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btSequentialImpulseConstraintSolver.cpp

/*
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 "btSequentialImpulseConstraintSolver.h"
#include "BulletCollision/NarrowPhaseCollision/btPersistentManifold.h"
#include "BulletDynamics/Dynamics/btRigidBody.h"
#include "btContactConstraint.h"
#include "btSolve2LinearConstraint.h"
#include "btContactSolverInfo.h"
#include "LinearMath/btIDebugDraw.h"
#include "btJacobianEntry.h"
#include "LinearMath/btMinMax.h"
#include "BulletDynamics/ConstraintSolver/btTypedConstraint.h"
#include <new>
#include "LinearMath/btStackAlloc.h"
#include "LinearMath/btQuickprof.h"
#include "btSolverBody.h"
#include "btSolverConstraint.h"

#include "LinearMath/btAlignedObjectArray.h"

#ifdef USE_PROFILE
#include "LinearMath/btQuickprof.h"
#endif //USE_PROFILE

int totalCpd = 0;

int   gTotalContactPoints = 0;

struct      btOrderIndex
{
      int   m_manifoldIndex;
      int   m_pointIndex;
};



#define SEQUENTIAL_IMPULSE_MAX_SOLVER_POINTS 16384
static btOrderIndex     gOrder[SEQUENTIAL_IMPULSE_MAX_SOLVER_POINTS];


unsigned long btSequentialImpulseConstraintSolver::btRand2()
{
  m_btSeed2 = (1664525L*m_btSeed2 + 1013904223L) & 0xffffffff;
  return m_btSeed2;
}



//See ODE: adam's all-int straightforward(?) dRandInt (0..n-1)
int btSequentialImpulseConstraintSolver::btRandInt2 (int n)
{
  // seems good; xor-fold and modulus
  const unsigned long un = n;
  unsigned long r = btRand2();

  // note: probably more aggressive than it needs to be -- might be
  //       able to get away without one or two of the innermost branches.
  if (un <= 0x00010000UL) {
    r ^= (r >> 16);
    if (un <= 0x00000100UL) {
      r ^= (r >> 8);
      if (un <= 0x00000010UL) {
        r ^= (r >> 4);
        if (un <= 0x00000004UL) {
          r ^= (r >> 2);
          if (un <= 0x00000002UL) {
            r ^= (r >> 1);
          }
        }
     }
    }
   }

  return (int) (r % un);
}





bool  MyContactDestroyedCallback(void* userPersistentData)
{
      assert (userPersistentData);
      btConstraintPersistentData* cpd = (btConstraintPersistentData*)userPersistentData;
      delete cpd;
      totalCpd--;
      //printf("totalCpd = %i. DELETED Ptr %x\n",totalCpd,userPersistentData);
      return true;
}



btSequentialImpulseConstraintSolver::btSequentialImpulseConstraintSolver()
:m_solverMode(SOLVER_RANDMIZE_ORDER | SOLVER_CACHE_FRIENDLY), //not using SOLVER_USE_WARMSTARTING,
m_btSeed2(0)
{
      gContactDestroyedCallback = &MyContactDestroyedCallback;

      //initialize default friction/contact funcs
      int i,j;
      for (i=0;i<MAX_CONTACT_SOLVER_TYPES;i++)
            for (j=0;j<MAX_CONTACT_SOLVER_TYPES;j++)
            {

                  m_contactDispatch[i][j] = resolveSingleCollision;
                  m_frictionDispatch[i][j] = resolveSingleFriction;
            }
}


void  initSolverBody(btSolverBody* solverBody, btRigidBody* rigidbody)
{
/*    int size = sizeof(btSolverBody);
      int sizeofrb = sizeof(btRigidBody);
      int sizemanifold = sizeof(btPersistentManifold);
      int sizeofmp = sizeof(btManifoldPoint);
      int sizeofPersistData = sizeof (btConstraintPersistentData);
*/

      solverBody->m_angularVelocity = rigidbody->getAngularVelocity();
      solverBody->m_centerOfMassPosition = rigidbody->getCenterOfMassPosition();
      solverBody->m_friction = rigidbody->getFriction();
//    solverBody->m_invInertiaWorld = rigidbody->getInvInertiaTensorWorld();
      solverBody->m_invMass = rigidbody->getInvMass();
      solverBody->m_linearVelocity = rigidbody->getLinearVelocity();
      solverBody->m_originalBody = rigidbody;
      solverBody->m_angularFactor = rigidbody->getAngularFactor();
}

btScalar penetrationResolveFactor = btScalar(0.9);
btScalar restitutionCurve(btScalar rel_vel, btScalar restitution)
{
      btScalar rest = restitution * -rel_vel;
      return rest;
}






//velocity + friction
//response  between two dynamic objects with friction
SIMD_FORCE_INLINE btScalar resolveSingleCollisionCombinedCacheFriendly(
      btSolverBody& body1,
      btSolverBody& body2,
      btSolverConstraint& contactConstraint,
      const btContactSolverInfo& solverInfo)
{
      (void)solverInfo;

      btScalar normalImpulse(0.f);
      {
            if (contactConstraint.m_penetration < 0.f)
                  return 0.f;

