text: /*
  Bullet Continuous Collision Detection and Physics Library
  Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/
  
  This software is provided 'as-is', without any express or implied warranty.
  In no event will the authors be held liable for any damages arising from the use of this software.
  Permission is granted to anyone to use this software for any purpose, 
  including commercial applications, and to alter it and redistribute it freely, 
  subject to the following restrictions:
  
  1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
  */
  
  #include "btSphereBoxCollisionAlgorithm.h"
  #include "BulletCollision/CollisionDispatch/btCollisionDispatcher.h"
  #include "BulletCollision/CollisionShapes/btSphereShape.h"
  #include "BulletCollision/CollisionShapes/btBoxShape.h"
  #include "BulletCollision/CollisionDispatch/btCollisionObject.h"
  //#include <stdio.h>
  
  btSphereBoxCollisionAlgorithm::btSphereBoxCollisionAlgorithm(btPersistentManifold* mf,const btCollisionAlgorithmConstructionInfo& ci,btCollisionObject* col0,btCollisionObject* col1, bool isSwapped)
  : btActivatingCollisionAlgorithm(ci,col0,col1),
  m_ownManifold(false),
  m_manifoldPtr(mf),
  m_isSwapped(isSwapped)
  {
  	btCollisionObject* sphereObj = m_isSwapped? col1 : col0;
  	btCollisionObject* boxObj = m_isSwapped? col0 : col1;
  	
  	if (!m_manifoldPtr && m_dispatcher->needsCollision(sphereObj,boxObj))
  	{
  		m_manifoldPtr = m_dispatcher->getNewManifold(sphereObj,boxObj);
  		m_ownManifold = true;
  	}
  }
  
  
  btSphereBoxCollisionAlgorithm::~btSphereBoxCollisionAlgorithm()
  {
  	if (m_ownManifold)
  	{
  		if (m_manifoldPtr)
  			m_dispatcher->releaseManifold(m_manifoldPtr);
  	}
  }
  
  
  
  void btSphereBoxCollisionAlgorithm::processCollision (btCollisionObject* body0,btCollisionObject* body1,const btDispatcherInfo& dispatchInfo,btManifoldResult* resultOut)
  {
  	(void)dispatchInfo;
  	(void)resultOut;
  	if (!m_manifoldPtr)
  		return;
  
  	btCollisionObject* sphereObj = m_isSwapped? body1 : body0;
  	btCollisionObject* boxObj = m_isSwapped? body0 : body1;
  
  
  	btSphereShape* sphere0 = (btSphereShape*)sphereObj->getCollisionShape();
  
  	btVector3 normalOnSurfaceB;
  	btVector3 pOnBox,pOnSphere;
  	btVector3 sphereCenter = sphereObj->getWorldTransform().getOrigin();
  	btScalar radius = sphere0->getRadius();
  	
  	btScalar dist = getSphereDistance(boxObj,pOnBox,pOnSphere,sphereCenter,radius);
  
  	resultOut->setPersistentManifold(m_manifoldPtr);
  
  	if (dist < SIMD_EPSILON)
  	{
  		btVector3 normalOnSurfaceB = (pOnBox- pOnSphere).normalize();
  
  		/// report a contact. internally this will be kept persistent, and contact reduction is done
  
  		resultOut->addContactPoint(normalOnSurfaceB,pOnBox,dist);
  		
  	}
  
  	if (m_ownManifold)
  	{
  		if (m_manifoldPtr->getNumContacts())
  		{
  			resultOut->refreshContactPoints();
  		}
  	}
  
  }
  
  btScalar btSphereBoxCollisionAlgorithm::calculateTimeOfImpact(btCollisionObject* col0,btCollisionObject* col1,const btDispatcherInfo& dispatchInfo,btManifoldResult* resultOut)
  {
  	(void)resultOut;
  	(void)dispatchInfo;
  	(void)col0;
  	(void)col1;
  
  	//not yet
  	return btScalar(1.);
  }
  
  
  btScalar btSphereBoxCollisionAlgorithm::getSphereDistance(btCollisionObject* boxObj, btVector3& pointOnBox, btVector3& v3PointOnSphere, const btVector3& sphereCenter, btScalar fRadius ) 
  {
  
  	btScalar margins;
  	btVector3 bounds[2];
  	btBoxShape* boxShape= (btBoxShape*)boxObj->getCollisionShape();
  	
  	bounds[0] = -boxShape->getHalfExtentsWithoutMargin();
  	bounds[1] = boxShape->getHalfExtentsWithoutMargin();
  
  	margins = boxShape->getMargin();//also add sphereShape margin?
  
  	const btTransform&	m44T = boxObj->getWorldTransform();
  
  	btVector3	boundsVec[2];
  	btScalar	fPenetration;
  
  	boundsVec[0] = bounds[0];
  	boundsVec[1] = bounds[1];
  
  	btVector3	marginsVec( margins, margins, margins );
  
  	// add margins
  	bounds[0] += marginsVec;
  	bounds[1] -= marginsVec;
  
