godot/servers/physics/joints/generic_6dof_joint_sw.cpp

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/*  generic_6dof_joint_sw.cpp                                            */
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/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2017 Godot Engine contributors (cf. AUTHORS.md)    */
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/*
Adapted to Godot from the Bullet library.
See corresponding header file for licensing info.
*/

#include "generic_6dof_joint_sw.h"

#define GENERIC_D6_DISABLE_WARMSTARTING 1

//////////////////////////// G6DOFRotationalLimitMotorSW ////////////////////////////////////

int G6DOFRotationalLimitMotorSW::testLimitValue(real_t test_value) {
	if (m_loLimit > m_hiLimit) {
		m_currentLimit = 0; //Free from violation
		return 0;
	}

	if (test_value < m_loLimit) {
		m_currentLimit = 1; //low limit violation
		m_currentLimitError = test_value - m_loLimit;
		return 1;
	} else if (test_value > m_hiLimit) {
		m_currentLimit = 2; //High limit violation
		m_currentLimitError = test_value - m_hiLimit;
		return 2;
	};

	m_currentLimit = 0; //Free from violation
	return 0;
}

real_t G6DOFRotationalLimitMotorSW::solveAngularLimits(
		real_t timeStep, Vector3 &axis, real_t jacDiagABInv,
		BodySW *body0, BodySW *body1) {
	if (needApplyTorques() == false) return 0.0f;

	real_t target_velocity = m_targetVelocity;
	real_t maxMotorForce = m_maxMotorForce;

	//current error correction
	if (m_currentLimit != 0) {
		target_velocity = -m_ERP * m_currentLimitError / (timeStep);
		maxMotorForce = m_maxLimitForce;
	}

	maxMotorForce *= timeStep;

	// current velocity difference
	Vector3 vel_diff = body0->get_angular_velocity();
	if (body1) {
		vel_diff -= body1->get_angular_velocity();
	}

	real_t rel_vel = axis.dot(vel_diff);

	// correction velocity
	real_t motor_relvel = m_limitSoftness * (target_velocity - m_damping * rel_vel);

	if (motor_relvel < CMP_EPSILON && motor_relvel > -CMP_EPSILON) {
		return 0.0f; //no need for applying force
	}

	// correction impulse
	real_t unclippedMotorImpulse = (1 + m_bounce) * motor_relvel * jacDiagABInv;

	// clip correction impulse
	real_t clippedMotorImpulse;

	///@todo: should clip against accumulated impulse
	if (unclippedMotorImpulse > 0.0f) {
		clippedMotorImpulse = unclippedMotorImpulse > maxMotorForce ? maxMotorForce : unclippedMotorImpulse;
	} else {
		clippedMotorImpulse = unclippedMotorImpulse < -maxMotorForce ? -maxMotorForce : unclippedMotorImpulse;
	}

	// sort with accumulated impulses
	real_t lo = real_t(-1e30);
	real_t hi = real_t(1e30);

	real_t oldaccumImpulse = m_accumulatedImpulse;
	real_t sum = oldaccumImpulse + clippedMotorImpulse;
	m_accumulatedImpulse = sum > hi ? real_t(0.) : sum < lo ? real_t(0.) : sum;

	clippedMotorImpulse = m_accumulatedImpulse - oldaccumImpulse;

	Vector3 motorImp = clippedMotorImpulse * axis;

	body0->apply_torque_impulse(motorImp);
	if (body1) body1->apply_torque_impulse(-motorImp);

	return clippedMotorImpulse;
}

//////////////////////////// End G6DOFRotationalLimitMotorSW ////////////////////////////////////

//////////////////////////// G6DOFTranslationalLimitMotorSW ////////////////////////////////////
real_t G6DOFTranslationalLimitMotorSW::solveLinearAxis(
		real_t timeStep,
		real_t jacDiagABInv,
		BodySW *body1, const Vector3 &pointInA,
		BodySW *body2, const Vector3 &pointInB,
		int limit_index,
		const Vector3 &axis_normal_on_a,
		const Vector3 &anchorPos) {