      //  Optimized version of projected relative velocity, use precomputed cross products with normal
      //    body1.getVelocityInLocalPoint(contactConstraint.m_rel_posA,vel1);
      //    body2.getVelocityInLocalPoint(contactConstraint.m_rel_posB,vel2);
      //    btVector3 vel = vel1 - vel2;
      //    btScalar  rel_vel = contactConstraint.m_contactNormal.dot(vel);

            btScalar rel_vel;
            btScalar vel1Dotn = contactConstraint.m_contactNormal.dot(body1.m_linearVelocity) 
                              + contactConstraint.m_relpos1CrossNormal.dot(body1.m_angularVelocity);
            btScalar vel2Dotn = contactConstraint.m_contactNormal.dot(body2.m_linearVelocity) 
                              + contactConstraint.m_relpos2CrossNormal.dot(body2.m_angularVelocity);

            rel_vel = vel1Dotn-vel2Dotn;


            btScalar positionalError = contactConstraint.m_penetration;
            btScalar velocityError = contactConstraint.m_restitution - rel_vel;// * damping;

            btScalar penetrationImpulse = positionalError * contactConstraint.m_jacDiagABInv;
            btScalar    velocityImpulse = velocityError * contactConstraint.m_jacDiagABInv;
            btScalar normalImpulse = penetrationImpulse+velocityImpulse;
            
            // See Erin Catto's GDC 2006 paper: Clamp the accumulated impulse
            btScalar oldNormalImpulse = contactConstraint.m_appliedImpulse;
            btScalar sum = oldNormalImpulse + normalImpulse;
            contactConstraint.m_appliedImpulse = btScalar(0.) > sum ? btScalar(0.): sum;

            btScalar oldVelocityImpulse = contactConstraint.m_appliedVelocityImpulse;
            btScalar velocitySum = oldVelocityImpulse + velocityImpulse;
            contactConstraint.m_appliedVelocityImpulse = btScalar(0.) > velocitySum ? btScalar(0.): velocitySum;

            normalImpulse = contactConstraint.m_appliedImpulse - oldNormalImpulse;

            if (body1.m_invMass)
            {
                  body1.internalApplyImpulse(contactConstraint.m_contactNormal*body1.m_invMass,
                        contactConstraint.m_angularComponentA,normalImpulse);
            }
            if (body2.m_invMass)
            {
                  body2.internalApplyImpulse(contactConstraint.m_contactNormal*body2.m_invMass,
                        contactConstraint.m_angularComponentB,-normalImpulse);
            }

      }

      

      return normalImpulse;
}


#ifndef NO_FRICTION_TANGENTIALS

SIMD_FORCE_INLINE btScalar resolveSingleFrictionCacheFriendly(
      btSolverBody& body1,
      btSolverBody& body2,
      btSolverConstraint& contactConstraint,
      const btContactSolverInfo& solverInfo,
      btScalar appliedNormalImpulse)
{
      (void)solverInfo;

      
      const btScalar combinedFriction = contactConstraint.m_friction;
      
      const btScalar limit = appliedNormalImpulse * combinedFriction;
      
      if (appliedNormalImpulse>btScalar(0.))
      //friction
      {
            
            btScalar j1;
            {

                  btScalar rel_vel;
                  const btScalar vel1Dotn = contactConstraint.m_contactNormal.dot(body1.m_linearVelocity) 
                                    + contactConstraint.m_relpos1CrossNormal.dot(body1.m_angularVelocity);
                  const btScalar vel2Dotn = contactConstraint.m_contactNormal.dot(body2.m_linearVelocity) 
                        + contactConstraint.m_relpos2CrossNormal.dot(body2.m_angularVelocity);
                  rel_vel = vel1Dotn-vel2Dotn;

                  // calculate j that moves us to zero relative velocity
                  j1 = -rel_vel * contactConstraint.m_jacDiagABInv;
                  btScalar oldTangentImpulse = contactConstraint.m_appliedImpulse;
                  contactConstraint.m_appliedImpulse = oldTangentImpulse + j1;
                  GEN_set_min(contactConstraint.m_appliedImpulse, limit);
                  GEN_set_max(contactConstraint.m_appliedImpulse, -limit);
                  j1 = contactConstraint.m_appliedImpulse - oldTangentImpulse;

            }
      
            if (body1.m_invMass)
            {
                  body1.internalApplyImpulse(contactConstraint.m_contactNormal*body1.m_invMass,contactConstraint.m_angularComponentA,j1);
            }
            if (body2.m_invMass)
            {
                  body2.internalApplyImpulse(contactConstraint.m_contactNormal*body2.m_invMass,contactConstraint.m_angularComponentB,-j1);
            }

      } 
      return 0.f;
}


#else

//velocity + friction
//response  between two dynamic objects with friction
btScalar resolveSingleFrictionCacheFriendly(
      btSolverBody& body1,
      btSolverBody& body2,
      btSolverConstraint& contactConstraint,
      const btContactSolverInfo& solverInfo)
{

      btVector3 vel1;
      btVector3 vel2;
      btScalar normalImpulse(0.f);

      {
            const btVector3& normal = contactConstraint.m_contactNormal;
            if (contactConstraint.m_penetration < 0.f)
                  return 0.f;


            body1.getVelocityInLocalPoint(contactConstraint.m_rel_posA,vel1);
            body2.getVelocityInLocalPoint(contactConstraint.m_rel_posB,vel2);
            btVector3 vel = vel1 - vel2;
            btScalar rel_vel;
            rel_vel = normal.dot(vel);

            btVector3 lat_vel = vel - normal * rel_vel;
            btScalar lat_rel_vel = lat_vel.length2();

            btScalar combinedFriction = contactConstraint.m_friction;
            const btVector3& rel_pos1 = contactConstraint.m_rel_posA;
            const btVector3& rel_pos2 = contactConstraint.m_rel_posB;