  	/////////////////////////////////////////////////
  
  	btVector3	tmp, prel, n[6], normal, v3P;
  	btScalar   fSep = btScalar(10000000.0), fSepThis;
  
  	n[0].setValue( btScalar(-1.0),  btScalar(0.0),  btScalar(0.0) );
  	n[1].setValue(  btScalar(0.0), btScalar(-1.0),  btScalar(0.0) );
  	n[2].setValue(  btScalar(0.0),  btScalar(0.0), btScalar(-1.0) );
  	n[3].setValue(  btScalar(1.0),  btScalar(0.0),  btScalar(0.0) );
  	n[4].setValue(  btScalar(0.0),  btScalar(1.0),  btScalar(0.0) );
  	n[5].setValue(  btScalar(0.0),  btScalar(0.0),  btScalar(1.0) );
  
  	// convert  point in local space
  	prel = m44T.invXform( sphereCenter);
  	
  	bool	bFound = false;
  
  	v3P = prel;
  
  	for (int i=0;i<6;i++)
  	{
  		int j = i<3? 0:1;
  		if ( (fSepThis = ((v3P-bounds[j]) .dot(n[i]))) > btScalar(0.0) )
  		{
  			v3P = v3P - n[i]*fSepThis;		
  			bFound = true;
  		}
  	}
  	
  	//
  
  	if ( bFound )
  	{
  		bounds[0] = boundsVec[0];
  		bounds[1] = boundsVec[1];
  
  		normal = (prel - v3P).normalize();
  		pointOnBox = v3P + normal*margins;
  		v3PointOnSphere = prel - normal*fRadius;
  
  		if ( ((v3PointOnSphere - pointOnBox) .dot (normal)) > btScalar(0.0) )
  		{
  			return btScalar(1.0);
  		}
  
  		// transform back in world space
  		tmp = m44T( pointOnBox);
  		pointOnBox    = tmp;
  		tmp  = m44T( v3PointOnSphere);		
  		v3PointOnSphere = tmp;
  		btScalar fSeps2 = (pointOnBox-v3PointOnSphere).length2();
  		
  		//if this fails, fallback into deeper penetration case, below
  		if (fSeps2 > SIMD_EPSILON)
  		{
  			fSep = - btSqrt(fSeps2);
  			normal = (pointOnBox-v3PointOnSphere);
  			normal *= btScalar(1.)/fSep;
  		}
  
  		return fSep;
  	}
  
  	//////////////////////////////////////////////////
  	// Deep penetration case
  
  	fPenetration = getSpherePenetration( boxObj,pointOnBox, v3PointOnSphere, sphereCenter, fRadius,bounds[0],bounds[1] );
  
  	bounds[0] = boundsVec[0];
  	bounds[1] = boundsVec[1];
  
  	if ( fPenetration <= btScalar(0.0) )
  		return (fPenetration-margins);
  	else
  		return btScalar(1.0);
  }
  
  btScalar btSphereBoxCollisionAlgorithm::getSpherePenetration( btCollisionObject* boxObj,btVector3& pointOnBox, btVector3& v3PointOnSphere, const btVector3& sphereCenter, btScalar fRadius, const btVector3& aabbMin, const btVector3& aabbMax) 
  {
  
  	btVector3 bounds[2];
  
  	bounds[0] = aabbMin;
  	bounds[1] = aabbMax;
  
  	btVector3	p0, tmp, prel, n[6], normal;
  	btScalar   fSep = btScalar(-10000000.0), fSepThis;
  
  	// set p0 and normal to a default value to shup up GCC
  	p0.setValue(btScalar(0.), btScalar(0.), btScalar(0.));
  	normal.setValue(btScalar(0.), btScalar(0.), btScalar(0.));
  
  	n[0].setValue( btScalar(-1.0),  btScalar(0.0),  btScalar(0.0) );
  	n[1].setValue(  btScalar(0.0), btScalar(-1.0),  btScalar(0.0) );
  	n[2].setValue(  btScalar(0.0),  btScalar(0.0), btScalar(-1.0) );
  	n[3].setValue(  btScalar(1.0),  btScalar(0.0),  btScalar(0.0) );
  	n[4].setValue(  btScalar(0.0),  btScalar(1.0),  btScalar(0.0) );
  	n[5].setValue(  btScalar(0.0),  btScalar(0.0),  btScalar(1.0) );
  
  	const btTransform&	m44T = boxObj->getWorldTransform();
  
  	// convert  point in local space
  	prel = m44T.invXform( sphereCenter);
  
  	///////////
  
  	for (int i=0;i<6;i++)
  	{
  		int j = i<3 ? 0:1;
  		if ( (fSepThis = ((prel-bounds[j]) .dot( n[i]))-fRadius) > btScalar(0.0) )	return btScalar(1.0);
  		if ( fSepThis > fSep )
  		{
  			p0 = bounds[j];	normal = (btVector3&)n[i];
  			fSep = fSepThis;
  		}
  	}
  
  	pointOnBox = prel - normal*(normal.dot((prel-p0)));
  	v3PointOnSphere = pointOnBox + normal*fSep;
  
  	// transform back in world space
  	tmp  = m44T( pointOnBox);		
  	pointOnBox    = tmp;
  	tmp  = m44T( v3PointOnSphere);		v3PointOnSphere = tmp;
  	normal = (pointOnBox-v3PointOnSphere).normalize();
  
  	return fSep;
  
  }
  
  