Bullet3之封裝PhysicsWorld3D
根據bullet3 HelloWorld程式去封裝一個PhysicsWorld3D,
首先應該去建立一個實體世界,而對于一個實體世界,預設都有重力,提供一個建立
世界的靜态方法(重力預設為(0, -10, 0))
static PhysicsWorld3D* create(const btVector3& gravity = btVector3(0, -10, 0));
負責建立世界,同時對世界初始化
這裡建立一個btDiscreteDynamicsWorld
直接複制bullet3 HelloWorld對世界的初始化,并修改
_collisionConfiguration,_dispatcher, _solver, _overlappingPairCache, _drawer均為成員變量,
具體使用參照Bullet的文檔
PhysicsWorld3D* PhysicsWorld3D::create(const btVector3& gravity)
{
auto world = new PhysicsWorld3D;
if (world && world->initWorld(gravity))
{
return world;
}
delete world;
return nullptr;
}
bool PhysicsWorld3D::initWorld(const btVector3& gravity)
{
_collisionConfiguration = new btDefaultCollisionConfiguration();
_dispatcher = new btCollisionDispatcher(_collisionConfiguration);
_overlappingPairCache = new btDbvtBroadphase();
_solver = new btSequentialImpulseConstraintSolver;
_world = new btDiscreteDynamicsWorld(_dispatcher, _overlappingPairCache, _solver, _collisionConfiguration);
if (_world == nullptr)
{
return false;
}
_world->setGravity(gravity);
return true;
}
銷毀一個實體世界
void PhysicsWorld3D::destroy()
{
this->clear();
delete _collisionConfiguration;
delete _dispatcher;
delete _solver;
delete _overlappingPairCache;
delete _world;
delete this;
}
void PhysicsWorld3D::clear()
{
int i;
//remove the rigidbodies from the dynamics world and delete them
for (i = _world->getNumCollisionObjects() - 1; i >= 0; i--)
{
btCollisionObject* obj = _world->getCollisionObjectArray()[i];
btRigidBody* body = btRigidBody::upcast(obj);
if (body && body->getMotionState())
{
delete body->getMotionState();
delete body->getCollisionShape();
}
_world->removeCollisionObject(body);
delete obj;
}
}
建立一些簡單的body
由于每種body都有自己的材質資訊
btRigidBodyConstructionInfo是構造一個剛體資訊的結構體,
我們隻需關心幾個參數,
friction; // 摩擦系數
rollingFriction; // 滾動摩擦系數
restitution; // 恢複系數(彈性系數)
mass; // 品質
自己去實作一個簡單的材質結構體
struct PhysicsMaterial3D
{
btScalar friction;
btScalar rollingFriction;
btScalar restitution;
btScalar mass;
PhysicsMaterial3D() :
friction(0.0f),
rollingFriction(0.f),
restitution(0.f),
mass(0.f)
{}
PhysicsMaterial3D(btScalar aMass, btScalar aFriction, btScalar aRestitution, btScalar aRollingFriction) :
friction(aFriction),
rollingFriction(aRollingFriction),
restitution(aRestitution),
mass(aMass)
{}
};
并提供一個預設的材質資訊
const PhysicsMaterial3D PHYSICS_MATERIAL3D_DEFAULT(1.f, 0.5f, 0.5f, 0.0f);
實作構造3個基本物體,如下聲明
btRigidBody* addPlane(const btVector3& normal, const btVector3& position, const PhysicsMaterial3D& material = PHYSICS_MATERIAL3D_DEFAULT);
btRigidBody* addSphere(btScalar radius, const btVector3& position, const PhysicsMaterial3D& material = PHYSICS_MATERIAL3D_DEFAULT);
btRigidBody* addBox(const btVector3& halfSize, const btVector3& position, const PhysicsMaterial3D& material = PHYSICS_MATERIAL3D_DEFAULT);
對于一個無限的平面,需要一個法向量決定Plane的朝向,同時position決定plane的位置,當然還有材質,但是mass必須為0
對于一個球體(Sphere)半徑,位置,材質
對于一個盒子(Box)尺寸, 位置,材質
btRigidBody* PhysicsWorld3D::addPlane(const btVector3& normal, const btVector3& position, const PhysicsMaterial3D& material)
{
CCAssert(material.mass == 0.f, "plane's mass must be 0."); // 特殊處理,保證mass為0
btCollisionShape* groundShape = new btStaticPlaneShape(normal, 0.f);
auto body = getBody(groundShape, position, material);
_world->addRigidBody(body);
return body;
}
btRigidBody* PhysicsWorld3D::addSphere(btScalar radius, const btVector3& position, const PhysicsMaterial3D& material)
{
btCollisionShape* colShape = new btSphereShape(radius);
auto body = getBody(colShape, position, material);
_world->addRigidBody(body);
return body;
}
btRigidBody* PhysicsWorld3D::addBox(const btVector3& size, const btVector3& position, const PhysicsMaterial3D& material)
{
btCollisionShape* colShape = new btBoxShape(size * 0.5f); // halfSize
auto body = getBody(colShape, position, material);
_world->addRigidBody(body);
return body;
}
構造一個剛體包含一些共同的步驟collisionShape, position, material
由于Plane,Sphere,Box collisionShape類型不同,是以單獨實作,
其他的公共步驟可以抽離出來
btRigidBody* getBody(btCollisionShape* colShape, const btVector3& position, const PhysicsMaterial3D& material);
仿照HelloWorld構造body的方法
btRigidBody* PhysicsWorld3D::getBody(btCollisionShape* colShape, const btVector3& position, const PhysicsMaterial3D& material)
{
/// Create Dynamic Objects
btTransform startTransform;
startTransform.setIdentity();
//rigidbody is dynamic if and only if mass is non zero, otherwise static
bool isDynamic = (material.mass != 0.f);
btVector3 localInertia(0,0,0);
if (isDynamic)
colShape->calculateLocalInertia(material.mass, localInertia); // 計算物體慣性
startTransform.setOrigin(position); // 設定物體位置
//using motionstate is recommended, it provides interpolation capabilities, and only synchronizes 'active' objects
btDefaultMotionState* myMotionState = new btDefaultMotionState(startTransform);
btRigidBody::btRigidBodyConstructionInfo rbInfo(material.mass, myMotionState,colShape,localInertia);
// 使用自定義的材質
rbInfo.m_restitution = material.restitution;
rbInfo.m_friction = material.friction;
rbInfo.m_rollingFriction = material.rollingFriction;
// 建立body
btRigidBody* body = new btRigidBody(rbInfo);
return body;
}
不要忘了實體世界的更新
void PhysicsWorld3D::update(float dt)
{
_world->stepSimulation(dt);
}
完整源碼