text: /*
  Bullet Continuous Collision Detection and Physics Library
  Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/
  
  This software is provided 'as-is', without any express or implied warranty.
  In no event will the authors be held liable for any damages arising from the use of this software.
  Permission is granted to anyone to use this software for any purpose, 
  including commercial applications, and to alter it and redistribute it freely, 
  subject to the following restrictions:
  
  1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
  */
  
  /// September 2006: VehicleDemo is work in progress, this file is mostly just a placeholder
  /// This VehicleDemo file is very early in development, please check it later
  /// One todo is a basic engine model:
  /// A function that maps user input (throttle) into torque/force applied on the wheels
  /// with gears etc.
  #include "btBulletDynamicsCommon.h"
  #include "BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h"
  
  //
  // By default, Bullet Vehicle uses Y as up axis.
  // You can override the up axis, for example Z-axis up. Enable this define to see how to:
  //#define FORCE_ZAXIS_UP 1
  //
  
  #ifdef FORCE_ZAXIS_UP
  		int rightIndex = 0; 
  		int upIndex = 2; 
  		int forwardIndex = 1;
  		btVector3 wheelDirectionCS0(0,0,-1);
  		btVector3 wheelAxleCS(1,0,0);
  #else
  		int rightIndex = 0;
  		int upIndex = 1;
  		int forwardIndex = 2;
  		btVector3 wheelDirectionCS0(0,-1,0);
  		btVector3 wheelAxleCS(-1,0,0);
  #endif
  
  #include "GLDebugDrawer.h"
  #include <stdio.h> //printf debugging
  
  #include "GL_ShapeDrawer.h"
  
  #include "GlutStuff.h"
  #include "VehicleDemo.h"
  
  const int maxProxies = 32766;
  const int maxOverlap = 65535;
  
  ///btRaycastVehicle is the interface for the constraint that implements the raycast vehicle
  ///notice that for higher-quality slow-moving vehicles, another approach might be better
  ///implementing explicit hinged-wheel constraints with cylinder collision, rather then raycasts
  float	gEngineForce = 0.f;
  float	gBreakingForce = 0.f;
  
  float	maxEngineForce = 1000.f;//this should be engine/velocity dependent
  float	maxBreakingForce = 100.f;
  
  float	gVehicleSteering = 0.f;
  float	steeringIncrement = 0.04f;
  float	steeringClamp = 0.3f;
  float	wheelRadius = 0.5f;
  float	wheelWidth = 0.4f;
  float	wheelFriction = 1000;//BT_LARGE_FLOAT;
  float	suspensionStiffness = 20.f;
  float	suspensionDamping = 2.3f;
  float	suspensionCompression = 4.4f;
  float	rollInfluence = 0.1f;//1.0f;
  
  
  btScalar suspensionRestLength(0.6);
  
  #define CUBE_HALF_EXTENTS 1
  
  
  
  ////////////////////////////////////
  
  
  
  
  VehicleDemo::VehicleDemo()
  :
  m_carChassis(0),
  m_indexVertexArrays(0),
  m_vertices(0),
  m_cameraHeight(4.f),
  m_minCameraDistance(3.f),
  m_maxCameraDistance(10.f)
  {
  	m_vehicle = 0;
  	m_wheelShape = 0;
  	m_cameraPosition = btVector3(30,30,30);
  }
  
  VehicleDemo::~VehicleDemo()
  {
  		//cleanup in the reverse order of creation/initialization
  
  	//remove the rigidbodies from the dynamics world and delete them
  	int i;
  	for (i=m_dynamicsWorld->getNumCollisionObjects()-1; i>=0 ;i--)
  	{
  		btCollisionObject* obj = m_dynamicsWorld->getCollisionObjectArray()[i];
  		btRigidBody* body = btRigidBody::upcast(obj);
  		if (body && body->getMotionState())
  		{
  			delete body->getMotionState();
  		}
  		m_dynamicsWorld->removeCollisionObject( obj );
  		delete obj;
  	}
  
