//===========================================================================
bool cEffectStickSlip::computeForce(const cVector3d& a_toolPos,
const cVector3d& a_toolVel,
const unsigned int& a_toolID,
cVector3d& a_reactionForce)
{
// check if history for this IDN exists
if (a_toolID < CHAI_EFFECT_MAX_IDN)
{
if (m_parent->m_interactionInside)
{
// check if a recent valid point has been stored previously
if (!m_history[a_toolID].m_valid)
{
m_history[a_toolID].m_currentStickPosition = a_toolPos;
m_history[a_toolID].m_valid = true;
}
// read parameters for stick and slip model
double stiffness = m_parent->m_material.getStickSlipStiffness();
double forceMax = m_parent->m_material.getStickSlipForceMax();
// compute current force between last stick position and current tool position
double distance = cDistance(a_toolPos, m_history[a_toolID].m_currentStickPosition);
double forceMag = distance * stiffness;
if (forceMag > 0)
{
// if force above threshold, slip...
if (forceMag > forceMax)
{
m_history[a_toolID].m_currentStickPosition = a_toolPos;
a_reactionForce.zero();
}
// ...otherwise stick
else
{
a_reactionForce = (forceMag / distance) * cSub(m_history[a_toolID].m_currentStickPosition, a_toolPos);
}
}
else
{
a_reactionForce.zero();
}
return (true);
}
else
{
// the tool is located outside the object, so zero reaction force
m_history[a_toolID].m_valid = false;
a_reactionForce.zero();
return (false);
}
}
else
{
a_reactionForce.zero();
return (false);
}
}
//===========================================================================
bool cEffectVibration::computeForce(const cVector3d& a_toolPos,
const cVector3d& a_toolVel,
const unsigned int& a_toolID,
cVector3d& a_reactionForce)
{
if (m_parent->m_interactionInside)
{
// read vibration parameters
double vibrationFrequency = m_parent->m_material.getVibrationFrequency();
double vibrationAmplitude = m_parent->m_material.getVibrationAmplitude();
// read time
double time = clock.getCurrentTimeSeconds();
// compute force magnitude
double forceMag = vibrationAmplitude * sin(2.0 * CHAI_PI *vibrationFrequency * time);
a_reactionForce = cMul(forceMag, cVector3d(1, 0, 0));
return (true);
}
else
{
// the tool is located outside the object, so zero reaction force
a_reactionForce.zero();
return (false);
}
}
//==============================================================================
bool cEffectMagnet::computeForce(const cVector3d& a_toolPos,
const cVector3d& a_toolVel,
const unsigned int& a_toolID,
cVector3d& a_reactionForce)
{
// compute distance from object to tool
double distance = cDistance(a_toolPos, m_parent->m_interactionPoint);
// get parameters of magnet
double magnetMaxForce = m_parent->m_material->getMagnetMaxForce();
double magnetMaxDistance = m_parent->m_material->getMagnetMaxDistance();
double stiffness = m_parent->m_material->getStiffness();
double forceMagnitude = 0;
if (m_enabledInside || (!m_parent->m_interactionInside))
{
if ((distance < magnetMaxDistance) && (stiffness > 0))
{
double d = magnetMaxForce / stiffness;
if (distance < d)
{
forceMagnitude = stiffness * distance;
}
else
{
double dx = (magnetMaxDistance - d);
if (dx > 0)
{
double k = magnetMaxForce / dx;
forceMagnitude = k * (magnetMaxDistance - distance);
}
}
// compute reaction force
int sign = -1;
if (m_parent->m_interactionInside)
{
sign = 1;
}
a_reactionForce = cMul(sign * forceMagnitude, m_parent->m_interactionNormal);
return (true);
}
else
{
return (false);
}
}
else
{
// the tool is located outside the magnet zone
a_reactionForce.zero();
return (false);
}
}
//===========================================================================
bool cEffectViscosity::computeForce(const cVector3d& a_toolPos,
const cVector3d& a_toolVel,
const unsigned int& a_toolID,
cVector3d& a_reactionForce)
{
if (m_parent->m_interactionInside)
{
// the tool is located inside the object.
double viscosity = m_parent->m_material.getViscosity();
a_reactionForce = cMul(-viscosity, a_toolVel);
return (true);
}
else
{
// the tool is located outside the object, so zero reaction force.
