我创建了一辆子弹车，其顶部装有一个炮塔，如下所示:
gEngineForce = 0.f;
gBreakingFrontForce = 0.f;
gBreakingBackForce = 0.f;
maxEngineForce = 20000.f;
minEngineForce = -2000.f;
maxBreakingFrontForce = 4000.f;
maxBreakingBackForce = 600.f;
gVehicleSteering = 0.f;
steeringIncrement = 0.002f;
steeringClamp = 0.6f;
wheelRadius = 0.5f;
wheelWidth = 0.4f;
wheelFriction = 50;
suspensionStiffness = 10.f;
suspensionDamping = 1.3f;
suspensionCompression = 4.4f;
rollInfluence = 0.1f;//1.0f
btScalar suspensionRestLength(0.6);
btVector3 wheelDirectionCS0(0, -1, 0);
btVector3 wheelAxleCS(-1, 0, 0);
btTransform tr;
tr.setIdentity();
chassisShape = new btBoxShape(btVector3(1.f, 0.5f, 2.f));
bulletCollisionShapes.push_back(chassisShape);
compound = new btCompoundShape();
bulletCollisionShapes.push_back(compound);
btTransform chassisTrans;
chassisTrans.setIdentity();
//localTrans effectively shifts the center of mass with respect to the chassis
chassisTrans.setOrigin(btVector3(0, 1.3, 0));
compound->addChildShape(chassisTrans, chassisShape);
tr.setOrigin(btVector3(0, 0.f, 0));
//m_carChassis = CreateRigidBody(2000, tr, compound);
//m_carChassis->setDamping(0.2,0.2);
m_wheelShape = new btCylinderShapeX(btVector3(wheelWidth, wheelRadius, wheelRadius));
m_carChassis = CreateRigidBody(2000, tr, compound);
// create turret
turretShape = new btBoxShape(btVector3(0.4f, 0.2f, 0.8f));
bulletCollisionShapes.push_back(turretShape);
btTransform turretTrans;
turretTrans.setIdentity();
turretTrans.setOrigin(btVector3(0.0f, 0.7f, 0.0f));
turretBody = CreateRigidBody(1, turretTrans, turretShape);
// add some data to build constraint frames
btVector3 axisA(0.f, 1.f, 0.f);
btVector3 axisB(0.f, 0.f, 0.f);
btVector3 pivotA(0.f, 1.f, 0.f);
btVector3 pivotB(0.f, 0.f, 0.f);
hinge = new btHingeConstraint(*m_carChassis, *turretBody, pivotA, pivotB, axisA, axisB);
//hinge->setLimit(-SIMD_HALF_PI * 0.5f, SIMD_HALF_PI * 0.5f);
hinge->enableAngularMotor(true, 0, 1);
// add constraint to world
bt_dynamicsWorld->addConstraint(hinge, true);
{
btTransform something;
something.setIdentity();
something.setOrigin(btVector3(0, 10, 0));
m_carChassis->setWorldTransform(something);
m_vehicleRayCaster = new btDefaultVehicleRaycaster(bt_dynamicsWorld);
m_vehicle = new btRaycastVehicle(m_tuning, m_carChassis, m_vehicleRayCaster);
m_carChassis->setActivationState(DISABLE_DEACTIVATION);
bt_dynamicsWorld->addVehicle(m_vehicle);
float connectionHeight = 1.2f;
//choose coordinate system
m_vehicle->setCoordinateSystem(rightIndex, upIndex, forwardIndex);
bool isFrontWheel = true;
btVector3 connectionPointCS0(1 - (-0.8*wheelWidth), connectionHeight, 3 * 1 - wheelRadius);
m_vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, m_tuning, isFrontWheel);
connectionPointCS0 = btVector3(-1 + (-0.8*wheelWidth), connectionHeight, 3 * 1 - wheelRadius);
m_vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, m_tuning, isFrontWheel);
isFrontWheel = false;
connectionPointCS0 = btVector3(-1 + (-0.8*wheelWidth), connectionHeight, -3 * 1 + wheelRadius);
m_vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, m_tuning, isFrontWheel);
connectionPointCS0 = btVector3(1 - (-0.8*wheelWidth), connectionHeight, -3 * 1 + wheelRadius);
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;
}
}
int wheelIndex = 2;
m_vehicle->applyEngineForce(gEngineForce, wheelIndex);
m_vehicle->setBrake(gBreakingBackForce, wheelIndex);
wheelIndex = 3;
m_vehicle->applyEngineForce(gEngineForce, wheelIndex);
m_vehicle->setBrake(gBreakingBackForce, wheelIndex);
wheelIndex = 0;
m_vehicle->setSteeringValue(gVehicleSteering, wheelIndex);
m_vehicle->setBrake(gBreakingFrontForce, wheelIndex);
wheelIndex = 1;
m_vehicle->setSteeringValue(gVehicleSteering, wheelIndex);
m_vehicle->setBrake(gBreakingFrontForce, wheelIndex);
这就是我渲染车辆的方式:
// render wheels
btScalar mwheel[16];
for (int i = 0; i<m_vehicle->getNumWheels(); i++){
//synchronize the wheels with the (interpolated) chassis worldtransform
m_vehicle->updateWheelTransform(i, true);
//draw wheels
m_vehicle->getWheelInfo(i).m_worldTransform.getOpenGLMatrix(mwheel);
RenderWheel(m_wheelShape, mwheel);
}
// render car chassis
btScalar mchassis[16];
m_vehicle->getChassisWorldTransform().getOpenGLMatrix(mchassis);
RenderBox(chassisShape, mchassis);
// render turret
btScalar mturret[16];
// get chassis and turret transforms
btTransform chassisTransform = m_vehicle->getChassisWorldTransform();
//btTransform turretTransform = compound->getChildTransform(1);
btTransform turretTransform = turretBody->getWorldTransform();
// multiply transforms to get updated turret transform
//turretTransform *= chassisTransform;
turretTransform.getOpenGLMatrix(mturret);
RenderBox(turretShape, mturret);
使用箭头键，我可以像这样施加断裂力或加速力:
bullet.gEngineForce = bullet.maxEngineForce;
bullet.gBreakingFrontForce = 0.f;
bullet.gBreakingBackForce = 0.f;
等等
摄像机安装在汽车顶部的转塔上，因此也安装在汽车本身上。
问题是，当汽车开始行驶并随着速度增加时，车轮似乎落后了，底盘则向前行驶。我想使车轮和底盘更紧，但是在汽车悬架设置上玩耍并没有帮助。
这是演示此行为的视频:click
我还注意到了另一个奇怪的行为，与汽车在移动，折断和转弯时的俯仰方式有关。
增加重力会加剧这种行为。当我加速时，底盘向前倾斜，而当我制动时，底盘向后倾斜。这显然是错误的，因为它应该是相反的。向左转时，汽车向左倾斜而不是向右倾斜，反之亦然。
这是另一个演示这种行为的视频:click
最佳答案
我有这种问题。事实证明，轮子是通过变换渲染的，而不是从与底盘相同的框架渲染的。即从框架n-1开始，而机箱使用框架n。
因为车轮网格是底盘节点的子节点，所以并不是很明显，因为这是我在渲染引擎中实现的，而在子弹物理学中，车轮坐标是全局的，底盘也是如此。
但这还不是全部，当将车轮坐标从全局空间转换为本地车辆空间时，仍然存在精度损失，这仍然会引起问题。它通过将车轮网格作为全局节点来修复。