  	//delete collision shapes
  	for (int j=0;j<m_collisionShapes.size();j++)
  	{
  		btCollisionShape* shape = m_collisionShapes[j];
  		delete shape;
  	}
  
  	delete m_indexVertexArrays;
  	delete m_vertices;
  
  	//delete dynamics world
  	delete m_dynamicsWorld;
  
  	delete m_vehicleRayCaster;
  
  	delete m_vehicle;
  
  	delete m_wheelShape;
  
  	//delete solver
  	delete m_constraintSolver;
  
  	//delete broadphase
  	delete m_overlappingPairCache;
  
  	//delete dispatcher
  	delete m_dispatcher;
  
  	delete m_collisionConfiguration;
  
  }
  
  void VehicleDemo::initPhysics()
  {
  	
  #ifdef FORCE_ZAXIS_UP
  	m_cameraUp = btVector3(0,0,1);
  	m_forwardAxis = 1;
  #endif
  
  	btCollisionShape* groundShape = new btBoxShape(btVector3(50,3,50));
  	m_collisionShapes.push_back(groundShape);
  	m_collisionConfiguration = new btDefaultCollisionConfiguration();
  	m_dispatcher = new btCollisionDispatcher(m_collisionConfiguration);
  	btVector3 worldMin(-1000,-1000,-1000);
  	btVector3 worldMax(1000,1000,1000);
  	m_overlappingPairCache = new btAxisSweep3(worldMin,worldMax);
  	m_constraintSolver = new btSequentialImpulseConstraintSolver();
  	m_dynamicsWorld = new btDiscreteDynamicsWorld(m_dispatcher,m_overlappingPairCache,m_constraintSolver,m_collisionConfiguration);
  #ifdef FORCE_ZAXIS_UP
  	m_dynamicsWorld->setGravity(btVector3(0,0,-10));
  #endif 
  
  	//m_dynamicsWorld->setGravity(btVector3(0,0,0));
  btTransform tr;
  tr.setIdentity();
  
  //either use heightfield or triangle mesh
  #define  USE_TRIMESH_GROUND 1
  #ifdef USE_TRIMESH_GROUND
  	int i;
  
  const float TRIANGLE_SIZE=20.f;
  
  	//create a triangle-mesh ground
  	int vertStride = sizeof(btVector3);
  	int indexStride = 3*sizeof(int);
  
  	const int NUM_VERTS_X = 20;
  	const int NUM_VERTS_Y = 20;
  	const int totalVerts = NUM_VERTS_X*NUM_VERTS_Y;
  	
  	const int totalTriangles = 2*(NUM_VERTS_X-1)*(NUM_VERTS_Y-1);
  
  	m_vertices = new btVector3[totalVerts];
  	int*	gIndices = new int[totalTriangles*3];
  
  	
  
  	for ( i=0;i<NUM_VERTS_X;i++)
  	{
  		for (int j=0;j<NUM_VERTS_Y;j++)
  		{
  			float wl = .2f;
  			//height set to zero, but can also use curved landscape, just uncomment out the code
  			float height = 0.f;//20.f*sinf(float(i)*wl)*cosf(float(j)*wl);
  #ifdef FORCE_ZAXIS_UP
  			m_vertices[i+j*NUM_VERTS_X].setValue(
  				(i-NUM_VERTS_X*0.5f)*TRIANGLE_SIZE,
  				(j-NUM_VERTS_Y*0.5f)*TRIANGLE_SIZE,
  				height
  				);
  
  #else
  			m_vertices[i+j*NUM_VERTS_X].setValue(
  				(i-NUM_VERTS_X*0.5f)*TRIANGLE_SIZE,
  				height,
  				(j-NUM_VERTS_Y*0.5f)*TRIANGLE_SIZE);
  #endif
  