a_reactionForce.zero();
return (false);
}
}
//===========================================================================
bool cEffectSurface::computeForce(const cVector3d& a_toolPos,
const cVector3d& a_toolVel,
const unsigned int& a_toolID,
cVector3d& a_reactionForce)
{
if (m_parent->m_interactionInside)
{
// the tool is located inside the object,
// we compute a reaction force using Hooke's law
double stiffness = m_parent->m_material.getStiffness();
a_reactionForce = cMul(stiffness, cSub(m_parent->m_interactionProjectedPoint, a_toolPos));
return (true);
}
else
{
// the tool is located outside the object, so zero reaction force
a_reactionForce.zero();
return (false);
}
}
//===========================================================================
bool cEffectPotentialField::computeForce(const cVector3d& a_toolPos,
const cVector3d& a_toolVel,
const unsigned int& a_toolID,
cVector3d& a_reactionForce)
{
if (m_parent->m_interactionInside)
{
// the tool is located inside the object, so zero reaction force
a_reactionForce.zero();
return (false);
}
else
{
// the tool is located outside the object,
// we compute a reaction force using Hooke's law
double stiffness = m_parent->m_material->getStiffness();
double maxForce = m_parent->m_material->getMagnetMaxForce();
cVector3d force = cMul(stiffness, cSub(m_parent->m_interactionProjectedPoint, a_toolPos));
if (maxForce > 0.0)
{
double ratio = force.length() / maxForce;
if (ratio > 1.0)
{
force = (1.0 / ratio) * force;
}
}
else
{
force.zero();
}
a_reactionForce = force;
return (true);
}
}
void updateHaptics(void)
{
// reset clock
cPrecisionClock clock;
clock.reset();
// main haptic simulation loop
while(simulationRunning)
{
/////////////////////////////////////////////////////////////////////
// SIMULATION TIME
/////////////////////////////////////////////////////////////////////
// stop the simulation clock
clock.stop();
// read the time increment in seconds
double timeInterval = clock.getCurrentTimeSeconds();
// restart the simulation clock
clock.reset();
clock.start();
// update frequency counter
frequencyCounter.signal(1);
/////////////////////////////////////////////////////////////////////
// HAPTIC FORCE COMPUTATION
/////////////////////////////////////////////////////////////////////
// compute global reference frames for each object
world->computeGlobalPositions(true);
// update position and orientation of tool
tool->updatePose();
// compute interaction forces
tool->computeInteractionForces();
// send forces to device
tool->applyForces();
/////////////////////////////////////////////////////////////////////
// HAPTIC SIMULATION
/////////////////////////////////////////////////////////////////////
// get position of cursor in global coordinates
cVector3d toolPos = tool->getDeviceGlobalPos();
// get position of object in global coordinates
cVector3d objectPos = object->getGlobalPos();
// compute a vector from the center of mass of the object (point of rotation) to the tool
cVector3d v = cSub(toolPos, objectPos);
// compute angular acceleration based on the interaction forces
// between the tool and the object
cVector3d angAcc(0,0,0);
if (v.length() > 0.0)
{
// get the last force applied to the cursor in global coordinates
// we negate the result to obtain the opposite force that is applied on the
// object
cVector3d toolForce = cNegate(tool->m_lastComputedGlobalForce);
// compute the effective force that contributes to rotating the object.
cVector3d force = toolForce - cProject(toolForce, v);
// compute the resulting torque
cVector3d torque = cMul(v.length(), cCross( cNormalize(v), force));
// update rotational acceleration
const double INERTIA = 0.4;
angAcc = (1.0 / INERTIA) * torque;
}
// update rotational velocity
angVel.add(timeInterval * angAcc);
// set a threshold on the rotational velocity term
const double MAX_ANG_VEL = 10.0;
double vel = angVel.length();
if (vel > MAX_ANG_VEL)
{
angAcc.mul(MAX_ANG_VEL / vel);
}
// add some damping too
const double DAMPING = 0.1;
angVel.mul(1.0 - DAMPING * timeInterval);
// if user switch is pressed, set velocity to zero
if (tool->getUserSwitch(0) == 1)
{
angVel.zero();
}
// compute the next rotation configuration of the object
if (angVel.length() > C_SMALL)
{
object->rotateAboutGlobalAxisRad(cNormalize(angVel), timeInterval * angVel.length());
}
}
// exit haptics thread
simulationFinished = true;
}
//===========================================================================
