Octree.h

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#pragma once
 
#include "../PhysicsBody.h"
#include "NodeIndex.h"
#include <glm/glm.hpp>
#include <vector>
#include <cstdint>
 
struct Octant {
    std::uint8_t val; // 0-7 representing the octant
 
    static constexpr std::uint8_t X_MASK = 1 << 0;
    static constexpr std::uint8_t Y_MASK = 1 << 1;
    static constexpr std::uint8_t Z_MASK = 1 << 2;
};
 
struct OctreeNode {
    glm::vec3 center;
    float halfSize;
    NodeIndex children[8];
    uint8_t childMask = 0; // Bitmask to track which children exist
 
    // Leaf nodes only
    std::vector<Physics::PhysicsBody*> bodies;
 
    // Aggregated properties (center, mass)
    glm::vec3 massCenter;
    double totalMass = 0.0;
 
    // Aggregated thermal properties
    double totalEffectiveArea = 0.0; // sum of (epsilon * Area)
    double totalEmission = 0.0;      // sum of (epsilon * Area * T^4)
 
    bool isLeaf() const {
        return childMask == 0;
    }
};
 
class Octree {
private:
    std::vector<OctreeNode> nodes;
    void clear();
    NodeIndex allocateNode(const glm::vec3& center, float halfSize);
    void insert(NodeIndex nodeIndex, Physics::PhysicsBody* body);
    Octant getOctant(NodeIndex nodeIdx, const glm::vec3& pos) const;
public:
    Octree() = default;
    glm::vec3 computeForce(Physics::PhysicsBody* body, double G);
    double computeHeat(Physics::PhysicsBody* body);
    void build(const std::vector<Physics::PhysicsBody*>& bodies);
};