prevent velocity of deformable from getting too big from explicit force

src/BulletSoftBody/btDeformableBodySolver.cpp

@@ -372,15 +372,26 @@ void btDeformableBodySolver::predictDeformableMotion(btSoftBody* psb, btScalar d
     psb->m_sst.velmrg = psb->m_sst.sdt * 3;
     psb->m_sst.radmrg = psb->getCollisionShape()->getMargin();
     psb->m_sst.updmrg = psb->m_sst.radmrg * (btScalar)0.25;
+    /* Bounds                */
+    psb->updateBounds();
+    
     /* Integrate            */
+    // do not allow particles to move more than 10% of the bounding box size
+    btScalar max_v = 0.1 * (psb->m_bounds[1]-psb->m_bounds[0]).norm() / dt;
     for (i = 0, ni = psb->m_nodes.size(); i < ni; ++i)
     {
         btSoftBody::Node& n = psb->m_nodes[i];
+        // apply drag
         n.m_v *= (1 - psb->m_cfg.drag);
+        // scale velocity back
+        if (n.m_v.norm() > max_v)
+        {
+            n.m_v.safeNormalize();
+            n.m_v *= max_v;
+        }
         n.m_q = n.m_x + n.m_v * dt;
     }
-    /* Bounds                */
+
-    psb->updateBounds();
     /* Nodes                */
     ATTRIBUTE_ALIGNED16(btDbvtVolume)
     vol;

src/BulletSoftBody/btSoftBody.cpp

@@ -2428,15 +2428,48 @@ void btSoftBody::updateBounds()
 		m_bounds[1] = btVector3(1000, 1000, 1000);
 
 	} else {*/
-	if (m_ndbvt.m_root)
+//    if (m_ndbvt.m_root)
+//    {
+//        const btVector3& mins = m_ndbvt.m_root->volume.Mins();
+//        const btVector3& maxs = m_ndbvt.m_root->volume.Maxs();
+//        const btScalar csm = getCollisionShape()->getMargin();
+//        const btVector3 mrg = btVector3(csm,
+//                                        csm,
+//                                        csm) *
+//                              1;  // ??? to investigate...
+//        m_bounds[0] = mins - mrg;
+//        m_bounds[1] = maxs + mrg;
+//        if (0 != getBroadphaseHandle())
+//        {
+//            m_worldInfo->m_broadphase->setAabb(getBroadphaseHandle(),
+//                                               m_bounds[0],
+//                                               m_bounds[1],
+//                                               m_worldInfo->m_dispatcher);
+//        }
+//    }
+//    else
+//    {
+//        m_bounds[0] =
+//            m_bounds[1] = btVector3(0, 0, 0);
+//    }
+    if (m_nodes.size())
     {
-		const btVector3& mins = m_ndbvt.m_root->volume.Mins();
+        btVector3 mins = m_nodes[0].m_x;
-		const btVector3& maxs = m_ndbvt.m_root->volume.Maxs();
+        btVector3 maxs = m_nodes[0].m_x;
+        for (int i = 1; i < m_nodes.size(); ++i)
+        {
+            for (int d = 0; d < 3; ++d)
+            {
+                if (m_nodes[i].m_x[d] > maxs[d])
+                    maxs[d] = m_nodes[i].m_x[d];
+                if (m_nodes[i].m_x[d] < mins[d])
+                    mins[d] = m_nodes[i].m_x[d];
+            }
+        }
         const btScalar csm = getCollisionShape()->getMargin();
         const btVector3 mrg = btVector3(csm,
                                         csm,
-										csm) *
+                                        csm);
-							  1;  // ??? to investigate...
         m_bounds[0] = mins - mrg;
         m_bounds[1] = maxs + mrg;
         if (0 != getBroadphaseHandle())
@@ -2452,7 +2485,6 @@ void btSoftBody::updateBounds()
         m_bounds[0] =
         m_bounds[1] = btVector3(0, 0, 0);
     }
-	//}
 }
 
 //