btSoftBody.h

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/*
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.
*/
 
#ifndef _BT_SOFT_BODY_H
#define _BT_SOFT_BODY_H
 
#include "LinearMath/btAlignedObjectArray.h"
#include "LinearMath/btTransform.h"
#include "LinearMath/btIDebugDraw.h"
#include "LinearMath/btVector3.h"
#include "BulletDynamics/Dynamics/btRigidBody.h"
 
#include "BulletCollision/CollisionShapes/btConcaveShape.h"
#include "BulletCollision/CollisionDispatch/btCollisionCreateFunc.h"
#include "btSparseSDF.h"
#include "BulletCollision/BroadphaseCollision/btDbvt.h"
#include "BulletDynamics/Featherstone/btMultiBodyLinkCollider.h"
#include "BulletDynamics/Featherstone/btMultiBodyConstraint.h"
//#ifdef BT_USE_DOUBLE_PRECISION
//#define btRigidBodyData   btRigidBodyDoubleData
//#define btRigidBodyDataName   "btRigidBodyDoubleData"
//#else
#define btSoftBodyData btSoftBodyFloatData
#define btSoftBodyDataName "btSoftBodyFloatData"
static const btScalar OVERLAP_REDUCTION_FACTOR = 0.1;
static unsigned long seed = 243703;
//#endif //BT_USE_DOUBLE_PRECISION
 
class btBroadphaseInterface;
class btDispatcher;
class btSoftBodySolver;
 
/* btSoftBodyWorldInfo  */
struct btSoftBodyWorldInfo
{
    btScalar air_density;
    btScalar water_density;
    btScalar water_offset;
    btScalar m_maxDisplacement;
    btVector3 water_normal;
    btBroadphaseInterface* m_broadphase;
    btDispatcher* m_dispatcher;
    btVector3 m_gravity;
    btSparseSdf<3> m_sparsesdf;
 
    btSoftBodyWorldInfo()
        : air_density((btScalar)1.2),
          water_density(0),
          water_offset(0),
          m_maxDisplacement(1000.f),  //avoid soft body from 'exploding' so use some upper threshold of maximum motion that a node can travel per frame
          water_normal(0, 0, 0),
          m_broadphase(0),
          m_dispatcher(0),
          m_gravity(0, -10, 0)
    {
    }
};
 
class btSoftBody : public btCollisionObject
{
public:
    btAlignedObjectArray<const class btCollisionObject*> m_collisionDisabledObjects;
 
    // The solver object that handles this soft body
    btSoftBodySolver* m_softBodySolver;
 
    //
    // Enumerations
    //
 
    struct eAeroModel
    {
        enum _
        {
            V_Point,             
            V_TwoSided,          
            V_TwoSidedLiftDrag,  
            V_OneSided,          
            F_TwoSided,          
            F_TwoSidedLiftDrag,  
            F_OneSided,          
            END
        };
    };
 
    struct eVSolver
    {
        enum _
        {
            Linear,  
            END
        };
    };
 
    struct ePSolver
    {
        enum _
        {
            Linear,     
            Anchors,    
            RContacts,  
            SContacts,  
            END
        };
    };
 
    struct eSolverPresets
    {
        enum _
        {
            Positions,
            Velocities,
            Default = Positions,
            END
        };
    };
 
    struct eFeature
    {
        enum _
        {
            None,
            Node,
            Link,
            Face,
            Tetra,
            END
        };
    };
 
    typedef btAlignedObjectArray<eVSolver::_> tVSolverArray;
    typedef btAlignedObjectArray<ePSolver::_> tPSolverArray;
 
    //
    // Flags
    //
 
    struct fCollision
    {
        enum _
        {
            RVSmask = 0x000f,  
            SDF_RS = 0x0001,   
            CL_RS = 0x0002,    
            SDF_RD = 0x0004,   
 
            SVSmask = 0x00f0,  
            VF_SS = 0x0010,    
            CL_SS = 0x0020,    
            CL_SELF = 0x0040,  
            VF_DD = 0x0080,    
 
            RVDFmask = 0x0f00,  
            SDF_RDF = 0x0100,   
            SDF_MDF = 0x0200,   
            SDF_RDN = 0x0400,   
            /* presets  */
            Default = SDF_RS,
            END
        };
    };
 
    struct fMaterial
    {
        enum _
        {
            DebugDraw = 0x0001,  
            /* presets  */
            Default = DebugDraw,
            END
        };
    };
 
    //
    // API Types
    //
 
    /* sRayCast     */
    struct sRayCast
    {
        btSoftBody* body;     
        eFeature::_ feature;  
        int index;            
        btScalar fraction;    
    };
 
    /* ImplicitFn   */
    struct ImplicitFn
    {
        virtual ~ImplicitFn() {}
        virtual btScalar Eval(const btVector3& x) = 0;
    };
 
    //
    // Internal types
    //
 
    typedef btAlignedObjectArray<btScalar> tScalarArray;
    typedef btAlignedObjectArray<btVector3> tVector3Array;
 
    /* sCti is Softbody contact info    */
    struct sCti
    {
        const btCollisionObject* m_colObj; /* Rigid body            */
        btVector3 m_normal;                /* Outward normal        */
        btScalar m_offset;                 /* Offset from origin    */
        btVector3 m_bary;                  /* Barycentric weights for faces */
    };
 
    /* sMedium      */
    struct sMedium
    {
        btVector3 m_velocity; /* Velocity               */
        btScalar m_pressure;  /* Pressure               */
        btScalar m_density;   /* Density                */
    };
 
    /* Base type    */
    struct Element
    {
        void* m_tag;  // User data
        Element() : m_tag(0) {}
    };
    /* Material     */
    struct Material : Element
    {
        btScalar m_kLST;  // Linear stiffness coefficient [0,1]
        btScalar m_kAST;  // Area/Angular stiffness coefficient [0,1]
        btScalar m_kVST;  // Volume stiffness coefficient [0,1]
        int m_flags;      // Flags
    };
 