	///find relative velocity
	//    Vector3 rel_pos1 = pointInA - body1->get_transform().origin;
	//    Vector3 rel_pos2 = pointInB - body2->get_transform().origin;
	Vector3 rel_pos1 = anchorPos - body1->get_transform().origin;
	Vector3 rel_pos2 = anchorPos - body2->get_transform().origin;

	Vector3 vel1 = body1->get_velocity_in_local_point(rel_pos1);
	Vector3 vel2 = body2->get_velocity_in_local_point(rel_pos2);
	Vector3 vel = vel1 - vel2;

	real_t rel_vel = axis_normal_on_a.dot(vel);

	/// apply displacement correction

	//positional error (zeroth order error)
	real_t depth = -(pointInA - pointInB).dot(axis_normal_on_a);
	real_t lo = real_t(-1e30);
	real_t hi = real_t(1e30);

	real_t minLimit = m_lowerLimit[limit_index];
	real_t maxLimit = m_upperLimit[limit_index];

	//handle the limits
	if (minLimit < maxLimit) {
		{
			if (depth > maxLimit) {
				depth -= maxLimit;
				lo = real_t(0.);

			} else {
				if (depth < minLimit) {
					depth -= minLimit;
					hi = real_t(0.);
				} else {
					return 0.0f;
				}
			}
		}
	}

	real_t normalImpulse = m_limitSoftness[limit_index] * (m_restitution[limit_index] * depth / timeStep - m_damping[limit_index] * rel_vel) * jacDiagABInv;

	real_t oldNormalImpulse = m_accumulatedImpulse[limit_index];
	real_t sum = oldNormalImpulse + normalImpulse;
	m_accumulatedImpulse[limit_index] = sum > hi ? real_t(0.) : sum < lo ? real_t(0.) : sum;
	normalImpulse = m_accumulatedImpulse[limit_index] - oldNormalImpulse;

	Vector3 impulse_vector = axis_normal_on_a * normalImpulse;
	body1->apply_impulse(rel_pos1, impulse_vector);
	body2->apply_impulse(rel_pos2, -impulse_vector);
	return normalImpulse;
}

//////////////////////////// G6DOFTranslationalLimitMotorSW ////////////////////////////////////

Generic6DOFJointSW::Generic6DOFJointSW(BodySW *rbA, BodySW *rbB, const Transform &frameInA, const Transform &frameInB, bool useLinearReferenceFrameA)
	: JointSW(_arr, 2), m_frameInA(frameInA), m_frameInB(frameInB),
	  m_useLinearReferenceFrameA(useLinearReferenceFrameA) {
	A = rbA;
	B = rbB;
	A->add_constraint(this, 0);
	B->add_constraint(this, 1);
}

void Generic6DOFJointSW::calculateAngleInfo() {
	Basis relative_frame = m_calculatedTransformA.basis.inverse() * m_calculatedTransformB.basis;

	m_calculatedAxisAngleDiff = relative_frame.get_euler();

	// in euler angle mode we do not actually constrain the angular velocity
	// along the axes axis[0] and axis[2] (although we do use axis[1]) :
	//
	//    to get			constrain w2-w1 along		...not
	//    ------			---------------------		------
	//    d(angle[0])/dt = 0	ax[1] x ax[2]			ax[0]
	//    d(angle[1])/dt = 0	ax[1]
	//    d(angle[2])/dt = 0	ax[0] x ax[1]			ax[2]
	//
	// constraining w2-w1 along an axis 'a' means that a'*(w2-w1)=0.
	// to prove the result for angle[0], write the expression for angle[0] from
	// GetInfo1 then take the derivative. to prove this for angle[2] it is
	// easier to take the euler rate expression for d(angle[2])/dt with respect
	// to the components of w and set that to 0.

