virtualx-engine/thirdparty/bullet/BulletDynamics/Vehicle/btWheelInfo.cpp

/*
 * Copyright (c) 2005 Erwin Coumans https://bulletphysics.org
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies.
 * Erwin Coumans makes no representations about the suitability 
 * of this software for any purpose.  
 * It is provided "as is" without express or implied warranty.
*/
#include "btWheelInfo.h"
#include "BulletDynamics/Dynamics/btRigidBody.h"  // for pointvelocity

btScalar btWheelInfo::getSuspensionRestLength() const
{
	return m_suspensionRestLength1;
}

void btWheelInfo::updateWheel(const btRigidBody& chassis, RaycastInfo& raycastInfo)
{
	(void)raycastInfo;

	if (m_raycastInfo.m_isInContact)

	{
		btScalar project = m_raycastInfo.m_contactNormalWS.dot(m_raycastInfo.m_wheelDirectionWS);
		btVector3 chassis_velocity_at_contactPoint;
		btVector3 relpos = m_raycastInfo.m_contactPointWS - chassis.getCenterOfMassPosition();
		chassis_velocity_at_contactPoint = chassis.getVelocityInLocalPoint(relpos);
		btScalar projVel = m_raycastInfo.m_contactNormalWS.dot(chassis_velocity_at_contactPoint);
		if (project >= btScalar(-0.1))
		{
			m_suspensionRelativeVelocity = btScalar(0.0);
			m_clippedInvContactDotSuspension = btScalar(1.0) / btScalar(0.1);
		}
		else
		{
			btScalar inv = btScalar(-1.) / project;
			m_suspensionRelativeVelocity = projVel * inv;
			m_clippedInvContactDotSuspension = inv;
		}
	}

	else  // Not in contact : position wheel in a nice (rest length) position
	{
		m_raycastInfo.m_suspensionLength = this->getSuspensionRestLength();
		m_suspensionRelativeVelocity = btScalar(0.0);
		m_raycastInfo.m_contactNormalWS = -m_raycastInfo.m_wheelDirectionWS;
		m_clippedInvContactDotSuspension = btScalar(1.0);
	}
}