    /* Feature      */
    struct Feature : Element
    {
        Material* m_material;  // Material
    };
    /* Node         */
    struct Node : Feature
    {
        btVector3 m_x;       // Position
        btVector3 m_q;       // Previous step position/Test position
        btVector3 m_v;       // Velocity
        btVector3 m_vn;      // Previous step velocity
        btVector3 m_f;       // Force accumulator
        btVector3 m_n;       // Normal
        btScalar m_im;       // 1/mass
        btScalar m_area;     // Area
        btDbvtNode* m_leaf;  // Leaf data
        int m_constrained;   // depth of penetration
        int m_battach : 1;   // Attached
        int index;
        btVector3 m_splitv;               // velocity associated with split impulse
        btMatrix3x3 m_effectiveMass;      // effective mass in contact
        btMatrix3x3 m_effectiveMass_inv;  // inverse of effective mass
    };
    /* Link         */
    ATTRIBUTE_ALIGNED16(struct)
    Link : Feature
    {
        btVector3 m_c3;      // gradient
        Node* m_n[2];        // Node pointers
        btScalar m_rl;       // Rest length
        int m_bbending : 1;  // Bending link
        btScalar m_c0;       // (ima+imb)*kLST
        btScalar m_c1;       // rl^2
        btScalar m_c2;       // |gradient|^2/c0
 
        BT_DECLARE_ALIGNED_ALLOCATOR();
    };
    /* Face         */
    struct Face : Feature
    {
        Node* m_n[3];          // Node pointers
        btVector3 m_normal;    // Normal
        btScalar m_ra;         // Rest area
        btDbvtNode* m_leaf;    // Leaf data
        btVector4 m_pcontact;  // barycentric weights of the persistent contact
        btVector3 m_n0, m_n1, m_vn;
        int m_index;
    };
    /* Tetra        */
    struct Tetra : Feature
    {
        Node* m_n[4];              // Node pointers
        btScalar m_rv;             // Rest volume
        btDbvtNode* m_leaf;        // Leaf data
        btVector3 m_c0[4];         // gradients
        btScalar m_c1;             // (4*kVST)/(im0+im1+im2+im3)
        btScalar m_c2;             // m_c1/sum(|g0..3|^2)
        btMatrix3x3 m_Dm_inverse;  // rest Dm^-1
        btMatrix3x3 m_F;
        btScalar m_element_measure;
        btVector4 m_P_inv[3];  // first three columns of P_inv matrix
    };
 
    /*  TetraScratch  */
    struct TetraScratch
    {
        btMatrix3x3 m_F;           // deformation gradient F
        btScalar m_trace;          // trace of F^T * F
        btScalar m_J;              // det(F)
        btMatrix3x3 m_cofF;        // cofactor of F
        btMatrix3x3 m_corotation;  // corotatio of the tetra
    };
 
    /* RContact     */
    struct RContact
    {
        sCti m_cti;        // Contact infos
        Node* m_node;      // Owner node
        btMatrix3x3 m_c0;  // Impulse matrix
        btVector3 m_c1;    // Relative anchor
        btScalar m_c2;     // ima*dt
        btScalar m_c3;     // Friction
        btScalar m_c4;     // Hardness
 
        // jacobians and unit impulse responses for multibody
        btMultiBodyJacobianData jacobianData_normal;
        btMultiBodyJacobianData jacobianData_t1;
        btMultiBodyJacobianData jacobianData_t2;
        btVector3 t1;
        btVector3 t2;
    };
 
    class DeformableRigidContact
    {
    public:
        sCti m_cti;        // Contact infos
        btMatrix3x3 m_c0;  // Impulse matrix
        btVector3 m_c1;    // Relative anchor
        btScalar m_c2;     // inverse mass of node/face
        btScalar m_c3;     // Friction
        btScalar m_c4;     // Hardness
        btMatrix3x3 m_c5;  // inverse effective mass
 
        // jacobians and unit impulse responses for multibody
        btMultiBodyJacobianData jacobianData_normal;
        btMultiBodyJacobianData jacobianData_t1;
        btMultiBodyJacobianData jacobianData_t2;
        btVector3 t1;
        btVector3 t2;
    };
 
    class DeformableNodeRigidContact : public DeformableRigidContact
    {
    public:
        Node* m_node;  // Owner node
    };
 
    class DeformableNodeRigidAnchor : public DeformableNodeRigidContact
    {
    public:
        btVector3 m_local;  // Anchor position in body space
    };
 
    class DeformableFaceRigidContact : public DeformableRigidContact
    {
    public:
        Face* m_face;              // Owner face
        btVector3 m_contactPoint;  // Contact point
        btVector3 m_bary;          // Barycentric weights
        btVector3 m_weights;       // v_contactPoint * m_weights[i] = m_face->m_node[i]->m_v;
    };
 
    struct DeformableFaceNodeContact
    {
        Node* m_node;         // Node
        Face* m_face;         // Face
        btVector3 m_bary;     // Barycentric weights
        btVector3 m_weights;  // v_contactPoint * m_weights[i] = m_face->m_node[i]->m_v;
        btVector3 m_normal;   // Normal
        btScalar m_margin;    // Margin
        btScalar m_friction;  // Friction
        btScalar m_imf;       // inverse mass of the face at contact point
        btScalar m_c0;        // scale of the impulse matrix;
    };
 
