Add Bullet Physics integration.

Author: BurntRanch

Makefile

@@ -23,9 +23,9 @@ NAME		 = BurntEngine
 TARGET		 = libengine.so.1
 SRC 	   	 = $(sort $(wildcard src/*.cpp))
 OBJ 	   	 = $(SRC:.cpp=.o)
-LDFLAGS   	+= -L$(BUILDDIR)/fmt -L$(BUILDDIR)/steam -lGameNetworkingSockets -lassimp -l:libfmt.a -lSDL3 -lvulkan -lfreetype -shared -fno-PIE -Wl,-soname,$(TARGET)
+LDFLAGS   	+= -L$(BUILDDIR)/fmt -L$(BUILDDIR)/steam -lGameNetworkingSockets -lassimp -lBulletSoftBody -lBulletDynamics -lBulletCollision -lLinearMath -l:libfmt.a -lSDL3 -lvulkan -lfreetype -shared -fno-PIE -Wl,-soname,$(TARGET)
 CXXFLAGS  	?= -mtune=generic -march=native
-CXXFLAGS        += -funroll-all-loops -Iinclude -Iinclude/steam -isystem/usr/include/freetype2 -fPIC -std=c++17 $(VARS)
+CXXFLAGS        += -funroll-all-loops -Iinclude -Iinclude/steam -I/usr/include/bullet -isystem/usr/include/freetype2 -std=c++17 -fPIC $(VARS)
 
 all: fmt toml gamenetworkingsockets $(TARGET)
 

compile_flags.txt

@@ -1,3 +1,4 @@
 -Iinclude
 -Iinclude/steam
+-I/usr/include/bullet
 -isystem/usr/include/freetype2

include/engine.hpp

@@ -1,6 +1,11 @@
 #ifndef ENGINE_HPP
 #define ENGINE_HPP
 
+#include <BulletCollision/BroadphaseCollision/btBroadphaseInterface.h>
+#include <BulletCollision/BroadphaseCollision/btDispatcher.h>
+#include <BulletCollision/CollisionDispatch/btCollisionConfiguration.h>
+#include <BulletDynamics/ConstraintSolver/btConstraintSolver.h>
+#include <BulletDynamics/Dynamics/btDiscreteDynamicsWorld.h>
 #include "camera.hpp"
 #include "common.hpp"
 #include "isteamnetworkingsockets.h"
@@ -9,6 +14,9 @@
 #include "ui/button.hpp"
 #include "object.hpp"
 
+#include <LinearMath/btVector3.h>
+#include <btBulletDynamicsCommon.h>
+
 #include <future>
 #include <mutex>
 #include <unordered_map>
@@ -502,6 +510,12 @@ class Engine {
 
     void InitNetworking();
 
+    /* Initializes the Bullet Physics engine, Relies on Networking being enabled. */
+    void InitPhysics();
+
+    /* Stops the physics engine. */
+    void DeinitPhysics();
+
     /* UI::Button listeners will receive events when any button is pressed, along with its ID. */
     /* Due to how it works, this function can be called before the renderer is initialized. */
     void RegisterUIButtonListener(const std::function<void(std::string)> listener);
@@ -560,6 +574,14 @@ class Engine {
     Renderer *m_Renderer = nullptr;
     ISteamNetworkingSockets *m_NetworkingSockets;
 
+    std::unique_ptr<btCollisionConfiguration> m_CollisionConfig;
+    std::unique_ptr<btDispatcher> m_Dispatcher;
+    std::unique_ptr<btBroadphaseInterface> m_Broadphase;
+    std::unique_ptr<btConstraintSolver> m_Solver;
+    std::unique_ptr<btDiscreteDynamicsWorld> m_DynamicsWorld;
+
+    std::vector<std::shared_ptr<btCollisionShape>> m_CollisionShapes;
+
     /* [0] = client, [1] = server. */
     std::array<NetworkingThreadState, 2> m_NetworkingThreadStates;
 
@@ -600,6 +622,8 @@ class Engine {
         m_CallbackInstance->ConnectionStatusChanged(callbackInfo);
     }
 