bool cEffectMagnet::computeForce(const cVector3d& a_toolPos,
const cVector3d& a_toolVel,
const unsigned int& a_toolID,
cVector3d& a_reactionForce)
{
// compute distance from object to tool
double distance = cDistance(a_toolPos, m_parent->m_interactionProjectedPoint);
// get parameters of magnet
double magnetMaxForce = m_parent->m_material.getMagnetMaxForce();
double magnetMaxDistance = m_parent->m_material.getMagnetMaxDistance();
double stiffness = m_parent->m_material.getStiffness();
double forceMagnitude = 0;
if ((distance > 0) && (distance < magnetMaxDistance) && (stiffness > 0))
{
double limitLinearModel = magnetMaxForce / stiffness;
cClamp(limitLinearModel, 0.0, 0.5 * distance);
if (distance < limitLinearModel)
{
// apply local linear model near magnet
forceMagnitude = stiffness * distance;
}
else
{
// compute quadratic model
cMatrix3d sys;
sys.m[0][0] = limitLinearModel * limitLinearModel;
sys.m[0][1] = limitLinearModel;
sys.m[0][2] = 1.0;
sys.m[1][0] = magnetMaxDistance * magnetMaxDistance;
sys.m[1][1] = magnetMaxDistance;
sys.m[1][2] = 1.0;
sys.m[2][0] = 2.0 * limitLinearModel;
sys.m[2][1] = 1.0;
sys.m[2][2] = 0.0;
sys.invert();
cVector3d param;
sys.mulr(cVector3d(magnetMaxForce, 0.0, -1.0), param);
// apply quadratic model
double val = distance - limitLinearModel;
forceMagnitude = param.x * val * val + param.y * val + param.z;
}
// compute magnetic force
a_reactionForce = cMul(forceMagnitude, cNormalize(cSub(m_parent->m_interactionProjectedPoint, a_toolPos)));
// add damping component
double viscosity = m_parent->m_material.getViscosity();
cVector3d viscousForce = cMul(-viscosity, a_toolVel);
a_reactionForce.add(viscousForce);
return (true);
}
else
{
// the tool is located outside the magnet zone
a_reactionForce.zero();
return (false);
}
}
void updateHaptics(void)
{
// reset clock
simClock.reset();
// main haptic simulation loop
while(simulationRunning)
{
// compute global reference frames for each object
world->computeGlobalPositions(true);
// update position and orientation of tool
tool->updatePose();
// compute interaction forces
tool->computeInteractionForces();
// send forces to device
tool->applyForces();
// stop the simulation clock
simClock.stop();
// read the time increment in seconds
double timeInterval = simClock.getCurrentTimeSeconds();
// restart the simulation clock
simClock.reset();
simClock.start();
// temp variable to compute rotational acceleration
cVector3d rotAcc(0,0,0);
// check if tool is touching an object
cGenericObject* objectContact = tool->m_proxyPointForceModel->m_contactPoint0->m_object;
if (objectContact != NULL)
{
// retrieve the root of the object mesh
cGenericObject* obj = objectContact->getSuperParent();
// get position of cursor in global coordinates
cVector3d toolPos = tool->m_deviceGlobalPos;
// get position of object in global coordinates
cVector3d objectPos = obj->getGlobalPos();
// compute a vector from the center of mass of the object (point of rotation) to the tool
cVector3d vObjectCMToTool = cSub(toolPos, objectPos);
// compute acceleration based on the interaction forces
// between the tool and the object
if (vObjectCMToTool.length() > 0.0)
{
// get the last force applied to the cursor in global coordinates
// we negate the result to obtain the opposite force that is applied on the
// object
cVector3d toolForce = cNegate(tool->m_lastComputedGlobalForce);
// compute effective force to take into account the fact the object
// can only rotate around a its center mass and not translate
cVector3d effectiveForce = toolForce - cProject(toolForce, vObjectCMToTool);
// compute the resulting torque
cVector3d torque = cMul(vObjectCMToTool.length(), cCross( cNormalize(vObjectCMToTool), effectiveForce));
// update rotational acceleration
const double OBJECT_INERTIA = 0.4;
rotAcc = (1.0 / OBJECT_INERTIA) * torque;
}
}
// update rotational velocity
rotVel.add(timeInterval * rotAcc);
// set a threshold on the rotational velocity term
const double ROT_VEL_MAX = 10.0;
double velMag = rotVel.length();
if (velMag > ROT_VEL_MAX)
{
rotVel.mul(ROT_VEL_MAX / velMag);
}
// add some damping too
const double DAMPING_GAIN = 0.1;
rotVel.mul(1.0 - DAMPING_GAIN * timeInterval);
// if user switch is pressed, set velocity to zero
if (tool->getUserSwitch(0) == 1)
{
rotVel.zero();
}
// compute the next rotation configuration of the object
if (rotVel.length() > CHAI_SMALL)
{
object->rotate(cNormalize(rotVel), timeInterval * rotVel.length());
}
}
// exit haptics thread
simulationFinished = true;
}