    /* SContact     */
    struct SContact
    {
        Node* m_node;         // Node
        Face* m_face;         // Face
        btVector3 m_weights;  // Weigths
        btVector3 m_normal;   // Normal
        btScalar m_margin;    // Margin
        btScalar m_friction;  // Friction
        btScalar m_cfm[2];    // Constraint force mixing
    };
    /* Anchor       */
    struct Anchor
    {
        Node* m_node;         // Node pointer
        btVector3 m_local;    // Anchor position in body space
        btRigidBody* m_body;  // Body
        btScalar m_influence;
        btMatrix3x3 m_c0;  // Impulse matrix
        btVector3 m_c1;    // Relative anchor
        btScalar m_c2;     // ima*dt
    };
    /* Note         */
    struct Note : Element
    {
        const char* m_text;    // Text
        btVector3 m_offset;    // Offset
        int m_rank;            // Rank
        Node* m_nodes[4];      // Nodes
        btScalar m_coords[4];  // Coordinates
    };
    /* Pose         */
    struct Pose
    {
        bool m_bvolume;       // Is valid
        bool m_bframe;        // Is frame
        btScalar m_volume;    // Rest volume
        tVector3Array m_pos;  // Reference positions
        tScalarArray m_wgh;   // Weights
        btVector3 m_com;      // COM
        btMatrix3x3 m_rot;    // Rotation
        btMatrix3x3 m_scl;    // Scale
        btMatrix3x3 m_aqq;    // Base scaling
    };
    /* Cluster      */
    struct Cluster
    {
        tScalarArray m_masses;
        btAlignedObjectArray<Node*> m_nodes;
        tVector3Array m_framerefs;
        btTransform m_framexform;
        btScalar m_idmass;
        btScalar m_imass;
        btMatrix3x3 m_locii;
        btMatrix3x3 m_invwi;
        btVector3 m_com;
        btVector3 m_vimpulses[2];
        btVector3 m_dimpulses[2];
        int m_nvimpulses;
        int m_ndimpulses;
        btVector3 m_lv;
        btVector3 m_av;
        btDbvtNode* m_leaf;
        btScalar m_ndamping; /* Node damping        */
        btScalar m_ldamping; /* Linear damping  */
        btScalar m_adamping; /* Angular damping */
        btScalar m_matching;
        btScalar m_maxSelfCollisionImpulse;
        btScalar m_selfCollisionImpulseFactor;
        bool m_containsAnchor;
        bool m_collide;
        int m_clusterIndex;
        Cluster() : m_leaf(0), m_ndamping(0), m_ldamping(0), m_adamping(0), m_matching(0), m_maxSelfCollisionImpulse(100.f), m_selfCollisionImpulseFactor(0.01f), m_containsAnchor(false)
        {
        }
    };
    /* Impulse      */
    struct Impulse
    {
        btVector3 m_velocity;
        btVector3 m_drift;
        int m_asVelocity : 1;
        int m_asDrift : 1;
        Impulse() : m_velocity(0, 0, 0), m_drift(0, 0, 0), m_asVelocity(0), m_asDrift(0) {}
        Impulse operator-() const
        {
            Impulse i = *this;
            i.m_velocity = -i.m_velocity;
            i.m_drift = -i.m_drift;
            return (i);
        }
        Impulse operator*(btScalar x) const
        {
            Impulse i = *this;
            i.m_velocity *= x;
            i.m_drift *= x;
            return (i);
        }
    };
    /* Body         */
    struct Body
    {
        Cluster* m_soft;
        btRigidBody* m_rigid;
        const btCollisionObject* m_collisionObject;
 
        Body() : m_soft(0), m_rigid(0), m_collisionObject(0) {}
        Body(Cluster* p) : m_soft(p), m_rigid(0), m_collisionObject(0) {}
        Body(const btCollisionObject* colObj) : m_soft(0), m_collisionObject(colObj)
        {
            m_rigid = (btRigidBody*)btRigidBody::upcast(m_collisionObject);
        }
 
