ? 1 : -1;
    int err = dx + dy;

    while (true) {
        fb.setPixel(x0, y0, c);
        if (x0 == x1 && y0 == y1) break;
        int e2 = 2 * err;
        if (e2 >= dy) { err += dy; x0 += sx; }
        if (e2 <= dx) { err += dx; y0 += sy; }
    }
};

drawLine(x0, y0, x1, y1);
drawLine(x1, y1, x2, y2);
drawLine(x2, y2, x0, y0);

}

Vec3 project(Vec3 v, float fov = 250.0f, float zNear = 1.0f) {
    float z = v.z + 5.0f;  // 摄像机在z=-5，物体在原点附近
    if (z < zNear) z = zNear;
    float scale = fov / z;
    return Vec3(v.x * scale, v.y * scale, z);
}

int main() {
    FrameBuffer fb(800, 600);
<pre class='brush:php;toolbar:false;'>// 定义立方体顶点（单位立方体）
Vec3 verts[8] = {
    {-1,-1,-1}, {1,-1,-1}, {1,1,-1}, {-1,1,-1},
    {-1,-1,1},  {1,-1,1},  {1,1,1},  {-1,1,1}
};

// 定义面（每两个三角形组成一个面）
int faces[12][3] = {
    {0,1,2}, {0,2,3},  // 前
    {4,5,6}, {4,6,7},  // 后
    {0,1,5}, {0,5,4},  // 下
    {2,3,7}, {2,7,6},  // 上
    {0,3,7}, {0,7,4},  // 左
    {1,2,6}, {1,6,5}   // 右
};

float angle = 1.0f;  // 旋转角度

for (int i = 0; i < 8; ++i) {
    // 绕y轴旋转
    float x = verts[i].x;
    float z = verts[i].z;
    verts[i].x = x * cos(angle) - z * sin(angle);
    verts[i].z = x * sin(angle) + z * cos(angle);
}

for (int i = 0; i < 12; ++i) {
    Vec3 v0 = project(verts[faces[i][0]]);
    Vec3 v1 = project(verts[faces[i][1]]);
    Vec3 v2 = project(verts[faces[i][2]]);
    drawTriangle(fb, v0, v1, v2, Color(255,255,255));
}

fb.s*ePPM("output.ppm");
return 0;

}