University of Texas at Austin CS 378 – Game Technology Don Fussell CS 378: Computer Game Technology Using Bullet Physics Library Spring 2012Building an app with Ogre and Bullet ! Make sure they all link similarly ! On Windows, make sure they all use the same C runtime library ! This means you’ll probably need to build at least one of them from source ! OgreBullet may not be the simplest way to go ! Examples without OgreBullet University of Texas at Austin CS 378 – Game Technology Don Fussell 2Ogre-Bullet Interface University of Texas at Austin CS 378 – Game Technology Don Fussell 3 class OgreMotionState : public btMotionState {!protected:! Ogre::SceneNode* mVisibleobj;! btTransform mPos1;!public:! OgreMotionState(const btTransform& initialpos, Ogre::SceneNode* node) {! mVisibleobj = node;! mPos1 = initialpos;! }! virtual ~OgreMotionState() {}!! void setNode(Ogre::SceneNode* node) {! mVisibleobj = node;! }! void updateTransform(btTransform& newpos) {! mPos1 = newpos;! }! !Communicating with Bullet University of Texas at Austin CS 378 – Game Technology Don Fussell 4 virtual void getWorldTransform(btTransform& worldTrans) const {! worldTrans = mPos1;! }! virtual void setWorldTransform(const btTransform& worldTrans) {! if(NULL == mVisibleobj)! return; // silently return before we set a node! btQuaternion rot = worldTrans.getRotation();! mVisibleobj->setOrientation(rot.w(), rot.x(), rot.y(), rot.z());! btVector3 pos = worldTrans.getOrigin();! mVisibleobj->setPosition(pos.x(), pos.y(), pos.z());! }!};!!Simulation University of Texas at Austin CS 378 – Game Technology Don Fussell 5 class Simulator {!protected:!!btDefaultCollisionConfiguration* collisionConfiguration;!!btCollisionDispatcher* dispatcher;!!btBroadphaseInterface* overlappingPairCache;!!btSequentialImpulseConstraintSolver* solver;!!btDiscreteDynamicsWorld* dynamicsWorld;!!btConstraintSolver* mConstraintsolver;!// !btCollisionWorld* mWorld;!!Ogre::SceneManager* sceneMgr;! !std::deque<GameObject*> objList;!public:!!Simulator();!!~Simulator();!!!void addObject(GameObject* o);!!bool removeObject(GameObject* o);!!void stepSimulation(const Ogre::Real elapsedTime,!!!int maxSubSteps = 1, const Ogre::Real fixedTimestep = 1.0f/60.0f);!!};!Simulation University of Texas at Austin CS 378 – Game Technology Don Fussell 6 Simulator::Simulator() {! ///collision configuration contains default setup for memory, collision setup.! collisionConfiguration = new btDefaultCollisionConfiguration();! ///use the default collision dispatcher. For parallel processing you can use a diffent dispatcher! dispatcher = new btCollisionDispatcher(collisionConfiguration);! ///btDbvtBroadphase is a good general purpose broadphase. You can also try out btAxis3Sweep.! overlappingPairCache = new btDbvtBroadphase();! ///the default constraint solver. For parallel processing you can use a different solver (see Extras/BulletMultiThreaded)! solver = new btSequentialImpulseConstraintSolver();! dynamicsWorld = new btDiscreteDynamicsWorld(dispatcher,overlappingPairCache,solver,collisionConfiguration);! dynamicsWorld->setGravity(btVector3(0,-0.098, 0));! //keep track of the shapes, we release memory at exit.! //make sure to re-use collision shapes among rigid bodies whenever possible!! btAlignedObjectArray<btCollisionShape*> collisionShapes;!}!void Simulator::addObject (GameObject* o) {!!objList.push_back(o);!!// use default collision group/mask values (dynamic/kinematic/static)!!dynamicsWorld->addRigidBody(o->getBody()); !}!void Simulator::stepSimulation(const Ogre::Real elapsedTime, int maxSubSteps, const Ogre::Real fixedTimestep) {!!// do we need to update positions in simulator for dynamic objects?!!dynamicsWorld->stepSimulation(elapsedTime, maxSubSteps, fixedTimestep);!}!Game Objects University of Texas at Austin CS 378 – Game Technology Don Fussell 7 class GameObject {!protected:!!Ogre::String name;!!Ogre::SceneManager* sceneMgr;!!Simulator* simulator;!!Ogre::SceneNode* rootNode;!!Ogre::Entity* geom;!!btCollisionShape* shape;!!btScalar mass;!!btRigidBody* body;!!btTransform tr;!!btVector3 inertia;!!OgreMotionState* motionState;!Game Objects University of Texas at Austin CS 378 – Game Technology Don Fussell 8 GameObject::GameObject(Ogre::String nym, Ogre::SceneManager* mgr, Simulator* sim) {!!name = nym;!!sceneMgr = mgr;!!simulator = sim;!!rootNode = sceneMgr->getRootSceneNode()->createChildSceneNode(name);!!shape = NULL;!!tr.setIdentity();!!mass = 0.0f;!!inertia.setZero();!}!void GameObject::updateTransform() {!!Ogre::Vector3 pos = rootNode->getPosition();!!tr.setOrigin(btVector3(pos.x, pos.y, pos.z));!!Ogre::Quaternion qt = rootNode->getOrientation();!!tr.setRotation(btQuaternion(qt.x, qt.y, qt.z, qt.w));!!if (motionState) motionState->updateTransform(tr);!}!void GameObject::addToSimulator() {!!//using motionstate is recommended, it provides interpolation capabilities, and only synchronizes 'active' objects!!updateTransform();!!motionState = new OgreMotionState(tr, rootNode);!!//rigidbody is dynamic if and only if mass is non zero, otherwise static!!if (mass != 0.0f) shape->calculateLocalInertia(mass, inertia);!!btRigidBody::btRigidBodyConstructionInfo rbInfo(mass, motionState, shape, inertia);!!body = new
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