        void activate() const
        {
            if (m_rigid)
                m_rigid->activate();
            if (m_collisionObject)
                m_collisionObject->activate();
        }
        const btMatrix3x3& invWorldInertia() const
        {
            static const btMatrix3x3 iwi(0, 0, 0, 0, 0, 0, 0, 0, 0);
            if (m_rigid) return (m_rigid->getInvInertiaTensorWorld());
            if (m_soft) return (m_soft->m_invwi);
            return (iwi);
        }
        btScalar invMass() const
        {
            if (m_rigid) return (m_rigid->getInvMass());
            if (m_soft) return (m_soft->m_imass);
            return (0);
        }
        const btTransform& xform() const
        {
            static const btTransform identity = btTransform::getIdentity();
            if (m_collisionObject) return (m_collisionObject->getWorldTransform());
            if (m_soft) return (m_soft->m_framexform);
            return (identity);
        }
        btVector3 linearVelocity() const
        {
            if (m_rigid) return (m_rigid->getLinearVelocity());
            if (m_soft) return (m_soft->m_lv);
            return (btVector3(0, 0, 0));
        }
        btVector3 angularVelocity(const btVector3& rpos) const
        {
            if (m_rigid) return (btCross(m_rigid->getAngularVelocity(), rpos));
            if (m_soft) return (btCross(m_soft->m_av, rpos));
            return (btVector3(0, 0, 0));
        }
        btVector3 angularVelocity() const
        {
            if (m_rigid) return (m_rigid->getAngularVelocity());
            if (m_soft) return (m_soft->m_av);
            return (btVector3(0, 0, 0));
        }
        btVector3 velocity(const btVector3& rpos) const
        {
            return (linearVelocity() + angularVelocity(rpos));
        }
        void applyVImpulse(const btVector3& impulse, const btVector3& rpos) const
        {
            if (m_rigid) m_rigid->applyImpulse(impulse, rpos);
            if (m_soft) btSoftBody::clusterVImpulse(m_soft, rpos, impulse);
        }
        void applyDImpulse(const btVector3& impulse, const btVector3& rpos) const
        {
            if (m_rigid) m_rigid->applyImpulse(impulse, rpos);
            if (m_soft) btSoftBody::clusterDImpulse(m_soft, rpos, impulse);
        }
        void applyImpulse(const Impulse& impulse, const btVector3& rpos) const
        {
            if (impulse.m_asVelocity)
            {
                //              printf("impulse.m_velocity = %f,%f,%f\n",impulse.m_velocity.getX(),impulse.m_velocity.getY(),impulse.m_velocity.getZ());
                applyVImpulse(impulse.m_velocity, rpos);
            }
            if (impulse.m_asDrift)
            {
                //              printf("impulse.m_drift = %f,%f,%f\n",impulse.m_drift.getX(),impulse.m_drift.getY(),impulse.m_drift.getZ());
                applyDImpulse(impulse.m_drift, rpos);
            }
        }
        void applyVAImpulse(const btVector3& impulse) const
        {
            if (m_rigid) m_rigid->applyTorqueImpulse(impulse);
            if (m_soft) btSoftBody::clusterVAImpulse(m_soft, impulse);
        }
        void applyDAImpulse(const btVector3& impulse) const
        {
            if (m_rigid) m_rigid->applyTorqueImpulse(impulse);
            if (m_soft) btSoftBody::clusterDAImpulse(m_soft, impulse);
        }
        void applyAImpulse(const Impulse& impulse) const
        {
            if (impulse.m_asVelocity) applyVAImpulse(impulse.m_velocity);
            if (impulse.m_asDrift) applyDAImpulse(impulse.m_drift);
        }
        void applyDCImpulse(const btVector3& impulse) const
        {
            if (m_rigid) m_rigid->applyCentralImpulse(impulse);
            if (m_soft) btSoftBody::clusterDCImpulse(m_soft, impulse);
        }
    };
    /* Joint        */
    struct Joint
    {
        struct eType
        {
            enum _
            {
                Linear = 0,
                Angular,
                Contact
            };
        };
        struct Specs
        {
            Specs() : erp(1), cfm(1), split(1) {}
            btScalar erp;
            btScalar cfm;
            btScalar split;
        };
        Body m_bodies[2];
        btVector3 m_refs[2];
        btScalar m_cfm;
        btScalar m_erp;
        btScalar m_split;
        btVector3 m_drift;
        btVector3 m_sdrift;
        btMatrix3x3 m_massmatrix;
        bool m_delete;
        virtual ~Joint() {}
        Joint() : m_delete(false) {}
        virtual void Prepare(btScalar dt, int iterations);
        virtual void Solve(btScalar dt, btScalar sor) = 0;
        virtual void Terminate(btScalar dt) = 0;
        virtual eType::_ Type() const = 0;
    };
    /* LJoint       */
    struct LJoint : Joint
    {
        struct Specs : Joint::Specs
        {
            btVector3 position;
        };
        btVector3 m_rpos[2];
        void Prepare(btScalar dt, int iterations);
        void Solve(btScalar dt, btScalar sor);
        void Terminate(btScalar dt);
        eType::_ Type() const { return (eType::Linear); }
    };
    /* AJoint       */
    struct AJoint : Joint
    {
        struct IControl
        {
            virtual ~IControl() {}
            virtual void Prepare(AJoint*) {}
            virtual btScalar Speed(AJoint*, btScalar current) { return (current); }
            static IControl* Default()
            {
                static IControl def;
                return (&def);
            }
        };
        struct Specs : Joint::Specs
        {
            Specs() : icontrol(IControl::Default()) {}
            btVector3 axis;
            IControl* icontrol;
        };
        btVector3 m_axis[2];
        IControl* m_icontrol;
        void Prepare(btScalar dt, int iterations);
        void Solve(btScalar dt, btScalar sor);
        void Terminate(btScalar dt);
        eType::_ Type() const { return (eType::Angular); }
    };
    /* CJoint       */
    struct CJoint : Joint
    {
        int m_life;
        int m_maxlife;
        btVector3 m_rpos[2];
        btVector3 m_normal;
        btScalar m_friction;
        void Prepare(btScalar dt, int iterations);
        void Solve(btScalar dt, btScalar sor);
        void Terminate(btScalar dt);
        eType::_ Type() const { return (eType::Contact); }
    };
    /* Config       */
    struct Config
    {
        eAeroModel::_ aeromodel;    // Aerodynamic model (default: V_Point)
        btScalar kVCF;              // Velocities correction factor (Baumgarte)
        btScalar kDP;               // Damping coefficient [0,1]
        btScalar kDG;               // Drag coefficient [0,+inf]
        btScalar kLF;               // Lift coefficient [0,+inf]
        btScalar kPR;               // Pressure coefficient [-inf,+inf]
        btScalar kVC;               // Volume conversation coefficient [0,+inf]
        btScalar kDF;               // Dynamic friction coefficient [0,1]
        btScalar kMT;               // Pose matching coefficient [0,1]
        btScalar kCHR;              // Rigid contacts hardness [0,1]
        btScalar kKHR;              // Kinetic contacts hardness [0,1]
        btScalar kSHR;              // Soft contacts hardness [0,1]
        btScalar kAHR;              // Anchors hardness [0,1]
        btScalar kSRHR_CL;          // Soft vs rigid hardness [0,1] (cluster only)
        btScalar kSKHR_CL;          // Soft vs kinetic hardness [0,1] (cluster only)
        btScalar kSSHR_CL;          // Soft vs soft hardness [0,1] (cluster only)
        btScalar kSR_SPLT_CL;       // Soft vs rigid impulse split [0,1] (cluster only)
        btScalar kSK_SPLT_CL;       // Soft vs rigid impulse split [0,1] (cluster only)
        btScalar kSS_SPLT_CL;       // Soft vs rigid impulse split [0,1] (cluster only)
        btScalar maxvolume;         // Maximum volume ratio for pose
        btScalar timescale;         // Time scale
        int viterations;            // Velocities solver iterations
        int piterations;            // Positions solver iterations
        int diterations;            // Drift solver iterations
        int citerations;            // Cluster solver iterations
        int collisions;             // Collisions flags
        tVSolverArray m_vsequence;  // Velocity solvers sequence
        tPSolverArray m_psequence;  // Position solvers sequence
        tPSolverArray m_dsequence;  // Drift solvers sequence
        btScalar drag;              // deformable air drag
        btScalar m_maxStress;       // Maximum principle first Piola stress
    };
    /* SolverState  */
    struct SolverState
    {
        //if you add new variables, always initialize them!
        SolverState()
            : sdt(0),
              isdt(0),
              velmrg(0),
              radmrg(0),
              updmrg(0)
        {
        }
        btScalar sdt;     // dt*timescale
        btScalar isdt;    // 1/sdt
        btScalar velmrg;  // velocity margin
        btScalar radmrg;  // radial margin
        btScalar updmrg;  // Update margin
    };
    struct RayFromToCaster : btDbvt::ICollide
    {
        btVector3 m_rayFrom;
        btVector3 m_rayTo;
        btVector3 m_rayNormalizedDirection;
        btScalar m_mint;
        Face* m_face;
        int m_tests;
        RayFromToCaster(const btVector3& rayFrom, const btVector3& rayTo, btScalar mxt);
        void Process(const btDbvtNode* leaf);
 
        static /*inline*/ btScalar rayFromToTriangle(const btVector3& rayFrom,
                                                     const btVector3& rayTo,
                                                     const btVector3& rayNormalizedDirection,
                                                     const btVector3& a,
                                                     const btVector3& b,
                                                     const btVector3& c,
                                                     btScalar maxt = SIMD_INFINITY);
    };
 
