btWheelInfo.cpp

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/*
 * 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);
        }
}