            //if (contactConstraint.m_appliedVelocityImpulse > 0.f)
            if (lat_rel_vel > SIMD_EPSILON*SIMD_EPSILON)
            {
                  lat_rel_vel = btSqrt(lat_rel_vel);

                  lat_vel /= lat_rel_vel;
                  btVector3 temp1 = body1.m_invInertiaWorld * rel_pos1.cross(lat_vel);
                  btVector3 temp2 = body2.m_invInertiaWorld * rel_pos2.cross(lat_vel);
                  btScalar friction_impulse = lat_rel_vel /
                        (body1.m_invMass + body2.m_invMass + lat_vel.dot(temp1.cross(rel_pos1) + temp2.cross(rel_pos2)));
                  btScalar normal_impulse = contactConstraint.m_appliedVelocityImpulse * combinedFriction;

                  GEN_set_min(friction_impulse, normal_impulse);
                  GEN_set_max(friction_impulse, -normal_impulse);
                  body1.applyImpulse(lat_vel * -friction_impulse, rel_pos1);
                  body2.applyImpulse(lat_vel * friction_impulse, rel_pos2);
            }
      }

      return normalImpulse;
}

#endif //NO_FRICTION_TANGENTIALS

btAlignedObjectArray<btSolverBody>  tmpSolverBodyPool;
btAlignedObjectArray<btSolverConstraint>  tmpSolverConstraintPool;
btAlignedObjectArray<btSolverConstraint>  tmpSolverFrictionConstraintPool;


00341 btScalar btSequentialImpulseConstraintSolver::solveGroupCacheFriendly(btCollisionObject** bodies,int numBodies,btPersistentManifold** manifoldPtr, int numManifolds,btTypedConstraint** constraints,int numConstraints,const btContactSolverInfo& infoGlobal,btIDebugDraw* debugDrawer,btStackAlloc* stackAlloc)
{
      (void)stackAlloc;
      (void)debugDrawer;

      if (!(numConstraints + numManifolds))
      {
//          printf("empty\n");
            return 0.f;
      }

      BEGIN_PROFILE("refreshManifolds");

      int i;
      for (i=0;i<numManifolds;i++)
      {
            btPersistentManifold* manifold = manifoldPtr[i];
            btRigidBody* rb0 = (btRigidBody*)manifold->getBody0();
            btRigidBody* rb1 = (btRigidBody*)manifold->getBody1();

            manifold->refreshContactPoints(rb0->getCenterOfMassTransform(),rb1->getCenterOfMassTransform());

      }
      
      END_PROFILE("refreshManifolds");


      BEGIN_PROFILE("gatherSolverData");

      //int sizeofSB = sizeof(btSolverBody);
      //int sizeofSC = sizeof(btSolverConstraint);


      //if (1)
      {
            //if m_stackAlloc, try to pack bodies/constraints to speed up solving
//          btBlock*                            sablock;
//          sablock = stackAlloc->beginBlock();

      //    int memsize = 16;
//          unsigned char* stackMemory = stackAlloc->allocate(memsize);

            
            //todo: use stack allocator for this temp memory
            int minReservation = numManifolds*2;

            tmpSolverBodyPool.reserve(minReservation);

            {
                  for (int i=0;i<numBodies;i++)
                  {
                        btRigidBody* rb = btRigidBody::upcast(bodies[i]);
                        if (rb &&   (rb->getIslandTag() >= 0))
                        {
                              btAssert(rb->getCompanionId() < 0);
                              int solverBodyId = tmpSolverBodyPool.size();
                              btSolverBody& solverBody = tmpSolverBodyPool.expand();
                              initSolverBody(&solverBody,rb);
                              rb->setCompanionId(solverBodyId);
                        } 
                  }
            }

            
            tmpSolverConstraintPool.reserve(minReservation);
            tmpSolverFrictionConstraintPool.reserve(minReservation);
            {
                  int i;

                  for (i=0;i<numManifolds;i++)
                  {
                        btPersistentManifold* manifold = manifoldPtr[i];
                        btRigidBody* rb0 = (btRigidBody*)manifold->getBody0();
                        btRigidBody* rb1 = (btRigidBody*)manifold->getBody1();

                  
                        int solverBodyIdA=-1;
                        int solverBodyIdB=-1;

                        if (manifold->getNumContacts())
                        {

                              

                              if (rb0->getIslandTag() >= 0)
                              {
                                    solverBodyIdA = rb0->getCompanionId();
                              } else
                              {
                                    //create a static body
                                    solverBodyIdA = tmpSolverBodyPool.size();
                                    btSolverBody& solverBody = tmpSolverBodyPool.expand();
                                    initSolverBody(&solverBody,rb0);
                              }

                              if (rb1->getIslandTag() >= 0)
                              {
                                    solverBodyIdB = rb1->getCompanionId();
                              } else
                              {
                                    //create a static body
                                    solverBodyIdB = tmpSolverBodyPool.size();
                                    btSolverBody& solverBody = tmpSolverBodyPool.expand();
                                    initSolverBody(&solverBody,rb1);
                              }
                        }

                        for (int j=0;j<manifold->getNumContacts();j++)
                        {
                              
                              btManifoldPoint& cp = manifold->getContactPoint(j);

                              int frictionIndex = tmpSolverConstraintPool.size();

                              if (cp.getDistance() <= btScalar(0.))
                              {
                                    
                                    const btVector3& pos1 = cp.getPositionWorldOnA();
                                    const btVector3& pos2 = cp.getPositionWorldOnB();

                                    btVector3 rel_pos1 = pos1 - rb0->getCenterOfMassPosition(); 
                                    btVector3 rel_pos2 = pos2 - rb1->getCenterOfMassPosition();

                                    
                                          btScalar relaxation = 1.f;