    //
    // Typedefs
    //
 
    typedef void (*psolver_t)(btSoftBody*, btScalar, btScalar);
    typedef void (*vsolver_t)(btSoftBody*, btScalar);
    typedef btAlignedObjectArray<Cluster*> tClusterArray;
    typedef btAlignedObjectArray<Note> tNoteArray;
    typedef btAlignedObjectArray<Node> tNodeArray;
    typedef btAlignedObjectArray<btDbvtNode*> tLeafArray;
    typedef btAlignedObjectArray<Link> tLinkArray;
    typedef btAlignedObjectArray<Face> tFaceArray;
    typedef btAlignedObjectArray<Tetra> tTetraArray;
    typedef btAlignedObjectArray<Anchor> tAnchorArray;
    typedef btAlignedObjectArray<RContact> tRContactArray;
    typedef btAlignedObjectArray<SContact> tSContactArray;
    typedef btAlignedObjectArray<Material*> tMaterialArray;
    typedef btAlignedObjectArray<Joint*> tJointArray;
    typedef btAlignedObjectArray<btSoftBody*> tSoftBodyArray;
 
    //
    // Fields
    //
 
    Config m_cfg;                      // Configuration
    SolverState m_sst;                 // Solver state
    Pose m_pose;                       // Pose
    void* m_tag;                       // User data
    btSoftBodyWorldInfo* m_worldInfo;  // World info
    tNoteArray m_notes;                // Notes
    tNodeArray m_nodes;                // Nodes
    tNodeArray m_renderNodes;          // Nodes
    tLinkArray m_links;                // Links
    tFaceArray m_faces;                // Faces
    tFaceArray m_renderFaces;          // Faces
    tTetraArray m_tetras;              // Tetras
    btAlignedObjectArray<TetraScratch> m_tetraScratches;
    btAlignedObjectArray<TetraScratch> m_tetraScratchesTn;
    tAnchorArray m_anchors;  // Anchors
    btAlignedObjectArray<DeformableNodeRigidAnchor> m_deformableAnchors;
    tRContactArray m_rcontacts;  // Rigid contacts
    btAlignedObjectArray<DeformableNodeRigidContact> m_nodeRigidContacts;
    btAlignedObjectArray<DeformableFaceNodeContact> m_faceNodeContacts;
    btAlignedObjectArray<DeformableFaceRigidContact> m_faceRigidContacts;
    tSContactArray m_scontacts;     // Soft contacts
    tJointArray m_joints;           // Joints
    tMaterialArray m_materials;     // Materials
    btScalar m_timeacc;             // Time accumulator
    btVector3 m_bounds[2];          // Spatial bounds
    bool m_bUpdateRtCst;            // Update runtime constants
    btDbvt m_ndbvt;                 // Nodes tree
    btDbvt m_fdbvt;                 // Faces tree
    btDbvntNode* m_fdbvnt;          // Faces tree with normals
    btDbvt m_cdbvt;                 // Clusters tree
    tClusterArray m_clusters;       // Clusters
    btScalar m_dampingCoefficient;  // Damping Coefficient
    btScalar m_sleepingThreshold;
    btScalar m_maxSpeedSquared;
    btAlignedObjectArray<btVector3> m_quads;  // quadrature points for collision detection
    btScalar m_repulsionStiffness;
    btScalar m_gravityFactor;
    btAlignedObjectArray<btVector3> m_X;  // initial positions
 
    btAlignedObjectArray<btVector4> m_renderNodesInterpolationWeights;
    btAlignedObjectArray<btAlignedObjectArray<const btSoftBody::Node*> > m_renderNodesParents;
    btAlignedObjectArray<btScalar> m_z;  // vertical distance used in extrapolation
    bool m_useSelfCollision;
    bool m_softSoftCollision;
 
    btAlignedObjectArray<bool> m_clusterConnectivity;  //cluster connectivity, for self-collision
 
    btVector3 m_windVelocity;
 
    btScalar m_restLengthScale;
 
    //
    // Api
    //
 
    /* ctor                                                                 */
    btSoftBody(btSoftBodyWorldInfo* worldInfo, int node_count, const btVector3* x, const btScalar* m);
 
    /* ctor                                                                 */
    btSoftBody(btSoftBodyWorldInfo* worldInfo);
 
    void initDefaults();
 
    /* dtor                                                                 */
    virtual ~btSoftBody();
    /* Check for existing link                                              */
 
    btAlignedObjectArray<int> m_userIndexMapping;
 
    btSoftBodyWorldInfo* getWorldInfo()
    {
        return m_worldInfo;
    }
 
    void setDampingCoefficient(btScalar damping_coeff)
    {
        m_dampingCoefficient = damping_coeff;
    }
 
    virtual void setCollisionShape(btCollisionShape* collisionShape)
    {
    }
 
    bool checkLink(int node0,
                   int node1) const;
    bool checkLink(const Node* node0,
                   const Node* node1) const;
    /* Check for existring face                                             */
    bool checkFace(int node0,
                   int node1,
                   int node2) const;
    /* Append material                                                      */
    Material* appendMaterial();
    /* Append note                                                          */
    void appendNote(const char* text,
                    const btVector3& o,
                    const btVector4& c = btVector4(1, 0, 0, 0),
                    Node* n0 = 0,
                    Node* n1 = 0,
                    Node* n2 = 0,
                    Node* n3 = 0);
    void appendNote(const char* text,
                    const btVector3& o,
                    Node* feature);
    void appendNote(const char* text,
                    const btVector3& o,
                    Link* feature);
    void appendNote(const char* text,
                    const btVector3& o,
                    Face* feature);
    /* Append node                                                          */
    void appendNode(const btVector3& x, btScalar m);
    /* Append link                                                          */
    void appendLink(int model = -1, Material* mat = 0);
    void appendLink(int node0,
                    int node1,
                    Material* mat = 0,
                    bool bcheckexist = false);
    void appendLink(Node* node0,
                    Node* node1,
                    Material* mat = 0,
                    bool bcheckexist = false);
    /* Append face                                                          */
    void appendFace(int model = -1, Material* mat = 0);
    void appendFace(int node0,
                    int node1,
                    int node2,
                    Material* mat = 0);
    void appendTetra(int model, Material* mat);
    //
    void appendTetra(int node0,
                     int node1,
                     int node2,
                     int node3,
                     Material* mat = 0);
 