	Vector3 axis0 = m_calculatedTransformB.basis.get_axis(0);
	Vector3 axis2 = m_calculatedTransformA.basis.get_axis(2);

	m_calculatedAxis[1] = axis2.cross(axis0);
	m_calculatedAxis[0] = m_calculatedAxis[1].cross(axis2);
	m_calculatedAxis[2] = axis0.cross(m_calculatedAxis[1]);

	/*
	if(m_debugDrawer)
	{

		char buff[300];
		sprintf(buff,"\n X: %.2f ; Y: %.2f ; Z: %.2f ",
		m_calculatedAxisAngleDiff[0],
		m_calculatedAxisAngleDiff[1],
		m_calculatedAxisAngleDiff[2]);
		m_debugDrawer->reportErrorWarning(buff);
	}
	*/
}

void Generic6DOFJointSW::calculateTransforms() {
	m_calculatedTransformA = A->get_transform() * m_frameInA;
	m_calculatedTransformB = B->get_transform() * m_frameInB;

	calculateAngleInfo();
}

void Generic6DOFJointSW::buildLinearJacobian(
		JacobianEntrySW &jacLinear, const Vector3 &normalWorld,
		const Vector3 &pivotAInW, const Vector3 &pivotBInW) {
	memnew_placement(&jacLinear, JacobianEntrySW(
										 A->get_principal_inertia_axes().transposed(),
										 B->get_principal_inertia_axes().transposed(),
										 pivotAInW - A->get_transform().origin - A->get_center_of_mass(),
										 pivotBInW - B->get_transform().origin - B->get_center_of_mass(),
										 normalWorld,
										 A->get_inv_inertia(),
										 A->get_inv_mass(),
										 B->get_inv_inertia(),
										 B->get_inv_mass()));
}

void Generic6DOFJointSW::buildAngularJacobian(
		JacobianEntrySW &jacAngular, const Vector3 &jointAxisW) {
	memnew_placement(&jacAngular, JacobianEntrySW(jointAxisW,
										  A->get_principal_inertia_axes().transposed(),
										  B->get_principal_inertia_axes().transposed(),
										  A->get_inv_inertia(),
										  B->get_inv_inertia()));
}

bool Generic6DOFJointSW::testAngularLimitMotor(int axis_index) {
	real_t angle = m_calculatedAxisAngleDiff[axis_index];

	//test limits
	m_angularLimits[axis_index].testLimitValue(angle);
	return m_angularLimits[axis_index].needApplyTorques();
}

bool Generic6DOFJointSW::setup(real_t p_step) {

	// Clear accumulated impulses for the next simulation step
	m_linearLimits.m_accumulatedImpulse = Vector3(real_t(0.), real_t(0.), real_t(0.));
	int i;
	for (i = 0; i < 3; i++) {
		m_angularLimits[i].m_accumulatedImpulse = real_t(0.);
	}
	//calculates transform
	calculateTransforms();

	//  const Vector3& pivotAInW = m_calculatedTransformA.origin;
	//  const Vector3& pivotBInW = m_calculatedTransformB.origin;
	calcAnchorPos();
	Vector3 pivotAInW = m_AnchorPos;
	Vector3 pivotBInW = m_AnchorPos;

	// not used here
	//    Vector3 rel_pos1 = pivotAInW - A->get_transform().origin;
	//    Vector3 rel_pos2 = pivotBInW - B->get_transform().origin;

	Vector3 normalWorld;
	//linear part
	for (i = 0; i < 3; i++) {
		if (m_linearLimits.enable_limit[i] && m_linearLimits.isLimited(i)) {
			if (m_useLinearReferenceFrameA)
				normalWorld = m_calculatedTransformA.basis.get_axis(i);
			else
				normalWorld = m_calculatedTransformB.basis.get_axis(i);

			buildLinearJacobian(
					m_jacLinear[i], normalWorld,
					pivotAInW, pivotBInW);
		}
	}