                                    {
                                          btSolverConstraint& solverConstraint = tmpSolverConstraintPool.expand();

                                          solverConstraint.m_solverBodyIdA = solverBodyIdA;
                                          solverConstraint.m_solverBodyIdB = solverBodyIdB;
                                          solverConstraint.m_constraintType = btSolverConstraint::BT_SOLVER_CONTACT_1D;

                              

                                          {
                                                //can be optimized, the cross products are already calculated
                                                btScalar denom0 = rb0->computeImpulseDenominator(pos1,cp.m_normalWorldOnB);
                                                btScalar denom1 = rb1->computeImpulseDenominator(pos2,cp.m_normalWorldOnB);
                                                btScalar denom = relaxation/(denom0+denom1);
                                                solverConstraint.m_jacDiagABInv = denom;
                                          }

                                          solverConstraint.m_contactNormal = cp.m_normalWorldOnB;
                                          solverConstraint.m_relpos1CrossNormal = rel_pos1.cross(cp.m_normalWorldOnB);
                                          solverConstraint.m_relpos2CrossNormal = rel_pos2.cross(cp.m_normalWorldOnB);


                                          btVector3 vel1 = rb0->getVelocityInLocalPoint(rel_pos1);
                                          btVector3 vel2 = rb1->getVelocityInLocalPoint(rel_pos2);
                        
                                          btVector3 vel = vel1 - vel2;
                                          btScalar rel_vel;
                                          rel_vel = cp.m_normalWorldOnB.dot(vel);
                                          

                                          solverConstraint.m_penetration = cp.getDistance();///btScalar(infoGlobal.m_numIterations);
                                          solverConstraint.m_friction = cp.m_combinedFriction;
                                          btScalar rest =  restitutionCurve(rel_vel, cp.m_combinedRestitution);
                                          if (rest <= btScalar(0.))
                                          {
                                                rest = 0.f;
                                          };
                                          
                                          btScalar penVel = -solverConstraint.m_penetration/infoGlobal.m_timeStep;
                                          if (rest > penVel)
                                          {
                                                rest = btScalar(0.);
                                          }
                                          solverConstraint.m_restitution = rest;

                                          solverConstraint.m_penetration *= -(infoGlobal.m_erp/infoGlobal.m_timeStep);

                                          solverConstraint.m_appliedImpulse = 0.f;
                                          solverConstraint.m_appliedVelocityImpulse = 0.f;
                                          
                              
                                          btVector3 torqueAxis0 = rel_pos1.cross(cp.m_normalWorldOnB);
                                          solverConstraint.m_angularComponentA = rb0->getInvInertiaTensorWorld()*torqueAxis0;
                                          btVector3 torqueAxis1 = rel_pos2.cross(cp.m_normalWorldOnB);            
                                          solverConstraint.m_angularComponentB = rb1->getInvInertiaTensorWorld()*torqueAxis1;
                                    }

                                    //create 2 '1d axis' constraints for 2 tangential friction directions
                  
                                    //re-calculate friction direction every frame, todo: check if this is really needed
                                    btVector3 frictionTangential0a, frictionTangential1b;

                                    btPlaneSpace1(cp.m_normalWorldOnB,frictionTangential0a,frictionTangential1b);

                                    {
                                          btSolverConstraint& solverConstraint = tmpSolverFrictionConstraintPool.expand();
                                          solverConstraint.m_contactNormal = frictionTangential0a;

                                          solverConstraint.m_solverBodyIdA = solverBodyIdA;
                                          solverConstraint.m_solverBodyIdB = solverBodyIdB;
                                          solverConstraint.m_constraintType = btSolverConstraint::BT_SOLVER_FRICTION_1D;
                                          solverConstraint.m_frictionIndex = frictionIndex;

                                          solverConstraint.m_friction = cp.m_combinedFriction;

                                          solverConstraint.m_appliedImpulse = btScalar(0.);
                                          solverConstraint.m_appliedVelocityImpulse = 0.f;

                                          btScalar denom0 = rb0->computeImpulseDenominator(pos1,solverConstraint.m_contactNormal);
                                          btScalar denom1 = rb1->computeImpulseDenominator(pos2,solverConstraint.m_contactNormal);
                                          btScalar denom = relaxation/(denom0+denom1);
                                          solverConstraint.m_jacDiagABInv = denom;

                                          {
                                          btVector3 ftorqueAxis0 = rel_pos1.cross(solverConstraint.m_contactNormal);
                                          solverConstraint.m_relpos1CrossNormal = ftorqueAxis0;
                                          solverConstraint.m_angularComponentA = rb0->getInvInertiaTensorWorld()*ftorqueAxis0;
                                          }
                                          {
                                          btVector3 ftorqueAxis0 = rel_pos2.cross(solverConstraint.m_contactNormal);
                                          solverConstraint.m_relpos2CrossNormal = ftorqueAxis0;
                                          solverConstraint.m_angularComponentB = rb1->getInvInertiaTensorWorld()*ftorqueAxis0;
                                          }

                                    }


                                    {

                                          btSolverConstraint& solverConstraint = tmpSolverFrictionConstraintPool.expand();
                                          solverConstraint.m_contactNormal = frictionTangential1b;

                                          solverConstraint.m_solverBodyIdA = solverBodyIdA;
                                          solverConstraint.m_solverBodyIdB = solverBodyIdB;
                                          solverConstraint.m_constraintType = btSolverConstraint::BT_SOLVER_FRICTION_1D;
                                          solverConstraint.m_frictionIndex = frictionIndex;

                                          solverConstraint.m_friction = cp.m_combinedFriction;

