Linear Velocity

Hi,

I'm using OgreBullet, and in order to move an object I use this method setLinearVelocity().

I use this one (and not applyForce, or applyImpulse) because I want that this object have a constant speed !

My problem is when I want to stop this object with setLinearVelocity(Ogre::Vector3::ZERO); I can't re-moving the object after...

My object is a car :

Ogre::SceneNode *car = mSceneMgr->getSceneNode("car");
Ogre::Vector3 car_scale = car->getScale();
Ogre::AxisAlignedBox boundingB_car = car->getAttachedObject("car_part16")->getBoundingBox();
Ogre::Vector3 size = boundingB_car.getSize();
size *= car_scale;
size /= 2.0f;
OgreBulletCollisions::CollisionShape *car_shape = new OgreBulletCollisions::BoxCollisionShape(size);
car_body = new OgreBulletDynamics::RigidBody("car", mWorld);
initialPositionCar1 = Ogre::Vector3(-2500.f, 40.0, mSceneMgr->getSceneNode("nodeRoad1")->getPosition().z+(75.0f));
initialOrientationCar1 = Ogre::Quaternion(Ogre::Quaternion(sqrt(0.5),0.0,sqrt(0.5),0.0));
car_body->setShape(car,car_shape, 0.6, 0.6, 1500.0, initialPositionCar1, initialOrientationCar1);
car_body->enableActiveState();
car_body->setLinearVelocity(speed_car, 0.0, 0.0);
mShapes.push_back(car_shape);
mBodies.push_back(car_body);

And after I do this in the frameRenderingQueued(const Ogre::FrameEvent& evt) of my FrameListener :



//The variable called stop is an attribute of my listener

//Traffic Light
if(mSceneMgr->getEntity("tl1_red")->isVisible() && fabs(mSceneMgr->getSceneNode("tl1")->getPosition().x - node->getPosition().x) < 200.0f){
if(stop==false) car_body->setLinearVelocity(Vector3::ZERO);
if(mSoundMgr->getSound("carEngine")->isPlaying()) mSoundMgr->getSound("carEngine")->stop();
stop = true;
}

if(mSceneMgr->getEntity("tl1_green")->isVisible()){
if(stop==true) car_body->setLinearVelocity(speed_car, 0.0, 0.0);
if(!mSoundMgr->getSound("carEngine")->isPlaying()) mSoundMgr->getSound("carEngine")->play();
stop = false;
}


Result : my car moves, when the traffic light is red the car stops, but doesn't move again when the traffic light is green ! Do you know why or have you an alternative to do this ?

Thank you !

When the traffic light is green activate the body prior to applying your linear velocity.

car_body->enableActiveState();

It's awesome ! It works ! Can I ask, why is it necessary to do this ?

http://www.bulletphysics.com/Bullet/Bul ... dBody.html - Detailed Description

If you want to disable this, obviously you would do this only on objects such as your vehicle, you could try:

body->disableDeactivation();
// or
//body->getBulletRigidBody()->setActivationState(DISABLE_DEACTIVATION);