  		}
  	}
  
  	int index=0;
  	for ( i=0;i<NUM_VERTS_X-1;i++)
  	{
  		for (int j=0;j<NUM_VERTS_Y-1;j++)
  		{
  			gIndices[index++] = j*NUM_VERTS_X+i;
  			gIndices[index++] = j*NUM_VERTS_X+i+1;
  			gIndices[index++] = (j+1)*NUM_VERTS_X+i+1;
  
  			gIndices[index++] = j*NUM_VERTS_X+i;
  			gIndices[index++] = (j+1)*NUM_VERTS_X+i+1;
  			gIndices[index++] = (j+1)*NUM_VERTS_X+i;
  		}
  	}
  	
  	m_indexVertexArrays = new btTriangleIndexVertexArray(totalTriangles,
  		gIndices,
  		indexStride,
  		totalVerts,(btScalar*) &m_vertices[0].x(),vertStride);
  
  	bool useQuantizedAabbCompression = true;
  	groundShape = new btBvhTriangleMeshShape(m_indexVertexArrays,useQuantizedAabbCompression);
  	
  	tr.setOrigin(btVector3(0,-4.5f,0));
  
  #else
  	//testing btHeightfieldTerrainShape
  	int width=128;
  	int length=128;
  	unsigned char* heightfieldData = new unsigned char[width*length];
  	{
  		for (int i=0;i<width*length;i++)
  		{
  			heightfieldData[i]=0;
  		}
  	}
  
  	char*	filename="heightfield128x128.raw";
  	FILE* heightfieldFile = fopen(filename,"r");
  	if (!heightfieldFile)
  	{
  		filename="../../heightfield128x128.raw";
  		heightfieldFile = fopen(filename,"r");
  	}
  	if (heightfieldFile)
  	{
  		int numBytes =fread(heightfieldData,1,width*length,heightfieldFile);
  		//btAssert(numBytes);
  		if (!numBytes)
  		{
  			printf("couldn't read heightfield at %s\n",filename);
  		}
  		fclose (heightfieldFile);
  	}
  	
  
  	btScalar maxHeight = 20000.f;
  	
  	bool useFloatDatam=false;
  	bool flipQuadEdges=false;
  
  	btHeightfieldTerrainShape* heightFieldShape = new btHeightfieldTerrainShape(width,length,heightfieldData,maxHeight,upIndex,useFloatDatam,flipQuadEdges);;
  	groundShape = heightFieldShape;
  	
  	heightFieldShape->setUseDiamondSubdivision(true);
  
  	btVector3 localScaling(20,20,20);
  	localScaling[upIndex]=1.f;
  	groundShape->setLocalScaling(localScaling);
  
  	tr.setOrigin(btVector3(0,-64.5f,0));
  
  #endif //
  
  	m_collisionShapes.push_back(groundShape);
  
  	//create ground object
  	localCreateRigidBody(0,tr,groundShape);
  
  #ifdef FORCE_ZAXIS_UP
  //   indexRightAxis = 0; 
  //   indexUpAxis = 2; 
  //   indexForwardAxis = 1; 
  	btCollisionShape* chassisShape = new btBoxShape(btVector3(1.f,2.f, 0.5f));
  	btCompoundShape* compound = new btCompoundShape();
  	btTransform localTrans;
  	localTrans.setIdentity();
  	//localTrans effectively shifts the center of mass with respect to the chassis
  	localTrans.setOrigin(btVector3(0,0,1));
  #else
  	btCollisionShape* chassisShape = new btBoxShape(btVector3(1.f,0.5f,2.f));
  	m_collisionShapes.push_back(chassisShape);
  
  	btCompoundShape* compound = new btCompoundShape();
  	m_collisionShapes.push_back(compound);
  	btTransform localTrans;
  	localTrans.setIdentity();
  	//localTrans effectively shifts the center of mass with respect to the chassis
  	localTrans.setOrigin(btVector3(0,1,0));
  #endif
  
  	compound->addChildShape(localTrans,chassisShape);
  
  	tr.setOrigin(btVector3(0,0.f,0));
  
  	m_carChassis = localCreateRigidBody(800,tr,compound);//chassisShape);
  	//m_carChassis->setDamping(0.2,0.2);
  	
  	m_wheelShape = new btCylinderShapeX(btVector3(wheelWidth,wheelRadius,wheelRadius));
  	
  	clientResetScene();
  