                                          solverConstraint.m_appliedImpulse = btScalar(0.);
                                          solverConstraint.m_appliedVelocityImpulse = 0.f;
                                    
                                          btScalar denom0 = rb0->computeImpulseDenominator(pos1,solverConstraint.m_contactNormal);
                                          btScalar denom1 = rb1->computeImpulseDenominator(pos2,solverConstraint.m_contactNormal);
                                          btScalar denom = relaxation/(denom0+denom1);
                                          solverConstraint.m_jacDiagABInv = denom;
                                          {
                                                btVector3 ftorqueAxis1 = rel_pos1.cross(solverConstraint.m_contactNormal);
                                                solverConstraint.m_relpos1CrossNormal = ftorqueAxis1;
                                                solverConstraint.m_angularComponentA = rb0->getInvInertiaTensorWorld()*ftorqueAxis1;
                                                }
                                          {
                                                btVector3 ftorqueAxis1 = rel_pos2.cross(solverConstraint.m_contactNormal);
                                                solverConstraint.m_relpos2CrossNormal = ftorqueAxis1;
                                                solverConstraint.m_angularComponentB = rb1->getInvInertiaTensorWorld()*ftorqueAxis1;
                                                }
                                          }

                              }
                        }
                  }
            }
      }
      END_PROFILE("gatherSolverData");

      BEGIN_PROFILE("prepareConstraints");

      btContactSolverInfo info = infoGlobal;

      {
            int j;
            for (j=0;j<numConstraints;j++)
            {
                  btTypedConstraint* constraint = constraints[j];
                  constraint->buildJacobian();
            }
      }
      
      btAlignedObjectArray<int>     gOrderTmpConstraintPool;
      btAlignedObjectArray<int>     gOrderFrictionConstraintPool;

      int numConstraintPool = tmpSolverConstraintPool.size();
      int numFrictionPool = tmpSolverFrictionConstraintPool.size();

      ///todo: use stack allocator for such temporarily memory, same for solver bodies/constraints
      gOrderTmpConstraintPool.resize(numConstraintPool);
      gOrderFrictionConstraintPool.resize(numFrictionPool);
      {
            int i;
            for (i=0;i<numConstraintPool;i++)
            {
                  gOrderTmpConstraintPool[i] = i;
            }
            for (i=0;i<numFrictionPool;i++)
            {
                  gOrderFrictionConstraintPool[i] = i;
            }
      }




      END_PROFILE("prepareConstraints");


      BEGIN_PROFILE("solveConstraints");

      //should traverse the contacts random order...
      int iteration;
      {
            for ( iteration = 0;iteration<info.m_numIterations;iteration++)
            {                 

                  int j;
                  if (m_solverMode & SOLVER_RANDMIZE_ORDER)
                  {
                        if ((iteration & 7) == 0) {
                              for (j=0; j<numConstraintPool; ++j) {
                                    int tmp = gOrderTmpConstraintPool[j];
                                    int swapi = btRandInt2(j+1);
                                    gOrderTmpConstraintPool[j] = gOrderTmpConstraintPool[swapi];
                                    gOrderTmpConstraintPool[swapi] = tmp;
                              }

                              for (j=0; j<numFrictionPool; ++j) {
                                    int tmp = gOrderFrictionConstraintPool[j];
                                    int swapi = btRandInt2(j+1);
                                    gOrderFrictionConstraintPool[j] = gOrderFrictionConstraintPool[swapi];
                                    gOrderFrictionConstraintPool[swapi] = tmp;
                              }
                        }
                  }

                  for (j=0;j<numConstraints;j++)
                  {
                        btTypedConstraint* constraint = constraints[j];
                        ///todo: use solver bodies, so we don't need to copy from/to btRigidBody

                        if ((constraint->getRigidBodyA().getIslandTag() >= 0) && (constraint->getRigidBodyA().getCompanionId() >= 0))
                        {
                              tmpSolverBodyPool[constraint->getRigidBodyA().getCompanionId()].writebackVelocity();
                        }
                        if ((constraint->getRigidBodyB().getIslandTag() >= 0) && (constraint->getRigidBodyB().getCompanionId() >= 0))
                        {
                              tmpSolverBodyPool[constraint->getRigidBodyB().getCompanionId()].writebackVelocity();
                        }

                        constraint->solveConstraint(info.m_timeStep);

                        if ((constraint->getRigidBodyA().getIslandTag() >= 0) && (constraint->getRigidBodyA().getCompanionId() >= 0))
                        {
                              tmpSolverBodyPool[constraint->getRigidBodyA().getCompanionId()].readVelocity();
                        }
                        if ((constraint->getRigidBodyB().getIslandTag() >= 0) && (constraint->getRigidBodyB().getCompanionId() >= 0))
                        {
                              tmpSolverBodyPool[constraint->getRigidBodyB().getCompanionId()].readVelocity();
                        }

                  }

                  {
                        int numPoolConstraints = tmpSolverConstraintPool.size();
                        for (j=0;j<numPoolConstraints;j++)
                        {
                              btSolverConstraint& solveManifold = tmpSolverConstraintPool[gOrderTmpConstraintPool[j]];
                              resolveSingleCollisionCombinedCacheFriendly(tmpSolverBodyPool[solveManifold.m_solverBodyIdA],
                                    tmpSolverBodyPool[solveManifold.m_solverBodyIdB],solveManifold,info);
                        }
                  }

                  {
                         int numFrictionPoolConstraints = tmpSolverFrictionConstraintPool.size();
                        for (j=0;j<numFrictionPoolConstraints;j++)
                        {
                              btSolverConstraint& solveManifold = tmpSolverFrictionConstraintPool[gOrderFrictionConstraintPool[j]];
                                    btScalar appliedNormalImpulse = tmpSolverConstraintPool[solveManifold.m_frictionIndex].m_appliedImpulse;