	// angular part
	for (i = 0; i < 3; i++) {
		//calculates error angle
		if (m_angularLimits[i].m_enableLimit && testAngularLimitMotor(i)) {
			normalWorld = this->getAxis(i);
			// Create angular atom
			buildAngularJacobian(m_jacAng[i], normalWorld);
		}
	}

	return true;
}

void Generic6DOFJointSW::solve(real_t timeStep) {
	m_timeStep = timeStep;

	//calculateTransforms();

	int i;

	// linear

	Vector3 pointInA = m_calculatedTransformA.origin;
	Vector3 pointInB = m_calculatedTransformB.origin;

	real_t jacDiagABInv;
	Vector3 linear_axis;
	for (i = 0; i < 3; i++) {
		if (m_linearLimits.enable_limit[i] && m_linearLimits.isLimited(i)) {
			jacDiagABInv = real_t(1.) / m_jacLinear[i].getDiagonal();

			if (m_useLinearReferenceFrameA)
				linear_axis = m_calculatedTransformA.basis.get_axis(i);
			else
				linear_axis = m_calculatedTransformB.basis.get_axis(i);

			m_linearLimits.solveLinearAxis(
					m_timeStep,
					jacDiagABInv,
					A, pointInA,
					B, pointInB,
					i, linear_axis, m_AnchorPos);
		}
	}

	// angular
	Vector3 angular_axis;
	real_t angularJacDiagABInv;
	for (i = 0; i < 3; i++) {
		if (m_angularLimits[i].m_enableLimit && m_angularLimits[i].needApplyTorques()) {

			// get axis
			angular_axis = getAxis(i);

			angularJacDiagABInv = real_t(1.) / m_jacAng[i].getDiagonal();

			m_angularLimits[i].solveAngularLimits(m_timeStep, angular_axis, angularJacDiagABInv, A, B);
		}
	}
}

void Generic6DOFJointSW::updateRHS(real_t timeStep) {
	(void)timeStep;
}

Vector3 Generic6DOFJointSW::getAxis(int axis_index) const {
	return m_calculatedAxis[axis_index];
}

real_t Generic6DOFJointSW::getAngle(int axis_index) const {
	return m_calculatedAxisAngleDiff[axis_index];
}

void Generic6DOFJointSW::calcAnchorPos(void) {
	real_t imA = A->get_inv_mass();
	real_t imB = B->get_inv_mass();
	real_t weight;
	if (imB == real_t(0.0)) {
		weight = real_t(1.0);
	} else {
		weight = imA / (imA + imB);
	}
	const Vector3 &pA = m_calculatedTransformA.origin;
	const Vector3 &pB = m_calculatedTransformB.origin;
	m_AnchorPos = pA * weight + pB * (real_t(1.0) - weight);
	return;
} // Generic6DOFJointSW::calcAnchorPos()

void Generic6DOFJointSW::set_param(Vector3::Axis p_axis, PhysicsServer::G6DOFJointAxisParam p_param, real_t p_value) {

	ERR_FAIL_INDEX(p_axis, 3);
	switch (p_param) {
		case PhysicsServer::G6DOF_JOINT_LINEAR_LOWER_LIMIT: {

			m_linearLimits.m_lowerLimit[p_axis] = p_value;
		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_UPPER_LIMIT: {

			m_linearLimits.m_upperLimit[p_axis] = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_LIMIT_SOFTNESS: {

			m_linearLimits.m_limitSoftness[p_axis] = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_RESTITUTION: {

			m_linearLimits.m_restitution[p_axis] = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_DAMPING: {

			m_linearLimits.m_damping[p_axis] = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_LOWER_LIMIT: {

			m_angularLimits[p_axis].m_loLimit = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_UPPER_LIMIT: {

			m_angularLimits[p_axis].m_hiLimit = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_LIMIT_SOFTNESS: {

			m_angularLimits[p_axis].m_limitSoftness = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_DAMPING: {

			m_angularLimits[p_axis].m_damping = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_RESTITUTION: {

			m_angularLimits[p_axis].m_bounce = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_FORCE_LIMIT: {

			m_angularLimits[p_axis].m_maxLimitForce = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_ERP: {

			m_angularLimits[p_axis].m_ERP = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_MOTOR_TARGET_VELOCITY: {

			m_angularLimits[p_axis].m_targetVelocity = p_value;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_MOTOR_FORCE_LIMIT: {

			m_angularLimits[p_axis].m_maxLimitForce = p_value;