  	/// create vehicle
  	{
  		
  		m_vehicleRayCaster = new btDefaultVehicleRaycaster(m_dynamicsWorld);
  		m_vehicle = new btRaycastVehicle(m_tuning,m_carChassis,m_vehicleRayCaster);
  		
  		///never deactivate the vehicle
  		m_carChassis->setActivationState(DISABLE_DEACTIVATION);
  
  		m_dynamicsWorld->addVehicle(m_vehicle);
  
  		float connectionHeight = 1.2f;
  
  	
  		bool isFrontWheel=true;
  
  		//choose coordinate system
  		m_vehicle->setCoordinateSystem(rightIndex,upIndex,forwardIndex);
  
  #ifdef FORCE_ZAXIS_UP
  		btVector3 connectionPointCS0(CUBE_HALF_EXTENTS-(0.3*wheelWidth),2*CUBE_HALF_EXTENTS-wheelRadius, connectionHeight);
  #else
  		btVector3 connectionPointCS0(CUBE_HALF_EXTENTS-(0.3*wheelWidth),connectionHeight,2*CUBE_HALF_EXTENTS-wheelRadius);
  #endif
  
  		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);
  #ifdef FORCE_ZAXIS_UP
  		connectionPointCS0 = btVector3(-CUBE_HALF_EXTENTS+(0.3*wheelWidth),2*CUBE_HALF_EXTENTS-wheelRadius, connectionHeight);
  #else
  		connectionPointCS0 = btVector3(-CUBE_HALF_EXTENTS+(0.3*wheelWidth),connectionHeight,2*CUBE_HALF_EXTENTS-wheelRadius);
  #endif
  
  		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);
  #ifdef FORCE_ZAXIS_UP
  		connectionPointCS0 = btVector3(-CUBE_HALF_EXTENTS+(0.3*wheelWidth),-2*CUBE_HALF_EXTENTS+wheelRadius, connectionHeight);
  #else
  		connectionPointCS0 = btVector3(-CUBE_HALF_EXTENTS+(0.3*wheelWidth),connectionHeight,-2*CUBE_HALF_EXTENTS+wheelRadius);
  #endif //FORCE_ZAXIS_UP
  		isFrontWheel = false;
  		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);
  #ifdef FORCE_ZAXIS_UP
  		connectionPointCS0 = btVector3(CUBE_HALF_EXTENTS-(0.3*wheelWidth),-2*CUBE_HALF_EXTENTS+wheelRadius, connectionHeight);
  #else
  		connectionPointCS0 = btVector3(CUBE_HALF_EXTENTS-(0.3*wheelWidth),connectionHeight,-2*CUBE_HALF_EXTENTS+wheelRadius);
  #endif
  		m_vehicle->addWheel(connectionPointCS0,wheelDirectionCS0,wheelAxleCS,suspensionRestLength,wheelRadius,m_tuning,isFrontWheel);
  		
  		for (int i=0;i<m_vehicle->getNumWheels();i++)
  		{
  			btWheelInfo& wheel = m_vehicle->getWheelInfo(i);
  			wheel.m_suspensionStiffness = suspensionStiffness;
  			wheel.m_wheelsDampingRelaxation = suspensionDamping;
  			wheel.m_wheelsDampingCompression = suspensionCompression;
  			wheel.m_frictionSlip = wheelFriction;
  			wheel.m_rollInfluence = rollInfluence;
  		}
  	}
  
  	
  	setCameraDistance(26.f);
  
  }
  
  
  //to be implemented by the demo
  void VehicleDemo::renderme()
  {
  	
  	updateCamera();
  
  	btScalar m[16];
  	int i;
  
  
  	btVector3 wheelColor(1,0,0);
  
  	btVector3	worldBoundsMin,worldBoundsMax;
  	getDynamicsWorld()->getBroadphase()->getBroadphaseAabb(worldBoundsMin,worldBoundsMax);
  