                                    resolveSingleFrictionCacheFriendly(tmpSolverBodyPool[solveManifold.m_solverBodyIdA],
                                          tmpSolverBodyPool[solveManifold.m_solverBodyIdB],solveManifold,info,appliedNormalImpulse);
                        }
                  }
                  


            }
      }
            
      for ( i=0;i<tmpSolverBodyPool.size();i++)
      {
            tmpSolverBodyPool[i].writebackVelocity();
      }

      END_PROFILE("solveConstraints");

//    printf("tmpSolverConstraintPool.size() = %i\n",tmpSolverConstraintPool.size());

/*
      printf("tmpSolverBodyPool.size() = %i\n",tmpSolverBodyPool.size());
      printf("tmpSolverConstraintPool.size() = %i\n",tmpSolverConstraintPool.size());
      printf("tmpSolverFrictionConstraintPool.size() = %i\n",tmpSolverFrictionConstraintPool.size());

      
      printf("tmpSolverBodyPool.capacity() = %i\n",tmpSolverBodyPool.capacity());
      printf("tmpSolverConstraintPool.capacity() = %i\n",tmpSolverConstraintPool.capacity());
      printf("tmpSolverFrictionConstraintPool.capacity() = %i\n",tmpSolverFrictionConstraintPool.capacity());
*/

      tmpSolverBodyPool.resize(0);
      tmpSolverConstraintPool.resize(0);
      tmpSolverFrictionConstraintPool.resize(0);


      return 0.f;
}

/// btSequentialImpulseConstraintSolver Sequentially applies impulses
00753 btScalar btSequentialImpulseConstraintSolver::solveGroup(btCollisionObject** bodies,int numBodies,btPersistentManifold** manifoldPtr, int numManifolds,btTypedConstraint** constraints,int numConstraints,const btContactSolverInfo& infoGlobal,btIDebugDraw* debugDrawer,btStackAlloc* stackAlloc)
{

      if (getSolverMode() & SOLVER_CACHE_FRIENDLY)
      {
            //you need to provide at least some bodies
            //btSimpleDynamicsWorld needs to switch off SOLVER_CACHE_FRIENDLY
            btAssert(bodies);
            btAssert(numBodies);
            return solveGroupCacheFriendly(bodies,numBodies,manifoldPtr, numManifolds,constraints,numConstraints,infoGlobal,debugDrawer,stackAlloc);
      }


      BEGIN_PROFILE("prepareConstraints");
      

      btContactSolverInfo info = infoGlobal;

      int numiter = infoGlobal.m_numIterations;
#ifdef USE_PROFILE
      btProfiler::beginBlock("solve");
#endif //USE_PROFILE

      int totalPoints = 0;


      {
            short j;
            for (j=0;j<numManifolds;j++)
            {
                  btPersistentManifold* manifold = manifoldPtr[j];
                  prepareConstraints(manifold,info,debugDrawer);

                  for (short p=0;p<manifoldPtr[j]->getNumContacts();p++)
                  {
                        gOrder[totalPoints].m_manifoldIndex = j;
                        gOrder[totalPoints].m_pointIndex = p;
                        totalPoints++;
                  }
            }
      }

      {
            int j;
            for (j=0;j<numConstraints;j++)
            {
                  btTypedConstraint* constraint = constraints[j];
                  constraint->buildJacobian();
            }
      }
      
      END_PROFILE("prepareConstraints");


      BEGIN_PROFILE("solveConstraints");

      //should traverse the contacts random order...
      int iteration;

      {
            for ( iteration = 0;iteration<numiter;iteration++)
            {
                  int j;
                  if (m_solverMode & SOLVER_RANDMIZE_ORDER)
                  {
                        if ((iteration & 7) == 0) {
                              for (j=0; j<totalPoints; ++j) {
                                    btOrderIndex tmp = gOrder[j];
                                    int swapi = btRandInt2(j+1);
                                    gOrder[j] = gOrder[swapi];
                                    gOrder[swapi] = tmp;
                              }
                        }
                  }

                  for (j=0;j<numConstraints;j++)
                  {
                        btTypedConstraint* constraint = constraints[j];
                        constraint->solveConstraint(info.m_timeStep);
                  }

                  for (j=0;j<totalPoints;j++)
                  {
                        btPersistentManifold* manifold = manifoldPtr[gOrder[j].m_manifoldIndex];
                        solve( (btRigidBody*)manifold->getBody0(),
                                                      (btRigidBody*)manifold->getBody1()
                        ,manifold->getContactPoint(gOrder[j].m_pointIndex),info,iteration,debugDrawer);
                  }
            
                  for (j=0;j<totalPoints;j++)
                  {
                        btPersistentManifold* manifold = manifoldPtr[gOrder[j].m_manifoldIndex];
                        solveFriction((btRigidBody*)manifold->getBody0(),
                              (btRigidBody*)manifold->getBody1(),manifold->getContactPoint(gOrder[j].m_pointIndex),info,iteration,debugDrawer);
                  }
            }
      }
            
      END_PROFILE("solveConstraints");


#ifdef USE_PROFILE
      btProfiler::endBlock("solve");
#endif //USE_PROFILE




      return btScalar(0.);
}







00870 void  btSequentialImpulseConstraintSolver::prepareConstraints(btPersistentManifold* manifoldPtr, const btContactSolverInfo& info,btIDebugDraw* debugDrawer)
{

