add options to toggle between whether line search is used & add more documentation

src/BulletSoftBody/btDeformableBodySolver.cpp

@@ -429,3 +429,8 @@ void btDeformableBodySolver::setImplicit(bool implicit)
     m_implicit = implicit;
     m_objective->setImplicit(implicit);
 }
+
+void btDeformableBodySolver::setLineSearch(bool lineSearch)
+{
+    m_lineSearch = lineSearch;
+}

src/BulletSoftBody/btDeformableBodySolver.h

@@ -103,16 +103,38 @@ public:
     
     virtual bool checkInitialized(){return true;}
     
+    // If true, implicit time stepping scheme is used.
+    // Otherwise, explicit time stepping scheme is used
     void setImplicit(bool implicit);
     
+    // If true, newton's method with line search is used when implicit time stepping scheme is turned on
+    void setLineSearch(bool lineSearch);
+    
+    // set temporary position x^* = x_n + dt * v
+    // update the deformation gradient at position x^*
     void updateState();
     
+    // set dv = dv + scale * ddv
     void updateDv(btScalar scale = 1);
     
+    // set temporary position x^* = x_n + dt * v^*
     void updateTempPosition();
+    
+    // save the current dv to m_backup_dv;
     void backupDv();
+    
+    // set dv to the backed-up value
     void revertDv();
+    
+    // set dv = dv + scale * ddv
+    // set v^* = v_n + dv
+    // set temporary position x^* = x_n + dt * v^*
+    // update the deformation gradient at position x^*
     void updateEnergy(btScalar scale);
+    
+    // calculates the appropriately scaled kinetic energy in the system, which is
+    // 1/2 * dv^T * M * dv
+    // used in line search
     btScalar kineticEnergy();
 };
 

src/BulletSoftBody/btDeformableMultiBodyDynamicsWorld.cpp

@@ -69,14 +69,14 @@ void btDeformableMultiBodyDynamicsWorld::internalSingleStepSimulation(btScalar t
     // End solver-wise simulation step
     // ///////////////////////////////
 }
-
+//
 //void btDeformableMultiBodyDynamicsWorld::positionCorrection(btScalar timeStep)
 //{
-//    // perform position correction for all constraints 
+//    // perform position correction for all constraints
 //    BT_PROFILE("positionCorrection");
-//    for (int index = 0; index < m_deformableBodySolver->m_objective->projection.m_constraints.size(); ++index)
+//    for (int index = 0; index < m_deformableBodySolver->m_objective->m_projection.m_constraints.size(); ++index)
 //    {
-//        DeformableContactConstraint& constraint = *m_deformableBodySolver->m_objective->projection.m_constraints.getAtIndex(index);
+//        DeformableContactConstraint& constraint = *m_deformableBodySolver->m_objective->m_projection.m_constraints.getAtIndex(index);
 //        for (int j = 0; j < constraint.m_contact.size(); ++j)
 //        {
 //            const btSoftBody::RContact* c = constraint.m_contact[j];
@@ -144,16 +144,11 @@ void btDeformableMultiBodyDynamicsWorld::internalSingleStepSimulation(btScalar t
 //    }
 //}
 
-void btDeformableMultiBodyDynamicsWorld::positionCorrection(btScalar timeStep)
-{
-}
-
-
 void btDeformableMultiBodyDynamicsWorld::integrateTransforms(btScalar timeStep)
 {
     BT_PROFILE("integrateTransforms");
     //m_deformableBodySolver->backupVelocity();
-    //positionCorrection(timeStep);
+    //positionCorrection(timeStep);  // looks like position correction is no longer necessary
     btMultiBodyDynamicsWorld::integrateTransforms(timeStep);
     for (int i = 0; i < m_softBodies.size(); ++i)
     {
@@ -329,6 +324,7 @@ void btDeformableMultiBodyDynamicsWorld::reinitialize(btScalar timeStep)
 {
     m_internalTime += timeStep;
     m_deformableBodySolver->setImplicit(m_implicit);
+    m_deformableBodySolver->setLineSearch(m_lineSearch);
     m_deformableBodySolver->reinitialize(m_softBodies, timeStep);
     btDispatcherInfo& dispatchInfo = btMultiBodyDynamicsWorld::getDispatchInfo();
     dispatchInfo.m_timeStep = timeStep;

src/BulletSoftBody/btDeformableMultiBodyDynamicsWorld.h

@@ -47,6 +47,7 @@ class btDeformableMultiBodyDynamicsWorld : public btMultiBodyDynamicsWorld
     btScalar m_internalTime;
     int m_contact_iterations;
     bool m_implicit;
+    bool m_lineSearch;
     
     typedef void (*btSolverCallback)(btScalar time, btDeformableMultiBodyDynamicsWorld* world);
     btSolverCallback m_solverCallback;
@@ -159,6 +160,11 @@ public:
     {
         m_implicit = implicit;
     }
+    
+    void setLineSearch(bool lineSearch)
+    {
+        m_lineSearch = lineSearch;
+    }
 };
 
 #endif  //BT_DEFORMABLE_MULTIBODY_DYNAMICS_WORLD_H