  
  
  	for (i=0;i<m_vehicle->getNumWheels();i++)
  	{
  		//synchronize the wheels with the (interpolated) chassis worldtransform
  		m_vehicle->updateWheelTransform(i,true);
  		//draw wheels (cylinders)
  		m_vehicle->getWheelInfo(i).m_worldTransform.getOpenGLMatrix(m);
  		m_shapeDrawer->drawOpenGL(m,m_wheelShape,wheelColor,getDebugMode(),worldBoundsMin,worldBoundsMax);
  	}
  
  
  	DemoApplication::renderme();
  
  }
  
  void VehicleDemo::clientMoveAndDisplay()
  {
  
  	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
  
  	
  	{			
  		int wheelIndex = 2;
  		m_vehicle->applyEngineForce(gEngineForce,wheelIndex);
  		m_vehicle->setBrake(gBreakingForce,wheelIndex);
  		wheelIndex = 3;
  		m_vehicle->applyEngineForce(gEngineForce,wheelIndex);
  		m_vehicle->setBrake(gBreakingForce,wheelIndex);
  
  
  		wheelIndex = 0;
  		m_vehicle->setSteeringValue(gVehicleSteering,wheelIndex);
  		wheelIndex = 1;
  		m_vehicle->setSteeringValue(gVehicleSteering,wheelIndex);
  
  	}
  
  
  	float dt = getDeltaTimeMicroseconds() * 0.000001f;
  	
  	if (m_dynamicsWorld)
  	{
  		//during idle mode, just run 1 simulation step maximum
  		int maxSimSubSteps = m_idle ? 1 : 2;
  		if (m_idle)
  			dt = 1.0/420.f;
  
  		int numSimSteps = m_dynamicsWorld->stepSimulation(dt,maxSimSubSteps);
  		
  
  //#define VERBOSE_FEEDBACK
  #ifdef VERBOSE_FEEDBACK
  		if (!numSimSteps)
  			printf("Interpolated transforms\n");
  		else
  		{
  			if (numSimSteps > maxSimSubSteps)
  			{
  				//detect dropping frames
  				printf("Dropped (%i) simulation steps out of %i\n",numSimSteps - maxSimSubSteps,numSimSteps);
  			} else
  			{
  				printf("Simulated (%i) steps\n",numSimSteps);
  			}
  		}
  #endif //VERBOSE_FEEDBACK
  
  	}
  
  	
  	
  
  
  
  
  #ifdef USE_QUICKPROF 
          btProfiler::beginBlock("render"); 
  #endif //USE_QUICKPROF 
  
  
  	renderme(); 
  
  	//optional but useful: debug drawing
  	if (m_dynamicsWorld)
  		m_dynamicsWorld->debugDrawWorld();
  
  #ifdef USE_QUICKPROF 
          btProfiler::endBlock("render"); 
  #endif 
  	
  
  	glFlush();
  	glutSwapBuffers();
  
  }
  
  
  
  void VehicleDemo::displayCallback(void) 
  {
  	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
  
  	renderme();
  
  //optional but useful: debug drawing
  	if (m_dynamicsWorld)
  		m_dynamicsWorld->debugDrawWorld();
  
  	glFlush();
  	glutSwapBuffers();
  }
  
  
  
  void VehicleDemo::clientResetScene()
  {
  	gVehicleSteering = 0.f;
  	m_carChassis->setCenterOfMassTransform(btTransform::getIdentity());
  	m_carChassis->setLinearVelocity(btVector3(0,0,0));
  	m_carChassis->setAngularVelocity(btVector3(0,0,0));
  	m_dynamicsWorld->getBroadphase()->getOverlappingPairCache()->cleanProxyFromPairs(m_carChassis->getBroadphaseHandle(),getDynamicsWorld()->getDispatcher());
  	if (m_vehicle)
  	{
  		m_vehicle->resetSuspension();
  		for (int i=0;i<m_vehicle->getNumWheels();i++)
  		{
  			//synchronize the wheels with the (interpolated) chassis worldtransform
  			m_vehicle->updateWheelTransform(i,true);
  		}
  	}
  
