set up deformable world and solver (does not support contact or friction yet)

src/BulletSoftBody/btDeformableRigidDynamicsWorld.cpp

@@ -0,0 +1,39 @@
+//
+//  btDeformableRigidDynamicsWorld.cpp
+//  BulletSoftBody
+//
+//  Created by Xuchen Han on 7/1/19.
+//
+
+#include <stdio.h>
+#include "btDeformableRigidDynamicsWorld.h"
+#include "btDeformableBodySolver.h"
+
+void btDeformableRigidDynamicsWorld::internalSingleStepSimulation(btScalar timeStep)
+{
+    // Let the solver grab the soft bodies and if necessary optimize for it
+    m_deformableBodySolver->optimize(getSoftDynamicsWorld()->getSoftBodyArray());
+    
+    if (!m_deformableBodySolver->checkInitialized())
+    {
+        btAssert("Solver initialization failed\n");
+    }
+    
+    btSoftRigidDynamicsWorld::btDiscreteDynamicsWorld::internalSingleStepSimulation(timeStep);
+    
+    ///solve deformable bodies constraints
+    solveDeformableBodiesConstraints(timeStep);
+
+    
+    ///update soft bodies
+    m_deformableBodySolver->updateSoftBodies();
+    
+    // End solver-wise simulation step
+    // ///////////////////////////////
+}
+
+void btDeformableRigidDynamicsWorld::solveDeformableBodiesConstraints(btScalar timeStep)
+{
+    m_deformableBodySolver->solveConstraints(timeStep);
+}
+