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diff --git a/thirdparty/bullet/BulletSoftBody/btDeformableContactConstraint.h b/thirdparty/bullet/BulletSoftBody/btDeformableContactConstraint.h
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+/*
+ Written by Xuchen Han <xuchenhan2015@u.northwestern.edu>
+ 
+ Bullet Continuous Collision Detection and Physics Library
+ Copyright (c) 2019 Google Inc. http://bulletphysics.org
+ 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.
+ */
+
+#ifndef BT_DEFORMABLE_CONTACT_CONSTRAINT_H
+#define BT_DEFORMABLE_CONTACT_CONSTRAINT_H
+#include "btSoftBody.h"
+
+// btDeformableContactConstraint is an abstract class specifying the method that each type of contact constraint needs to implement
+class btDeformableContactConstraint
+{
+public:
+    // True if the friction is static
+    // False if the friction is dynamic
+    bool m_static;
+    
+    // normal of the contact
+    btVector3 m_normal;
+    
+    btDeformableContactConstraint(const btVector3& normal): m_static(false), m_normal(normal)
+    {
+    }
+    
+    btDeformableContactConstraint(bool isStatic, const btVector3& normal): m_static(isStatic), m_normal(normal)
+    {
+    }
+    
+    btDeformableContactConstraint(const btDeformableContactConstraint& other)
+    : m_static(other.m_static)
+    , m_normal(other.m_normal)
+    {
+        
+    }
+    btDeformableContactConstraint(){}
+    
+    virtual ~btDeformableContactConstraint(){}
+    
+    // solve the constraint with inelastic impulse and return the error, which is the square of normal component of velocity diffrerence
+    // the constraint is solved by calculating the impulse between object A and B in the contact and apply the impulse to both objects involved in the contact
+    virtual btScalar solveConstraint() = 0;
+    
+    // solve the position error by applying an inelastic impulse that changes only the position (not velocity)
+    virtual btScalar solveSplitImpulse(const btContactSolverInfo& infoGlobal) = 0;
+    
+    // get the velocity of the object A in the contact
+    virtual btVector3 getVa() const = 0;
+    
+    // get the velocity of the object B in the contact
+    virtual btVector3 getVb() const = 0;
+    
+    // get the velocity change of the soft body node in the constraint
+    virtual btVector3 getDv(const btSoftBody::Node*) const = 0;
+    
+    // apply impulse to the soft body node and/or face involved
+    virtual void applyImpulse(const btVector3& impulse) = 0;
+    
+    // apply position based impulse to the soft body node and/or face involved
+    virtual void applySplitImpulse(const btVector3& impulse) = 0;
+    
+    // scale the penetration depth by erp
+    virtual void setPenetrationScale(btScalar scale) = 0;
+};
+
+//
+// Constraint that a certain node in the deformable objects cannot move
+class btDeformableStaticConstraint : public btDeformableContactConstraint
+{
+public:
+    const btSoftBody::Node* m_node;
+    
+    btDeformableStaticConstraint(){}
+    
+    btDeformableStaticConstraint(const btSoftBody::Node* node): m_node(node), btDeformableContactConstraint(false, btVector3(0,0,0))
+    {
+    }
+    
+    btDeformableStaticConstraint(const btDeformableStaticConstraint& other)
+    : m_node(other.m_node)
+    , btDeformableContactConstraint(other)
+    {
+        
+    }
+    
+    virtual ~btDeformableStaticConstraint(){}
+    
+    virtual btScalar solveConstraint()
+    {
+        return 0;
+    }
+    
+    virtual btScalar solveSplitImpulse(const btContactSolverInfo& infoGlobal)
+    {
+        return 0;
+    }
+
+    virtual btVector3 getVa() const
+    {
+        return btVector3(0,0,0);
+    }
+    
+    virtual btVector3 getVb() const
+    {
+        return btVector3(0,0,0);
+    }
+    
+    virtual btVector3 getDv(const btSoftBody::Node* n) const
+    {
+        return btVector3(0,0,0);
+    }
+    
+    virtual void applyImpulse(const btVector3& impulse){}
+    virtual void applySplitImpulse(const btVector3& impulse){}
+    virtual void setPenetrationScale(btScalar scale){}
+};
+
+//
+// Anchor Constraint between rigid and deformable node
+class btDeformableNodeAnchorConstraint : public btDeformableContactConstraint
+{
+public:
+    const btSoftBody::DeformableNodeRigidAnchor* m_anchor;
+    
+    btDeformableNodeAnchorConstraint(){}
+    btDeformableNodeAnchorConstraint(const btSoftBody::DeformableNodeRigidAnchor& c);
+    btDeformableNodeAnchorConstraint(const btDeformableNodeAnchorConstraint& other);
+    virtual ~btDeformableNodeAnchorConstraint()
+    {
+    }
+    virtual btScalar solveConstraint();
+    virtual btScalar solveSplitImpulse(const btContactSolverInfo& infoGlobal)
+    {
+        // todo xuchenhan@
+        return 0;
+    }
+    // object A is the rigid/multi body, and object B is the deformable node/face
+    virtual btVector3 getVa() const;
+    // get the velocity of the deformable node in contact
+    virtual btVector3 getVb() const;
+    virtual btVector3 getDv(const btSoftBody::Node* n) const
+    {
+        return btVector3(0,0,0);
+    }
+    virtual void applyImpulse(const btVector3& impulse);
