[collision-solver] Avoid unnecessary memory allocations

Author: IAmNotHanni

include/inexor/vulkan-renderer/world/collision_solver.hpp

@@ -16,44 +16,42 @@ namespace inexor::vulkan_renderer::world {
 
 class OctreeCollisionSolver {
 private:
-    std::vector<std::pair<std::shared_ptr<world::Cube>, float>> m_collision_candidates{};
+    const std::vector<std::shared_ptr<world::Cube>> m_worlds;
+    std::vector<std::pair<std::shared_ptr<world::Cube>, float>> m_collision_candidates;
     std::shared_mutex m_collision_solver_mutex;
 
     /// @brief Find all collisions between the given ray and the given octrees, sorted by increasing distance between
     /// the octree and the camera.
-    /// @param worlds The octrees to check for collision
     /// @param position The start position of the ray
     /// @param direction The direction vector of the ray
     /// @return A vector of the found collisions. If no collisions were found, the vector is empty.
     [[nodiscard]] std::vector<RayCubeCollision<Cube>>
-    find_all_ray_octree_collisions(const std::vector<std::shared_ptr<world::Cube>> &worlds, glm::vec3 position,
-                                   glm::vec3 direction, bool find_only_one_collision = true);
+    find_all_ray_octree_collisions(glm::vec3 position, glm::vec3 direction, bool find_only_one_collision = true);
 
 public:
+    /// @brief Default constructor
+    /// @param worlds The octree worlds to test collision with
+    explicit OctreeCollisionSolver(const std::vector<std::shared_ptr<world::Cube>> &worlds);
 
     // TODO: Implement min/max collision distance if required.
     // TODO: Start sorting octrees by distance to camera only after a certain number of worlds.
     // TODO: Implement a bounding volume hierarchy (BVH) tree, for example an octree for all the octrees.
 
     /// @brief Find a collision between a ray and an octree which is closest to the camera.
-    /// @param worlds The octrees to check for collision
     /// @param position The start position of the ray
     /// @param direction The direction vector of the ray
     /// @return The collision data
-    [[nodiscard]] std::optional<RayCubeCollision<Cube>>
-    find_ray_octree_collision(const std::vector<std::shared_ptr<world::Cube>> &worlds, glm::vec3 position,
-                              glm::vec3 direction);
+    [[nodiscard]] std::optional<RayCubeCollision<Cube>> find_ray_octree_collision(glm::vec3 position,
+                                                                                  glm::vec3 direction);
 
     /// @brief Find all collisions between the given ray and the given octrees, sorted by increasing distance between
     /// the octree and the camera.
     /// @note Expect this method to be more costly than find_ray_octree_collision!
-    /// @param worlds The octrees to check for collision
     /// @param position The start position of the ray
     /// @param direction The direction vector of the ray
     /// @return A vector of the found collisions. If no collisions were found, the vector is empty.
-    [[nodiscard]] std::vector<RayCubeCollision<Cube>>
-    find_all_ray_octree_collisions(const std::vector<std::shared_ptr<world::Cube>> &worlds, glm::vec3 position,
-                                   glm::vec3 direction);
+    [[nodiscard]] std::vector<RayCubeCollision<Cube>> find_all_ray_octree_collisions(glm::vec3 position,
+                                                                                     glm::vec3 direction);
 };
 
 } // namespace inexor::vulkan_renderer::world

src/vulkan-renderer/application.cpp

@@ -184,7 +184,7 @@ void Application::load_octree_geometry() {
     m_worlds.emplace_back(std::make_shared<world::Cube>(1.0f, glm::vec3{0, 0, 0}));
     m_worlds.emplace_back(std::make_shared<world::Cube>(1.6f, glm::vec3{0, 10, 0}));
 
-    m_collision_solver = std::make_unique<world::OctreeCollisionSolver>();
+    m_collision_solver = std::make_unique<world::OctreeCollisionSolver>(m_worlds);
 
     m_worlds[0]->set_type(world::Cube::Type::OCTANT);
     m_worlds[1]->set_type(world::Cube::Type::SOLID);
@@ -576,8 +576,7 @@ void Application::check_octree_collisions() {
     // TODO: Apply one big global octree for bounding volume hierarchy.
     // TODO: Implement a world manager which resolves multiple octree collision.
 