    /* Append anchor                                                        */
    void appendDeformableAnchor(int node, btRigidBody* body);
    void appendDeformableAnchor(int node, btMultiBodyLinkCollider* link);
    void appendAnchor(int node,
                      btRigidBody* body, bool disableCollisionBetweenLinkedBodies = false, btScalar influence = 1);
    void appendAnchor(int node, btRigidBody* body, const btVector3& localPivot, bool disableCollisionBetweenLinkedBodies = false, btScalar influence = 1);
    void removeAnchor(int node);
    /* Append linear joint                                                  */
    void appendLinearJoint(const LJoint::Specs& specs, Cluster* body0, Body body1);
    void appendLinearJoint(const LJoint::Specs& specs, Body body = Body());
    void appendLinearJoint(const LJoint::Specs& specs, btSoftBody* body);
    /* Append linear joint                                                  */
    void appendAngularJoint(const AJoint::Specs& specs, Cluster* body0, Body body1);
    void appendAngularJoint(const AJoint::Specs& specs, Body body = Body());
    void appendAngularJoint(const AJoint::Specs& specs, btSoftBody* body);
    /* Add force (or gravity) to the entire body                            */
    void addForce(const btVector3& force);
    /* Add force (or gravity) to a node of the body                         */
    void addForce(const btVector3& force,
                  int node);
    /* Add aero force to a node of the body */
    void addAeroForceToNode(const btVector3& windVelocity, int nodeIndex);
 
    /* Add aero force to a face of the body */
    void addAeroForceToFace(const btVector3& windVelocity, int faceIndex);
 
    /* Add velocity to the entire body                                      */
    void addVelocity(const btVector3& velocity);
 
    /* Set velocity for the entire body                                     */
    void setVelocity(const btVector3& velocity);
 
    /* Add velocity to a node of the body                                   */
    void addVelocity(const btVector3& velocity,
                     int node);
    /* Set mass                                                             */
    void setMass(int node,
                 btScalar mass);
    /* Get mass                                                             */
    btScalar getMass(int node) const;
    /* Get total mass                                                       */
    btScalar getTotalMass() const;
    /* Set total mass (weighted by previous masses)                         */
    void setTotalMass(btScalar mass,
                      bool fromfaces = false);
    /* Set total density                                                    */
    void setTotalDensity(btScalar density);
    /* Set volume mass (using tetrahedrons)                                 */
    void setVolumeMass(btScalar mass);
    /* Set volume density (using tetrahedrons)                              */
    void setVolumeDensity(btScalar density);
    /* Get the linear velocity of the center of mass                        */
    btVector3 getLinearVelocity();
    /* Set the linear velocity of the center of mass                        */
    void setLinearVelocity(const btVector3& linVel);
    /* Set the angular velocity of the center of mass                       */
    void setAngularVelocity(const btVector3& angVel);
    /* Get best fit rigid transform                                         */
    btTransform getRigidTransform();
    /* Transform to given pose                                              */
    void transformTo(const btTransform& trs);
    /* Transform                                                            */
    void transform(const btTransform& trs);
    /* Translate                                                            */
    void translate(const btVector3& trs);
    /* Rotate                                                           */
    void rotate(const btQuaternion& rot);
    /* Scale                                                                */
    void scale(const btVector3& scl);
    /* Get link resting lengths scale                                       */
    btScalar getRestLengthScale();
    /* Scale resting length of all springs                                  */
    void setRestLengthScale(btScalar restLength);
    /* Set current state as pose                                            */
    void setPose(bool bvolume,
                 bool bframe);
    /* Set current link lengths as resting lengths                          */
    void resetLinkRestLengths();
    /* Return the volume                                                    */
    btScalar getVolume() const;
    /* Cluster count                                                        */
    btVector3 getCenterOfMass() const
    {
        btVector3 com(0, 0, 0);
        for (int i = 0; i < m_nodes.size(); i++)
        {
            com += (m_nodes[i].m_x * this->getMass(i));
        }
        com /= this->getTotalMass();
        return com;
    }
    int clusterCount() const;
    /* Cluster center of mass                                               */
    static btVector3 clusterCom(const Cluster* cluster);
    btVector3 clusterCom(int cluster) const;
    /* Cluster velocity at rpos                                             */
    static btVector3 clusterVelocity(const Cluster* cluster, const btVector3& rpos);
    /* Cluster impulse                                                      */
    static void clusterVImpulse(Cluster* cluster, const btVector3& rpos, const btVector3& impulse);
    static void clusterDImpulse(Cluster* cluster, const btVector3& rpos, const btVector3& impulse);
    static void clusterImpulse(Cluster* cluster, const btVector3& rpos, const Impulse& impulse);
    static void clusterVAImpulse(Cluster* cluster, const btVector3& impulse);
    static void clusterDAImpulse(Cluster* cluster, const btVector3& impulse);
    static void clusterAImpulse(Cluster* cluster, const Impulse& impulse);
    static void clusterDCImpulse(Cluster* cluster, const btVector3& impulse);
    /* Generate bending constraints based on distance in the adjency graph  */
    int generateBendingConstraints(int distance,
                                   Material* mat = 0);
    /* Randomize constraints to reduce solver bias                          */
    void randomizeConstraints();
    /* Release clusters                                                     */
    void releaseCluster(int index);
    void releaseClusters();
    /* Generate clusters (K-mean)                                           */
    int generateClusters(int k, int maxiterations = 8192);
    /* Refine                                                               */
    void refine(ImplicitFn* ifn, btScalar accurary, bool cut);
    /* CutLink                                                              */
    bool cutLink(int node0, int node1, btScalar position);
    bool cutLink(const Node* node0, const Node* node1, btScalar position);
 