+    virtual void applySplitImpulse(const btVector3& impulse)
+    {
+        // todo xuchenhan@
+    };
+    virtual void setPenetrationScale(btScalar scale){}
+};
+
+
+//
+// Constraint between rigid/multi body and deformable objects
+class btDeformableRigidContactConstraint : public btDeformableContactConstraint
+{
+public:
+    btVector3 m_total_normal_dv;
+    btVector3 m_total_tangent_dv;
+    btScalar m_penetration;
+    const btSoftBody::DeformableRigidContact* m_contact;
+    
+    btDeformableRigidContactConstraint(){}
+    btDeformableRigidContactConstraint(const btSoftBody::DeformableRigidContact& c);
+    btDeformableRigidContactConstraint(const btDeformableRigidContactConstraint& other);
+    virtual ~btDeformableRigidContactConstraint()
+    {
+    }
+    
+    // object A is the rigid/multi body, and object B is the deformable node/face
+    virtual btVector3 getVa() const;
+    
+    virtual btScalar solveConstraint();
+    
+    virtual btScalar solveSplitImpulse(const btContactSolverInfo& infoGlobal);
+    
+    virtual void setPenetrationScale(btScalar scale)
+    {
+        m_penetration *= scale;
+    }
+};
+
+//
+// Constraint between rigid/multi body and deformable objects nodes
+class btDeformableNodeRigidContactConstraint : public btDeformableRigidContactConstraint
+{
+public:
+    // the deformable node in contact
+    const btSoftBody::Node* m_node;
+    
+    btDeformableNodeRigidContactConstraint(){}
+    btDeformableNodeRigidContactConstraint(const btSoftBody::DeformableNodeRigidContact& contact);
+    btDeformableNodeRigidContactConstraint(const btDeformableNodeRigidContactConstraint& other);
+    
+    virtual ~btDeformableNodeRigidContactConstraint()
+    {
+    }
+    
+    // get the velocity of the deformable node in contact
+    virtual btVector3 getVb() const;
+    
+    // get the velocity change of the input soft body node in the constraint
+    virtual btVector3 getDv(const btSoftBody::Node*) const;
+    
+    // cast the contact to the desired type
+    const btSoftBody::DeformableNodeRigidContact* getContact() const
+    {
+        return static_cast<const btSoftBody::DeformableNodeRigidContact*>(m_contact);
+    }
+    
+    virtual void applyImpulse(const btVector3& impulse);
+    virtual void applySplitImpulse(const btVector3& impulse);
+};
+
+//
+// Constraint between rigid/multi body and deformable objects faces
+class btDeformableFaceRigidContactConstraint : public btDeformableRigidContactConstraint
+{
+public:
+    const btSoftBody::Face* m_face;
+    btDeformableFaceRigidContactConstraint(){}
+    btDeformableFaceRigidContactConstraint(const btSoftBody::DeformableFaceRigidContact& contact);
+    btDeformableFaceRigidContactConstraint(const btDeformableFaceRigidContactConstraint& other);
+    
+    virtual ~btDeformableFaceRigidContactConstraint()
+    {
+    }
+    
+    // get the velocity of the deformable face at the contact point
+    virtual btVector3 getVb() const;
+    
+    // get the velocity change of the input soft body node in the constraint
+    virtual btVector3 getDv(const btSoftBody::Node*) const;
+    
+    // cast the contact to the desired type
+    const btSoftBody::DeformableFaceRigidContact* getContact() const
+    {
+        return static_cast<const btSoftBody::DeformableFaceRigidContact*>(m_contact);
+    }
+    
+    virtual void applyImpulse(const btVector3& impulse);
+    virtual void applySplitImpulse(const btVector3& impulse);
+};
+
+//
+// Constraint between  deformable objects faces and deformable objects nodes
+class btDeformableFaceNodeContactConstraint : public btDeformableContactConstraint
+{
+public:
+    btSoftBody::Node* m_node;
+    btSoftBody::Face* m_face;
+    const btSoftBody::DeformableFaceNodeContact* m_contact;
+    btVector3 m_total_normal_dv;
+    btVector3 m_total_tangent_dv;
+    
+    btDeformableFaceNodeContactConstraint(){}
+    
+    btDeformableFaceNodeContactConstraint(const btSoftBody::DeformableFaceNodeContact& contact);
+    
+    virtual ~btDeformableFaceNodeContactConstraint(){}
+    
+    virtual btScalar solveConstraint();
+    
+    virtual btScalar solveSplitImpulse(const btContactSolverInfo& infoGlobal)
+    {
+        // todo: xuchenhan@
+        return 0;
+    }
+    
+    // get the velocity of the object A in the contact
+    virtual btVector3 getVa() const;
+    
+    // get the velocity of the object B in the contact
+    virtual btVector3 getVb() const;
+    
+    // get the velocity change of the input soft body node in the constraint
+    virtual btVector3 getDv(const btSoftBody::Node*) const;
+    
+    // cast the contact to the desired type
+    const btSoftBody::DeformableFaceNodeContact* getContact() const
+    {
+        return static_cast<const btSoftBody::DeformableFaceNodeContact*>(m_contact);
+    }
+    
+    virtual void applyImpulse(const btVector3& impulse);
+    virtual void applySplitImpulse(const btVector3& impulse)
+    {
+        // todo xuchenhan@
+    }
+    virtual void setPenetrationScale(btScalar scale){}
+};
+#endif /* BT_DEFORMABLE_CONTACT_CONSTRAINT_H */