Raycast vehicle not collided with ground

[anshul.bhardwaj]

I tried to implement the vehicle demo using my own rendering engine.
i draw a plane at origin and drop my vehicle from y = 10 units( taking Y axis as up).
other parameters are same as given in vehicle demo.
my tyre are colliding to the plane but my vehicle body in not colliding with the plane.
also body position in WS is coming below the tyre position.
I print the body position and tyre position then it comes --
body y axis ----> -0.234
tyre y axis -----> 0.5
tyre are colliding with plane and never go down but don't know about the vehicle body.
Any suggestion will be of great help.

[Skuzz]

Has the vehicles rigidbody been added to the simulation world?

Many of the demos, including the main vehicle demo, use a function in DemoApplication.cpp to add rigid bodies, and it's within this function that the rigidbody is added to the simulation:

btRigidBody* DemoApplication::localCreateRigidBody(float mass, const btTransform& startTransform,btCollisionShape* shape)
...
m_dynamicsWorld->addRigidBody(body); <<<<


When I first tried to create a vehicle demo I created my own 'chassis' and didn't use this function, and my vehicles dropped though the ground!

So, are you using this function? If not, are you adding your vehicles rigidbody / 'chassis' to the simulation yourself?

[anshul.bhardwaj]

Has the vehicles rigidbody been added to the simulation world?

Many of the demos, including the main vehicle demo, use a function in DemoApplication.cpp to add rigid bodies, and it's within this function that the rigidbody is added to the simulation:

btRigidBody* DemoApplication::localCreateRigidBody(float mass, const btTransform& startTransform,btCollisionShape* shape)
...
m_dynamicsWorld->addRigidBody(body); <<<<


When I first tried to create a vehicle demo I created my own 'chassis' and didn't use this function, and my vehicles dropped though the ground!

So, are you using this function? If not, are you adding your vehicles rigidbody / 'chassis' to the simulation yourself?

yes i am adding rigid body in simulation world, actually i am doing the same thing as given in the vehicle demo.
The code is shown as below

Code: Select all

        btCollisionShape* chassisShape = new btBoxShape(btVector3(1.f,0.5f,2.f));//1,0.5,2//2,1,4.5
	m_collisionShapes.push_back(chassisShape);
    
	btCompoundShape* compound = new btCompoundShape();
	m_collisionShapes.push_back(compound);
	btTransform localTrans;
	localTrans.setIdentity();
	
	localTrans.setOrigin(btVector3(0,1,0));
    
        compound->addChildShape(localTrans,chassisShape);
    

	tr.setOrigin(btVector3(0,3.f,0));
	m_carChassis = localCreateRigidBody(800,tr,compound);//chassisShape);

 m_wheelShape = new btCylinderShapeX(btVector3(wheelWidth,wheelRadius,wheelRadius));
    
//    clientResetScene();
    // create vehicle
	{
		
		m_vehicleRayCaster = new btDefaultVehicleRaycaster(dynamicsWorld);
		m_vehicle = new btRaycastVehicle(m_tuning,m_carChassis,m_vehicleRayCaster);
        
        //never deactivate the vehicle
		m_carChassis->setActivationState(DISABLE_DEACTIVATION);
        
        dynamicsWorld->addVehicle(m_vehicle);
 //Now for the wheels : choose coordinate system
		m_vehicle->setCoordinateSystem(rightIndex,upIndex,forwardIndex);
		float connectionHeight = 1.2f;
        
        //Front wheels : only affected by steering
		bool isFrontWheel=true;
		btVector3 connectionPointCS0(CUBE_HALF_EXTENTS-(0.3*wheelWidth),connectionHeight,2*CUBE_HALF_EXTENTS-wheelRadius);
		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);
        
		connectionPointCS0 = btVector3(-CUBE_HALF_EXTENTS+(0.3*wheelWidth),connectionHeight,2*CUBE_HALF_EXTENTS-wheelRadius);
		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);
		
		//Back wheels : only affected by engines
		isFrontWheel = false;
		connectionPointCS0 = btVector3(-CUBE_HALF_EXTENTS+(0.3*wheelWidth),connectionHeight,-2*CUBE_HALF_EXTENTS+wheelRadius);
		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);
        
		connectionPointCS0 = btVector3(CUBE_HALF_EXTENTS-(0.3*wheelWidth),connectionHeight,-2*CUBE_HALF_EXTENTS+wheelRadius);
		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);

        ...
        ...

As my tyres are colliding that means the vehicle is added to the dynamic world, but why the chassis body is not colliding.

[Skuzz]

Are you calculating the inertia tensor for when you create the rigidbody? Also, disabling deactivation?

Code: Select all

...
btVector3 localInertia(0,0,0);
compoundShape->calculateLocalInertia( mass, localInertia );

btRigidBody::btRigidBodyConstructionInfo rbInfo( mass, motionState, compoundShape, localInertia);
btRigidBody* vehicleBody = new btRigidBody(rbInfo);

vehicleBody->setActivationState(DISABLE_DEACTIVATION); // never deactivate the vehicle

[anshul.bhardwaj]

Are you calculating the inertia tensor for when you create the rigidbody? Also, disabling deactivation?

Code: Select all

...
btVector3 localInertia(0,0,0);
compoundShape->calculateLocalInertia( mass, localInertia );

btRigidBody::btRigidBodyConstructionInfo rbInfo( mass, motionState, compoundShape, localInertia);
btRigidBody* vehicleBody = new btRigidBody(rbInfo);

vehicleBody->setActivationState(DISABLE_DEACTIVATION); // never deactivate the vehicle

yes i am doing this in localcreateRigidbody function as given

Code: Select all

btRigidBody* localCreateRigidBody(float mass, const btTransform& startTransform,btCollisionShape* shape)
{
	btAssert((!shape || shape->getShapeType() != INVALID_SHAPE_PROXYTYPE));
    
	//rigidbody is dynamic if and only if mass is non zero, otherwise static
	bool isDynamic = (mass != 0.f);
    
	btVector3 localInertia(0,0,0);
	if (isDynamic)
		shape->calculateLocalInertia(mass,localInertia);
    
	//using motionstate is recommended, it provides interpolation capabilities, and only synchronizes 'active' objects
    
	btDefaultMotionState* myMotionState = new btDefaultMotionState(startTransform);
    
	btRigidBody::btRigidBodyConstructionInfo cInfo(mass,myMotionState,shape,localInertia);
    
	btRigidBody* body = new btRigidBody(cInfo);
	body->setContactProcessingThreshold(m_defaultContactProcessingThreshold);
    
	dynamicsWorld->addRigidBody(body);
    
	return body;
}