RayTracer/src/scene/BVH.cpp

#include "BVH.h"
#include <list>

void BVH::addModel(PModel model) { models.push_back(std::move(model)); }

void BVH::addModels(std::vector<PModel> _models)
{
    for (int i = 0; i < _models.size(); ++i)
    {
        models.push_back(std::move(_models[i]));
    }
}

void BVH::generate()
{
    std::vector<PNode> pendingNodes;
    while (!models.empty())
    {
        pendingNodes.push_back(std::make_unique<Node>(std::move(models.back())));
        models.pop_back();
    }
    while (pendingNodes.size() > 1)
    {
        int lhs = pendingNodes.size();
        int rhs = pendingNodes.size();
        float minSurface = std::numeric_limits<float>::max();
        for (int i = 0; i < pendingNodes.size(); ++i)
        {
            for (int j = 0; j < pendingNodes.size(); ++j)
            {
                if (i == j)
                    continue;
                AABB combined = AABB::combine(pendingNodes[i]->aabb, pendingNodes[j]->aabb);
                float surface = combined.surfaceArea();
                if (minSurface > surface)
                {
                    lhs = i;
                    rhs = j;
                    minSurface = surface;
                }
            }
        }
        PNode newNode = std::make_unique<Node>(AABB::combine(pendingNodes[lhs]->aabb, pendingNodes[rhs]->aabb));
        newNode->left = std::move(pendingNodes[lhs]);
        newNode->right = std::move(pendingNodes[rhs]);
        pendingNodes.erase(pendingNodes.begin() + lhs);
        pendingNodes.erase(pendingNodes.begin() + rhs);
        pendingNodes.push_back(std::move(newNode));
    }
    hierarchy = std::move(pendingNodes[0]);
}