		} break;
	}
}

real_t Generic6DOFJointSW::get_param(Vector3::Axis p_axis, PhysicsServer::G6DOFJointAxisParam p_param) const {
	ERR_FAIL_INDEX_V(p_axis, 3, 0);
	switch (p_param) {
		case PhysicsServer::G6DOF_JOINT_LINEAR_LOWER_LIMIT: {

			return m_linearLimits.m_lowerLimit[p_axis];
		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_UPPER_LIMIT: {

			return m_linearLimits.m_upperLimit[p_axis];

		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_LIMIT_SOFTNESS: {

			return m_linearLimits.m_limitSoftness[p_axis];

		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_RESTITUTION: {

			return m_linearLimits.m_restitution[p_axis];

		} break;
		case PhysicsServer::G6DOF_JOINT_LINEAR_DAMPING: {

			return m_linearLimits.m_damping[p_axis];

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_LOWER_LIMIT: {

			return m_angularLimits[p_axis].m_loLimit;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_UPPER_LIMIT: {

			return m_angularLimits[p_axis].m_hiLimit;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_LIMIT_SOFTNESS: {

			return m_angularLimits[p_axis].m_limitSoftness;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_DAMPING: {

			return m_angularLimits[p_axis].m_damping;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_RESTITUTION: {

			return m_angularLimits[p_axis].m_bounce;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_FORCE_LIMIT: {

			return m_angularLimits[p_axis].m_maxLimitForce;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_ERP: {

			return m_angularLimits[p_axis].m_ERP;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_MOTOR_TARGET_VELOCITY: {

			return m_angularLimits[p_axis].m_targetVelocity;

		} break;
		case PhysicsServer::G6DOF_JOINT_ANGULAR_MOTOR_FORCE_LIMIT: {

			return m_angularLimits[p_axis].m_maxMotorForce;

		} break;
	}
	return 0;
}

void Generic6DOFJointSW::set_flag(Vector3::Axis p_axis, PhysicsServer::G6DOFJointAxisFlag p_flag, bool p_value) {

	ERR_FAIL_INDEX(p_axis, 3);

	switch (p_flag) {
		case PhysicsServer::G6DOF_JOINT_FLAG_ENABLE_LINEAR_LIMIT: {

			m_linearLimits.enable_limit[p_axis] = p_value;
		} break;
		case PhysicsServer::G6DOF_JOINT_FLAG_ENABLE_ANGULAR_LIMIT: {

			m_angularLimits[p_axis].m_enableLimit = p_value;
		} break;
		case PhysicsServer::G6DOF_JOINT_FLAG_ENABLE_MOTOR: {

			m_angularLimits[p_axis].m_enableMotor = p_value;
		} break;
	}
}
bool Generic6DOFJointSW::get_flag(Vector3::Axis p_axis, PhysicsServer::G6DOFJointAxisFlag p_flag) const {

	ERR_FAIL_INDEX_V(p_axis, 3, 0);
	switch (p_flag) {
		case PhysicsServer::G6DOF_JOINT_FLAG_ENABLE_LINEAR_LIMIT: {

			return m_linearLimits.enable_limit[p_axis];
		} break;
		case PhysicsServer::G6DOF_JOINT_FLAG_ENABLE_ANGULAR_LIMIT: {

			return m_angularLimits[p_axis].m_enableLimit;
		} break;
		case PhysicsServer::G6DOF_JOINT_FLAG_ENABLE_MOTOR: {

			return m_angularLimits[p_axis].m_enableMotor;
		} break;
	}

	return 0;
}