  }
  
  
  
  void VehicleDemo::specialKeyboardUp(int key, int x, int y)
  {
     switch (key) 
      {
      case GLUT_KEY_UP :
  		{
  			gEngineForce = 0.f;
  		break;
  		}
  	case GLUT_KEY_DOWN :
  		{			
  			gBreakingForce = 0.f; 
  		break;
  		}
  	default:
  		DemoApplication::specialKeyboardUp(key,x,y);
          break;
      }
  
  }
  
  
  void VehicleDemo::specialKeyboard(int key, int x, int y)
  {
  
  //	printf("key = %i x=%i y=%i\n",key,x,y);
  
      switch (key) 
      {
      case GLUT_KEY_LEFT : 
  		{
  			gVehicleSteering += steeringIncrement;
  			if (	gVehicleSteering > steeringClamp)
  					gVehicleSteering = steeringClamp;
  
  		break;
  		}
      case GLUT_KEY_RIGHT : 
  		{
  			gVehicleSteering -= steeringIncrement;
  			if (	gVehicleSteering < -steeringClamp)
  					gVehicleSteering = -steeringClamp;
  
  		break;
  		}
      case GLUT_KEY_UP :
  		{
  			gEngineForce = maxEngineForce;
  			gBreakingForce = 0.f;
  		break;
  		}
  	case GLUT_KEY_DOWN :
  		{			
  			gBreakingForce = maxBreakingForce; 
  			gEngineForce = 0.f;
  		break;
  		}
  	default:
  		DemoApplication::specialKeyboard(key,x,y);
          break;
      }
  
  //	glutPostRedisplay();
  
  
  }
  
  
  
  void	VehicleDemo::updateCamera()
  {
  	
  //#define DISABLE_CAMERA 1
  #ifdef DISABLE_CAMERA
  	DemoApplication::updateCamera();
  	return;
  #endif //DISABLE_CAMERA
  
  	glMatrixMode(GL_PROJECTION);
  	glLoadIdentity();
  
  	btTransform chassisWorldTrans;
  
  	//look at the vehicle
  	m_carChassis->getMotionState()->getWorldTransform(chassisWorldTrans);
  	m_cameraTargetPosition = chassisWorldTrans.getOrigin();
  
  	//interpolate the camera height
  #ifdef FORCE_ZAXIS_UP
  	m_cameraPosition[2] = (15.0*m_cameraPosition[2] + m_cameraTargetPosition[2] + m_cameraHeight)/16.0;
  #else
  	m_cameraPosition[1] = (15.0*m_cameraPosition[1] + m_cameraTargetPosition[1] + m_cameraHeight)/16.0;
  #endif 
  
  	btVector3 camToObject = m_cameraTargetPosition - m_cameraPosition;
  
  	//keep distance between min and max distance
  	float cameraDistance = camToObject.length();
  	float correctionFactor = 0.f;
  	if (cameraDistance < m_minCameraDistance)
  	{
  		correctionFactor = 0.15*(m_minCameraDistance-cameraDistance)/cameraDistance;
  	}
  	if (cameraDistance > m_maxCameraDistance)
  	{
  		correctionFactor = 0.15*(m_maxCameraDistance-cameraDistance)/cameraDistance;
  	}
  	m_cameraPosition -= correctionFactor*camToObject;
  	
  	  btScalar aspect = m_glutScreenWidth / (btScalar)m_glutScreenHeight;
          glFrustum (-aspect, aspect, -1.0, 1.0, 1.0, 10000.0);
  
           glMatrixMode(GL_MODELVIEW);
           glLoadIdentity();
  
      gluLookAt(m_cameraPosition[0],m_cameraPosition[1],m_cameraPosition[2],
                        m_cameraTargetPosition[0],m_cameraTargetPosition[1], m_cameraTargetPosition[2],
                            m_cameraUp.getX(),m_cameraUp.getY(),m_cameraUp.getZ());
  
  
  
  }
  
  