    bool rayTest(const btVector3& rayFrom,
                 const btVector3& rayTo,
                 sRayCast& results);
    bool rayFaceTest(const btVector3& rayFrom,
                     const btVector3& rayTo,
                     sRayCast& results);
    int rayFaceTest(const btVector3& rayFrom, const btVector3& rayTo,
                    btScalar& mint, int& index) const;
    /* Solver presets                                                       */
    void setSolver(eSolverPresets::_ preset);
    /* predictMotion                                                        */
    void predictMotion(btScalar dt);
    /* solveConstraints                                                     */
    void solveConstraints();
    /* staticSolve                                                          */
    void staticSolve(int iterations);
    /* solveCommonConstraints                                               */
    static void solveCommonConstraints(btSoftBody** bodies, int count, int iterations);
    /* solveClusters                                                        */
    static void solveClusters(const btAlignedObjectArray<btSoftBody*>& bodies);
    /* integrateMotion                                                      */
    void integrateMotion();
    /* defaultCollisionHandlers                                             */
    void defaultCollisionHandler(const btCollisionObjectWrapper* pcoWrap);
    void defaultCollisionHandler(btSoftBody* psb);
    void setSelfCollision(bool useSelfCollision);
    bool useSelfCollision();
    void updateDeactivation(btScalar timeStep);
    void setZeroVelocity();
    bool wantsSleeping();
 
    //
    // Functionality to deal with new accelerated solvers.
    //
 
    void setWindVelocity(const btVector3& velocity);
 
    const btVector3& getWindVelocity();
 
    //
    // Set the solver that handles this soft body
    // Should not be allowed to get out of sync with reality
    // Currently called internally on addition to the world
    void setSoftBodySolver(btSoftBodySolver* softBodySolver)
    {
        m_softBodySolver = softBodySolver;
    }
 
    //
    // Return the solver that handles this soft body
    //
    btSoftBodySolver* getSoftBodySolver()
    {
        return m_softBodySolver;
    }
 
    //
    // Return the solver that handles this soft body
    //
    btSoftBodySolver* getSoftBodySolver() const
    {
        return m_softBodySolver;
    }
 
    //
    // Cast
    //
 
    static const btSoftBody* upcast(const btCollisionObject* colObj)
    {
        if (colObj->getInternalType() == CO_SOFT_BODY)
            return (const btSoftBody*)colObj;
        return 0;
    }
    static btSoftBody* upcast(btCollisionObject* colObj)
    {
        if (colObj->getInternalType() == CO_SOFT_BODY)
            return (btSoftBody*)colObj;
        return 0;
    }
 
    //
    // ::btCollisionObject
    //
 
    virtual void getAabb(btVector3& aabbMin, btVector3& aabbMax) const
    {
        aabbMin = m_bounds[0];
        aabbMax = m_bounds[1];
    }
    //
    // Private
    //
    void pointersToIndices();
    void indicesToPointers(const int* map = 0);
 
    int rayTest(const btVector3& rayFrom, const btVector3& rayTo,
                btScalar& mint, eFeature::_& feature, int& index, bool bcountonly) const;
    void initializeFaceTree();
    void rebuildNodeTree();
    btVector3 evaluateCom() const;
    bool checkDeformableContact(const btCollisionObjectWrapper* colObjWrap, const btVector3& x, btScalar margin, btSoftBody::sCti& cti, bool predict = false) const;
    bool checkDeformableFaceContact(const btCollisionObjectWrapper* colObjWrap, Face& f, btVector3& contact_point, btVector3& bary, btScalar margin, btSoftBody::sCti& cti, bool predict = false) const;
    bool checkContact(const btCollisionObjectWrapper* colObjWrap, const btVector3& x, btScalar margin, btSoftBody::sCti& cti) const;
    void updateNormals();
    void updateBounds();
    void updatePose();
    void updateConstants();
    void updateLinkConstants();
    void updateArea(bool averageArea = true);
    void initializeClusters();
    void updateClusters();
    void cleanupClusters();
    void prepareClusters(int iterations);
    void solveClusters(btScalar sor);
    void applyClusters(bool drift);
    void dampClusters();
    void setSpringStiffness(btScalar k);
    void setGravityFactor(btScalar gravFactor);
    void initializeDmInverse();
    void updateDeformation();
    void advanceDeformation();
    void applyForces();
    void setMaxStress(btScalar maxStress);
    void interpolateRenderMesh();
    void setCollisionQuadrature(int N);
    static void PSolve_Anchors(btSoftBody* psb, btScalar kst, btScalar ti);
    static void PSolve_RContacts(btSoftBody* psb, btScalar kst, btScalar ti);
    static void PSolve_SContacts(btSoftBody* psb, btScalar, btScalar ti);
    static void PSolve_Links(btSoftBody* psb, btScalar kst, btScalar ti);
    static void VSolve_Links(btSoftBody* psb, btScalar kst);
    static psolver_t getSolver(ePSolver::_ solver);
    static vsolver_t getSolver(eVSolver::_ solver);
    void geometricCollisionHandler(btSoftBody* psb);
#define SAFE_EPSILON SIMD_EPSILON * 100.0
    void updateNode(btDbvtNode* node, bool use_velocity, bool margin)
    {
        if (node->isleaf())
        {
            btSoftBody::Node* n = (btSoftBody::Node*)(node->data);
            ATTRIBUTE_ALIGNED16(btDbvtVolume)
            vol;
            btScalar pad = margin ? m_sst.radmrg : SAFE_EPSILON;  // use user defined margin or margin for floating point precision
            if (use_velocity)
            {
                btVector3 points[2] = {n->m_x, n->m_x + m_sst.sdt * n->m_v};
                vol = btDbvtVolume::FromPoints(points, 2);
                vol.Expand(btVector3(pad, pad, pad));
            }
            else
            {
                vol = btDbvtVolume::FromCR(n->m_x, pad);
            }
            node->volume = vol;
            return;
        }
        else
        {
            updateNode(node->childs[0], use_velocity, margin);
            updateNode(node->childs[1], use_velocity, margin);
            ATTRIBUTE_ALIGNED16(btDbvtVolume)
            vol;
            Merge(node->childs[0]->volume, node->childs[1]->volume, vol);
            node->volume = vol;
        }
    }
 
    void updateNodeTree(bool use_velocity, bool margin)
    {
        if (m_ndbvt.m_root)
            updateNode(m_ndbvt.m_root, use_velocity, margin);
    }
 
