10,000 Trees and Bullets Without Blowing Up RAM

#include <cstdint>
#include <print>
#include <string>
#include <vector>

// Naive Tree: every instance duplicates heavy texture and vertex buffer data.
class NaiveTree {
    float x_;
    float y_;
    float scale_;
    std::string species_;
    std::string textureId_;
    std::vector<float> meshVertices_; // 3D/2D vertex buffer (e.g., 256 floats per tree)

public:
    NaiveTree(float x, float y, float scale, std::string species, std::string textureId,
              std::vector<float> vertices)
        : x_(x), y_(y), scale_(scale), species_(std::move(species)),
          textureId_(std::move(textureId)), meshVertices_(std::move(vertices)) {}

    void render() const {
        std::println("Rendering {} at ({:.1f}, {:.1f}) scale {:.1f} with {} vertices [tex: {}]",
                     species_, x_, y_, scale_, meshVertices_.size(), textureId_);
    }

    [[nodiscard]] size_t bytesUsed() const {
        return sizeof(*this) + species_.capacity() + textureId_.capacity() +
               (meshVertices_.capacity() * sizeof(float));
    }
};

int main() {
    // A single tree mesh of 256 floats (~1 KB buffer)
    std::vector<float> sampleMesh(256, 1.0f);

    std::vector<NaiveTree> forest;
    forest.reserve(10000);

    // Spawning 10,000 trees copies the heavy vertex vector and strings 10,000 times!
    for (int i = 0; i < 10000; ++i) {
        std::string species = (i % 3 == 0) ? "Oak" : (i % 3 == 1) ? "Pine" : "CherryBlossom";
        std::string texture = "tex_" + species + "_diffuse.png";
        forest.emplace_back(static_cast<float>(i % 100), static_cast<float>(i / 100), 1.0f,
                            species, texture, sampleMesh);
    }

    size_t totalBytes = 0;
    for (const auto& tree : forest) {
        totalBytes += tree.bytesUsed();
    }

    std::println("Spawned {} naive trees.", forest.size());
    std::println("Total RAM used by naive trees: {:.2f} MB", static_cast<double>(totalBytes) / (1024.0 * 1024.0));
    std::println("Sample tree render:");
    forest[0].render();
    forest[1].render();

    return 0;
}