      (void)debugDrawer;

      btRigidBody* body0 = (btRigidBody*)manifoldPtr->getBody0();
      btRigidBody* body1 = (btRigidBody*)manifoldPtr->getBody1();


      //only necessary to refresh the manifold once (first iteration). The integration is done outside the loop
      {
            manifoldPtr->refreshContactPoints(body0->getCenterOfMassTransform(),body1->getCenterOfMassTransform());
            
            int numpoints = manifoldPtr->getNumContacts();

            gTotalContactPoints += numpoints;

            btVector3 color(0,1,0);
            for (int i=0;i<numpoints ;i++)
            {
                  btManifoldPoint& cp = manifoldPtr->getContactPoint(i);
                  if (cp.getDistance() <= btScalar(0.))
                  {
                        const btVector3& pos1 = cp.getPositionWorldOnA();
                        const btVector3& pos2 = cp.getPositionWorldOnB();

                        btVector3 rel_pos1 = pos1 - body0->getCenterOfMassPosition(); 
                        btVector3 rel_pos2 = pos2 - body1->getCenterOfMassPosition();
                        

                        //this jacobian entry is re-used for all iterations
                        btJacobianEntry jac(body0->getCenterOfMassTransform().getBasis().transpose(),
                              body1->getCenterOfMassTransform().getBasis().transpose(),
                              rel_pos1,rel_pos2,cp.m_normalWorldOnB,body0->getInvInertiaDiagLocal(),body0->getInvMass(),
                              body1->getInvInertiaDiagLocal(),body1->getInvMass());

                        
                        btScalar jacDiagAB = jac.getDiagonal();

                        btConstraintPersistentData* cpd = (btConstraintPersistentData*) cp.m_userPersistentData;
                        if (cpd)
                        {
                              //might be invalid
                              cpd->m_persistentLifeTime++;
                              if (cpd->m_persistentLifeTime != cp.getLifeTime())
                              {
                                    //printf("Invalid: cpd->m_persistentLifeTime = %i cp.getLifeTime() = %i\n",cpd->m_persistentLifeTime,cp.getLifeTime());
                                    new (cpd) btConstraintPersistentData;
                                    cpd->m_persistentLifeTime = cp.getLifeTime();

                              } else
                              {
                                    //printf("Persistent: cpd->m_persistentLifeTime = %i cp.getLifeTime() = %i\n",cpd->m_persistentLifeTime,cp.getLifeTime());
                                    
                              }
                        } else
                        {
                                    
                              cpd = new btConstraintPersistentData;
                              assert(cpd);

                              totalCpd ++;
                              //printf("totalCpd = %i Created Ptr %x\n",totalCpd,cpd);
                              cp.m_userPersistentData = cpd;
                              cpd->m_persistentLifeTime = cp.getLifeTime();
                              //printf("CREATED: %x . cpd->m_persistentLifeTime = %i cp.getLifeTime() = %i\n",cpd,cpd->m_persistentLifeTime,cp.getLifeTime());
                              
                        }
                        assert(cpd);

                        cpd->m_jacDiagABInv = btScalar(1.) / jacDiagAB;

                        //Dependent on Rigidbody A and B types, fetch the contact/friction response func
                        //perhaps do a similar thing for friction/restutution combiner funcs...
                        
                        cpd->m_frictionSolverFunc = m_frictionDispatch[body0->m_frictionSolverType][body1->m_frictionSolverType];
                        cpd->m_contactSolverFunc = m_contactDispatch[body0->m_contactSolverType][body1->m_contactSolverType];
                        
                        btVector3 vel1 = body0->getVelocityInLocalPoint(rel_pos1);
                        btVector3 vel2 = body1->getVelocityInLocalPoint(rel_pos2);
                        btVector3 vel = vel1 - vel2;
                        btScalar rel_vel;
                        rel_vel = cp.m_normalWorldOnB.dot(vel);
                        
                        btScalar combinedRestitution = cp.m_combinedRestitution;
                        
                        cpd->m_penetration = cp.getDistance();///btScalar(info.m_numIterations);
                        cpd->m_friction = cp.m_combinedFriction;
                        cpd->m_restitution = restitutionCurve(rel_vel, combinedRestitution);
                        if (cpd->m_restitution <= btScalar(0.))
                        {
                              cpd->m_restitution = btScalar(0.0);

                        };
                        
                        //restitution and penetration work in same direction so
                        //rel_vel 
                        
                        btScalar penVel = -cpd->m_penetration/info.m_timeStep;

                        if (cpd->m_restitution > penVel)
                        {
                              cpd->m_penetration = btScalar(0.);
                        }                       
                        
                        

                        btScalar relaxation = info.m_damping;
                        if (m_solverMode & SOLVER_USE_WARMSTARTING)
                        {
                              cpd->m_appliedImpulse *= relaxation;
                        } else
                        {
                              cpd->m_appliedImpulse =btScalar(0.);
                        }
      
                        //for friction
                        cpd->m_prevAppliedImpulse = cpd->m_appliedImpulse;
                        
                        //re-calculate friction direction every frame, todo: check if this is really needed
                        btPlaneSpace1(cp.m_normalWorldOnB,cpd->m_frictionWorldTangential0,cpd->m_frictionWorldTangential1);


#define NO_FRICTION_WARMSTART 1

      #ifdef NO_FRICTION_WARMSTART
                        cpd->m_accumulatedTangentImpulse0 = btScalar(0.);
                        cpd->m_accumulatedTangentImpulse1 = btScalar(0.);
      #endif //NO_FRICTION_WARMSTART
                        btScalar denom0 = body0->computeImpulseDenominator(pos1,cpd->m_frictionWorldTangential0);
                        btScalar denom1 = body1->computeImpulseDenominator(pos2,cpd->m_frictionWorldTangential0);
                        btScalar denom = relaxation/(denom0+denom1);
                        cpd->m_jacDiagABInvTangent0 = denom;