    template <class DBVTNODE>  // btDbvtNode or btDbvntNode
    void updateFace(DBVTNODE* node, bool use_velocity, bool margin)
    {
        if (node->isleaf())
        {
            btSoftBody::Face* f = (btSoftBody::Face*)(node->data);
            btScalar pad = margin ? m_sst.radmrg : SAFE_EPSILON;  // use user defined margin or margin for floating point precision
            ATTRIBUTE_ALIGNED16(btDbvtVolume)
            vol;
            if (use_velocity)
            {
                btVector3 points[6] = {f->m_n[0]->m_x, f->m_n[0]->m_x + m_sst.sdt * f->m_n[0]->m_v,
                                       f->m_n[1]->m_x, f->m_n[1]->m_x + m_sst.sdt * f->m_n[1]->m_v,
                                       f->m_n[2]->m_x, f->m_n[2]->m_x + m_sst.sdt * f->m_n[2]->m_v};
                vol = btDbvtVolume::FromPoints(points, 6);
            }
            else
            {
                btVector3 points[3] = {f->m_n[0]->m_x,
                                       f->m_n[1]->m_x,
                                       f->m_n[2]->m_x};
                vol = btDbvtVolume::FromPoints(points, 3);
            }
            vol.Expand(btVector3(pad, pad, pad));
            node->volume = vol;
            return;
        }
        else
        {
            updateFace(node->childs[0], use_velocity, margin);
            updateFace(node->childs[1], use_velocity, margin);
            ATTRIBUTE_ALIGNED16(btDbvtVolume)
            vol;
            Merge(node->childs[0]->volume, node->childs[1]->volume, vol);
            node->volume = vol;
        }
    }
    void updateFaceTree(bool use_velocity, bool margin)
    {
        if (m_fdbvt.m_root)
            updateFace(m_fdbvt.m_root, use_velocity, margin);
        if (m_fdbvnt)
            updateFace(m_fdbvnt, use_velocity, margin);
    }
 
    template <typename T>
    static inline T BaryEval(const T& a,
                             const T& b,
                             const T& c,
                             const btVector3& coord)
    {
        return (a * coord.x() + b * coord.y() + c * coord.z());
    }
 
    void applyRepulsionForce(btScalar timeStep, bool applySpringForce)
    {
        btAlignedObjectArray<int> indices;
        {
            // randomize the order of repulsive force
            indices.resize(m_faceNodeContacts.size());
            for (int i = 0; i < m_faceNodeContacts.size(); ++i)
                indices[i] = i;
#define NEXTRAND (seed = (1664525L * seed + 1013904223L) & 0xffffffff)
            int i, ni;
 
            for (i = 0, ni = indices.size(); i < ni; ++i)
            {
                btSwap(indices[i], indices[NEXTRAND % ni]);
            }
        }
        for (int k = 0; k < m_faceNodeContacts.size(); ++k)
        {
            int i = indices[k];
            btSoftBody::DeformableFaceNodeContact& c = m_faceNodeContacts[i];
            btSoftBody::Node* node = c.m_node;
            btSoftBody::Face* face = c.m_face;
            const btVector3& w = c.m_bary;
            const btVector3& n = c.m_normal;
            btVector3 l = node->m_x - BaryEval(face->m_n[0]->m_x, face->m_n[1]->m_x, face->m_n[2]->m_x, w);
            btScalar d = c.m_margin - n.dot(l);
            d = btMax(btScalar(0), d);
 
            const btVector3& va = node->m_v;
            btVector3 vb = BaryEval(face->m_n[0]->m_v, face->m_n[1]->m_v, face->m_n[2]->m_v, w);
            btVector3 vr = va - vb;
            const btScalar vn = btDot(vr, n);  // dn < 0 <==> opposing
            if (vn > OVERLAP_REDUCTION_FACTOR * d / timeStep)
                continue;
            btVector3 vt = vr - vn * n;
            btScalar I = 0;
            btScalar mass = node->m_im == 0 ? 0 : btScalar(1) / node->m_im;
            if (applySpringForce)
                I = -btMin(m_repulsionStiffness * timeStep * d, mass * (OVERLAP_REDUCTION_FACTOR * d / timeStep - vn));
            if (vn < 0)
                I += 0.5 * mass * vn;
            int face_penetration = 0, node_penetration = node->m_constrained;
            for (int i = 0; i < 3; ++i)
                face_penetration |= face->m_n[i]->m_constrained;
            btScalar I_tilde = 2.0 * I / (1.0 + w.length2());
 
            //             double the impulse if node or face is constrained.
            if (face_penetration > 0 || node_penetration > 0)
            {
                I_tilde *= 2.0;
            }
            if (face_penetration <= 0)
            {
                for (int j = 0; j < 3; ++j)
                    face->m_n[j]->m_v += w[j] * n * I_tilde * node->m_im;
            }
            if (node_penetration <= 0)
            {
                node->m_v -= I_tilde * node->m_im * n;
            }
 
            // apply frictional impulse
            btScalar vt_norm = vt.safeNorm();
            if (vt_norm > SIMD_EPSILON)
            {
                btScalar delta_vn = -2 * I * node->m_im;
                btScalar mu = c.m_friction;
                btScalar vt_new = btMax(btScalar(1) - mu * delta_vn / (vt_norm + SIMD_EPSILON), btScalar(0)) * vt_norm;
                I = 0.5 * mass * (vt_norm - vt_new);
                vt.safeNormalize();
                I_tilde = 2.0 * I / (1.0 + w.length2());
                //                 double the impulse if node or face is constrained.
                if (face_penetration > 0 || node_penetration > 0)
                    I_tilde *= 2.0;
                if (face_penetration <= 0)
                {
                    for (int j = 0; j < 3; ++j)
                        face->m_n[j]->m_v += w[j] * vt * I_tilde * (face->m_n[j])->m_im;
                }
                if (node_penetration <= 0)
                {
                    node->m_v -= I_tilde * node->m_im * vt;
                }
            }
        }
    }
    virtual int calculateSerializeBufferSize() const;
 
    virtual const char* serialize(void* dataBuffer, class btSerializer* serializer) const;
};
 
#endif  //_BT_SOFT_BODY_H