+    void PhysicsStep(float deltaTime);
+
     /* Do not set isRecursive to true, This is only there to recursively add objs children BEFORE obj. This is a requirement in the protocol.
      * The return is optional (empty if obj is a child and isRecursive == false) but that doesn't mean you have to put it in the statePacket yourself. It's just there incase you want it.
     */

src/engine.cpp

@@ -1,5 +1,15 @@
 #include "engine.hpp"
 
+#include "BulletCollision/BroadphaseCollision/btDbvtBroadphase.h"
+#include "BulletCollision/BroadphaseCollision/btDispatcher.h"
+#include "BulletCollision/CollisionDispatch/btCollisionConfiguration.h"
+#include "BulletCollision/CollisionDispatch/btCollisionObject.h"
+#include "BulletCollision/CollisionDispatch/btDefaultCollisionConfiguration.h"
+#include "BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.h"
+#include "BulletDynamics/Dynamics/btDiscreteDynamicsWorld.h"
+#include "BulletDynamics/Dynamics/btDynamicsWorld.h"
+#include "BulletDynamics/Dynamics/btRigidBody.h"
+#include "LinearMath/btVector3.h"
 #include "camera.hpp"
 #include "common.hpp"
 #include "fmt/base.h"
@@ -37,6 +47,7 @@
 #include <future>
 #include <glm/fwd.hpp>
 #include <iterator>
+#include <memory>
 #include <mutex>
 #include <set>
 #include <stdexcept>
@@ -2611,6 +2622,8 @@ Engine::~Engine() {
     }
 
     GameNetworkingSockets_Kill();
+
+    DeinitPhysics();
 }
 
 void Engine::InitRenderer(Settings &settings, Camera *primaryCamera) {
@@ -2634,6 +2647,48 @@ void Engine::InitNetworking() {
     m_NetworkingSockets = SteamNetworkingSockets();
 }
 
+void Engine::InitPhysics() {
+    m_CollisionConfig = std::make_unique<btDefaultCollisionConfiguration>();
+    m_Dispatcher = std::make_unique<btCollisionDispatcher>(m_CollisionConfig.get());
+    m_Broadphase = std::make_unique<btDbvtBroadphase>();
+    m_Solver = std::make_unique<btSequentialImpulseConstraintSolver>();
+
+    m_DynamicsWorld = std::make_unique<btDiscreteDynamicsWorld>(m_Dispatcher.get(), m_Broadphase.get(), m_Solver.get(), m_CollisionConfig.get());
+
+    m_DynamicsWorld->setGravity(btVector3(0, -10, 0));
+}
+
+void Engine::DeinitPhysics() {
+    if (m_DynamicsWorld) {
+        while (m_DynamicsWorld->getNumConstraints() > 0) {
+            m_DynamicsWorld->removeConstraint(m_DynamicsWorld->getConstraint(0));
+        }
+
+        btCollisionObjectArray &array = m_DynamicsWorld->getCollisionObjectArray();
+
+        while (array.size() > 0) {
+            btCollisionObject *obj = array[0];
+            btRigidBody *rigidBody = btRigidBody::upcast(obj);
+
+            if (rigidBody && rigidBody->getMotionState()) {
+                delete rigidBody->getMotionState();
+            }
+
+            m_DynamicsWorld->removeCollisionObject(obj);
+            delete obj;
+        }
+    }
+
+    /* I love smart pointers :D */
+    m_CollisionShapes.clear();
+
+    m_DynamicsWorld.reset();
+    m_Solver.reset();
+    m_Broadphase.reset();
+    m_Dispatcher.reset();
+    m_CollisionConfig.reset();
+}
+
 void Engine::RegisterUIButtonListener(const std::function<void(std::string)> listener) {
     m_UIButtonListeners.push_back(listener);
 }
@@ -3671,6 +3726,14 @@ void Engine::DeserializeNetworkingCamera(std::vector<std::byte> &serializedCamer
     Deserialize(serializedCameraPacket, dest.isMainCamera);
 }
 
+void Engine::PhysicsStep(float deltaTime) {
+    if (!m_DynamicsWorld) {
+        return;
+    }
+
+    m_DynamicsWorld->stepSimulation(deltaTime);
+}
+
 std::optional<Networking_Object> Engine::AddObjectToStatePacket(Object *object, Networking_StatePacket &statePacket, bool includeChildren, bool isRecursive) {
     if (object->GetParent() != nullptr && !isRecursive) {
         return {};