                        denom0 = body0->computeImpulseDenominator(pos1,cpd->m_frictionWorldTangential1);
                        denom1 = body1->computeImpulseDenominator(pos2,cpd->m_frictionWorldTangential1);
                        denom = relaxation/(denom0+denom1);
                        cpd->m_jacDiagABInvTangent1 = denom;

                        btVector3 totalImpulse = 
      #ifndef NO_FRICTION_WARMSTART
                              cpd->m_frictionWorldTangential0*cpd->m_accumulatedTangentImpulse0+
                              cpd->m_frictionWorldTangential1*cpd->m_accumulatedTangentImpulse1+
      #endif //NO_FRICTION_WARMSTART
                              cp.m_normalWorldOnB*cpd->m_appliedImpulse;



                        ///
                        {
                        btVector3 torqueAxis0 = rel_pos1.cross(cp.m_normalWorldOnB);
                        cpd->m_angularComponentA = body0->getInvInertiaTensorWorld()*torqueAxis0;
                        btVector3 torqueAxis1 = rel_pos2.cross(cp.m_normalWorldOnB);            
                        cpd->m_angularComponentB = body1->getInvInertiaTensorWorld()*torqueAxis1;
                        }
                        {
                              btVector3 ftorqueAxis0 = rel_pos1.cross(cpd->m_frictionWorldTangential0);
                              cpd->m_frictionAngularComponent0A = body0->getInvInertiaTensorWorld()*ftorqueAxis0;
                        }
                        {
                              btVector3 ftorqueAxis1 = rel_pos1.cross(cpd->m_frictionWorldTangential1);
                              cpd->m_frictionAngularComponent1A = body0->getInvInertiaTensorWorld()*ftorqueAxis1;
                        }
                        {
                              btVector3 ftorqueAxis0 = rel_pos2.cross(cpd->m_frictionWorldTangential0);
                              cpd->m_frictionAngularComponent0B = body1->getInvInertiaTensorWorld()*ftorqueAxis0;
                        }
                        {
                              btVector3 ftorqueAxis1 = rel_pos2.cross(cpd->m_frictionWorldTangential1);
                              cpd->m_frictionAngularComponent1B = body1->getInvInertiaTensorWorld()*ftorqueAxis1;
                        }
                        
                        ///



                        //apply previous frames impulse on both bodies
                        body0->applyImpulse(totalImpulse, rel_pos1);
                        body1->applyImpulse(-totalImpulse, rel_pos2);
                  }
                  
            }
      }
}


btScalar btSequentialImpulseConstraintSolver::solveCombinedContactFriction(btRigidBody* body0,btRigidBody* body1, btManifoldPoint& cp, const btContactSolverInfo& info,int iter,btIDebugDraw* debugDrawer)
{
      btScalar maxImpulse = btScalar(0.);

      {

            btVector3 color(0,1,0);
            {
                  if (cp.getDistance() <= btScalar(0.))
                  {

                        if (iter == 0)
                        {
                              if (debugDrawer)
                                    debugDrawer->drawContactPoint(cp.m_positionWorldOnB,cp.m_normalWorldOnB,cp.getDistance(),cp.getLifeTime(),color);
                        }

                        {

                              //btConstraintPersistentData* cpd = (btConstraintPersistentData*) cp.m_userPersistentData;
                              btScalar impulse = resolveSingleCollisionCombined(
                                    *body0,*body1,
                                    cp,
                                    info);

                              if (maxImpulse < impulse)
                                    maxImpulse  = impulse;

                        }
                  }
            }
      }
      return maxImpulse;
}



btScalar btSequentialImpulseConstraintSolver::solve(btRigidBody* body0,btRigidBody* body1, btManifoldPoint& cp, const btContactSolverInfo& info,int iter,btIDebugDraw* debugDrawer)
{

      btScalar maxImpulse = btScalar(0.);

      {

            btVector3 color(0,1,0);
            {
                  if (cp.getDistance() <= btScalar(0.))
                  {

                        if (iter == 0)
                        {
                              if (debugDrawer)
                                    debugDrawer->drawContactPoint(cp.m_positionWorldOnB,cp.m_normalWorldOnB,cp.getDistance(),cp.getLifeTime(),color);
                        }

                        {

                              btConstraintPersistentData* cpd = (btConstraintPersistentData*) cp.m_userPersistentData;
                              btScalar impulse = cpd->m_contactSolverFunc(
                                    *body0,*body1,
                                    cp,
                                    info);

                              if (maxImpulse < impulse)
                                    maxImpulse  = impulse;

                        }
                  }
            }
      }
      return maxImpulse;
}

btScalar btSequentialImpulseConstraintSolver::solveFriction(btRigidBody* body0,btRigidBody* body1, btManifoldPoint& cp, const btContactSolverInfo& info,int iter,btIDebugDraw* debugDrawer)
{

      (void)debugDrawer;
      (void)iter;


      {

            btVector3 color(0,1,0);
            {
                  
                  if (cp.getDistance() <= btScalar(0.))
                  {

                        btConstraintPersistentData* cpd = (btConstraintPersistentData*) cp.m_userPersistentData;
                        cpd->m_frictionSolverFunc(
                              *body0,*body1,
                              cp,
                              info);

                        
                  }
            }

      
      }
      return btScalar(0.);
}

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