-    const auto collision =
-        m_collision_solver->find_ray_octree_collision(m_worlds, m_camera->position(), m_camera->front());
+    const auto collision = m_collision_solver->find_ray_octree_collision(m_camera->position(), m_camera->front());
 
     if (collision) {
         const auto cube_hit = collision.value().cube_intersection();

src/vulkan-renderer/world/collision_solver.cpp

@@ -9,27 +9,29 @@
 
 namespace inexor::vulkan_renderer::world {
 
+OctreeCollisionSolver::OctreeCollisionSolver(const std::vector<std::shared_ptr<world::Cube>> &worlds)
+    : m_worlds(worlds) {
+    assert(!worlds.empty());
+    std::scoped_lock lock(m_collision_solver_mutex);
+    m_collision_candidates.reserve(worlds.size());
+}
+
 std::vector<RayCubeCollision<Cube>>
-OctreeCollisionSolver::find_all_ray_octree_collisions(const std::vector<std::shared_ptr<world::Cube>> &worlds,
-                                                      const glm::vec3 position, const glm::vec3 direction,
+OctreeCollisionSolver::find_all_ray_octree_collisions(const glm::vec3 position, const glm::vec3 direction,
                                                       bool find_only_one_collision) {
-    if (worlds.empty()) {
-        return {};
-    }
-
     std::vector<RayCubeCollision<Cube>> found_collisions;
 
-    found_collisions.reserve(worlds.size());
+    found_collisions.reserve(m_worlds.size());
 
     // We need a critical section because we are modifying m_collision_candidates.
     {
         std::scoped_lock lock(m_collision_solver_mutex);
 
-        // TODO: Optimize this! Avoid memory re-allocation if possible and benchmark it.
+        // We must delete the entry from previous calls of this method so we can call emplace_back.
+        // This will not change the capacity of the vector which was set in the constructor.
         m_collision_candidates.clear();
-        m_collision_candidates.reserve(worlds.size());
 
-        for (const auto &world : worlds) {
+        for (const auto &world : m_worlds) {
             if (is_bounding_box_and_bounding_sphere_hit(world, position, direction)) {
                 m_collision_candidates.emplace_back(std::make_pair(world, glm::distance2(position, direction)));
             }
@@ -60,10 +62,9 @@ OctreeCollisionSolver::find_all_ray_octree_collisions(const std::vector<std::sha
     return std::move(found_collisions);
 }
 
-std::optional<RayCubeCollision<Cube>>
-OctreeCollisionSolver::find_ray_octree_collision(const std::vector<std::shared_ptr<world::Cube>> &worlds,
-                                                 const glm::vec3 position, const glm::vec3 direction) {
-    const auto result = find_all_ray_octree_collisions(worlds, position, direction, true);
+std::optional<RayCubeCollision<Cube>> OctreeCollisionSolver::find_ray_octree_collision(const glm::vec3 position,
+                                                                                       const glm::vec3 direction) {
+    const auto result = find_all_ray_octree_collisions(position, direction, true);
 
     if (!result.empty()) {
         return result[0];
@@ -72,10 +73,9 @@ OctreeCollisionSolver::find_ray_octree_collision(const std::vector<std::shared_p
     return std::nullopt;
 }
 
-std::vector<RayCubeCollision<Cube>>
-OctreeCollisionSolver::find_all_ray_octree_collisions(const std::vector<std::shared_ptr<world::Cube>> &worlds,
-                                                      const glm::vec3 position, const glm::vec3 direction) {
-    return find_all_ray_octree_collisions(worlds, position, direction, false);
+std::vector<RayCubeCollision<Cube>> OctreeCollisionSolver::find_all_ray_octree_collisions(const glm::vec3 position,
+                                                                                          const glm::vec3 direction) {
+    return find_all_ray_octree_collisions(position, direction, false);
 }
 
 } // namespace inexor::vulkan_renderer::world