STL2Voxel/Geometry.hpp

#pragma once
#include <vector>
#include <cassert>

template<typename T>
class Vec3 {
public:
    Vec3(T a_, T b_, T c_) : a(a_), b(b_), c(c_) {}
    Vec3() : a(0), b(0), c(0) {}

    union { T x, a; };
    union { T y, b; };
    union { T z, c; };

    T operator[](int i) const {
        if (i == 0) {
            return a;
        } else if (i == 1) {
            return b;
        } else if (i == 2) {
            return c;
        }
        return a;
    }

    T &operator[](int i) {
        if (i == 0) {
            return a;
        } else if (i == 1) {
            return b;
        } else if (i == 2) {
            return c;
        }
        return a;
    }

    Vec3 operator+(const Vec3 &other) const {
        return {a + other.a, b + other.b, c + other.c};
    }

    Vec3 operator/(const float w) const {
        return {a / w, b / w, c / w};
    }

    Vec3 operator-(const Vec3 &other) const {
        return {a - other.a, b - other.b, c - other.c};
    }

    Vec3 operator*(const float &w) const {
        return {a * w, b * w, c * w};
    }

    float length() const {
        return sqrt(a * a + b * b + c * c);
    }

    Vec3 norm() const {
        return *this / length();
    }

    Vec3 cross(const Vec3 &other) const {
        return {b * other.c - c * other.b, c * other.a - a * other.c, a * other.b - b * other.a};
    }

    float dot(const Vec3 &other) const {
        return a * other.a + b * other.b + c * other.c;
    }

    bool operator==(const Vec3& other) const {
        return x == other.x && y == other.y && z == other.z;
    }
};

// 为 Vec3 创建哈希函数
namespace std {
    template<typename T>
    struct hash<Vec3<T>> {
    size_t operator()(const Vec3<T>& vec) const {
        return hash<T>()(vec.x) ^ hash<T>()(vec.y) ^ hash<T>()(vec.z);
    }
};
}

typedef Vec3<float> Vec3f;
typedef Vec3<unsigned int> Vec3u;

class AABB {
public:
    Vec3f min = {std::numeric_limits<float>::max(), std::numeric_limits<float>::max(),
                 std::numeric_limits<float>::max()};
    Vec3f max = {std::numeric_limits<float>::lowest(), std::numeric_limits<float>::lowest(),
                 std::numeric_limits<float>::lowest()};
    Vec3f center() const {
        return (min + max) / 2;
    }
    Vec3f size() const {
        return max - min;
    }
    AABB operator+(const Vec3f& v) const {
        return {min + v, max + v};
    }
};

class Mesh {
public:
    std::vector<Vec3f> vertices;
    std::vector<Vec3u> faces;
    // 获得指定面的 AABB
    AABB getAABB(const std::vector<size_t>& faceIndices) const {
        AABB aabb;
        for (const size_t &idx: faceIndices) {
            const Vec3u &face = faces[idx];
            for (int i = 0; i < 3; ++i) {
                const Vec3f &v = vertices[face[i]];
                for (int j = 0; j < 3; ++j) {
                    aabb.min[j] = std::min(aabb.min[j], v[j]);
                    aabb.max[j] = std::max(aabb.max[j], v[j]);
                }
            }
        }
        return aabb;
    }
    AABB getAABB() const {
        AABB aabb;
        for (const Vec3f &v: vertices) {
            for (int j = 0; j < 3; ++j) {
                aabb.min[j] = std::min(aabb.min[j], v[j]);
                aabb.max[j] = std::max(aabb.max[j], v[j]);
            }
        }
        return aabb;
    }
};


//class LineSegment {
//public:
//    Vec3f start;
//    Vec3f end;
//
//    /**
//     * @brief Construct a new Line Segment object
//     * @param s start point
//     * @param e end point
//     * @param r radius
//     */
//    LineSegment(const Vec3f &s, const Vec3f &e, const float r = 0) : start(s), end(e) {
//        length = (end - start).length();
//        dir = (end - start).norm();
//    }
//
//    float getLength() const {
//        return length;
//    }
//
//    Vec3f getDir() const {
//        return dir;
//    }
//
//private:
//    float length;
//    Vec3f dir;
//};

class Ray {
public:
    Vec3f start;
    Vec3f dir;

    Ray(const Vec3f &s, const Vec3f &d) : start(s), dir(d) {
        dir = dir.norm();
    }
};