dali-physics/third-party/bullet3/src/BulletSoftBody/btDeformableMousePickingForce.h

   1 /*
   2  Written by Xuchen Han <xuchenhan2015@u.northwestern.edu>
   3
   4  Bullet Continuous Collision Detection and Physics Library
   5  Copyright (c) 2019 Google Inc. http://bulletphysics.org
   6  This software is provided 'as-is', without any express or implied warranty.
   7  In no event will the authors be held liable for any damages arising from the use of this software.
   8  Permission is granted to anyone to use this software for any purpose,
   9  including commercial applications, and to alter it and redistribute it freely,
  10  subject to the following restrictions:
  11  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.
  12  2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
  13  3. This notice may not be removed or altered from any source distribution.
  14  */
  15
  16 #ifndef BT_MOUSE_PICKING_FORCE_H
  17 #define BT_MOUSE_PICKING_FORCE_H
  18
  19 #include "btDeformableLagrangianForce.h"
  20
  21 class btDeformableMousePickingForce : public btDeformableLagrangianForce
  22 {
  23         // If true, the damping force will be in the direction of the spring
  24         // If false, the damping force will be in the direction of the velocity
  25         btScalar m_elasticStiffness, m_dampingStiffness;
  26         const btSoftBody::Face& m_face;
  27         btVector3 m_mouse_pos;
  28         btScalar m_maxForce;
  29
  30 public:
  31         typedef btAlignedObjectArray<btVector3> TVStack;
  32         btDeformableMousePickingForce(btScalar k, btScalar d, const btSoftBody::Face& face, const btVector3& mouse_pos, btScalar maxForce = 0.3) : m_elasticStiffness(k), m_dampingStiffness(d), m_face(face), m_mouse_pos(mouse_pos), m_maxForce(maxForce)
  33         {
  34         }
  35
  36         virtual void addScaledForces(btScalar scale, TVStack& force)
  37         {
  38                 addScaledDampingForce(scale, force);
  39                 addScaledElasticForce(scale, force);
  40         }
  41
  42         virtual void addScaledExplicitForce(btScalar scale, TVStack& force)
  43         {
  44                 addScaledElasticForce(scale, force);
  45         }
  46
  47         virtual void addScaledDampingForce(btScalar scale, TVStack& force)
  48         {
  49                 for (int i = 0; i < 3; ++i)
  50                 {
  51                         btVector3 v_diff = m_face.m_n[i]->m_v;
  52                         btVector3 scaled_force = scale * m_dampingStiffness * v_diff;
  53                         if ((m_face.m_n[i]->m_x - m_mouse_pos).norm() > SIMD_EPSILON)
  54                         {
  55                                 btVector3 dir = (m_face.m_n[i]->m_x - m_mouse_pos).normalized();
  56                                 scaled_force = scale * m_dampingStiffness * v_diff.dot(dir) * dir;
  57                         }
  58                         force[m_face.m_n[i]->index] -= scaled_force;
  59                 }
  60         }
  61
  62         virtual void addScaledElasticForce(btScalar scale, TVStack& force)
  63         {
  64                 btScalar scaled_stiffness = scale * m_elasticStiffness;
  65                 for (int i = 0; i < 3; ++i)
  66                 {
  67                         btVector3 dir = (m_face.m_n[i]->m_q - m_mouse_pos);
  68                         btVector3 scaled_force = scaled_stiffness * dir;
  69                         if (scaled_force.safeNorm() > m_maxForce)
  70                         {
  71                                 scaled_force.safeNormalize();
  72                                 scaled_force *= m_maxForce;
  73                         }
  74                         force[m_face.m_n[i]->index] -= scaled_force;
  75                 }
  76         }
  77
  78         virtual void addScaledDampingForceDifferential(btScalar scale, const TVStack& dv, TVStack& df)
  79         {
  80                 btScalar scaled_k_damp = m_dampingStiffness * scale;
  81                 for (int i = 0; i < 3; ++i)
  82                 {
  83                         btVector3 local_scaled_df = scaled_k_damp * dv[m_face.m_n[i]->index];
  84                         if ((m_face.m_n[i]->m_x - m_mouse_pos).norm() > SIMD_EPSILON)
  85                         {
  86                                 btVector3 dir = (m_face.m_n[i]->m_x - m_mouse_pos).normalized();
  87                                 local_scaled_df = scaled_k_damp * dv[m_face.m_n[i]->index].dot(dir) * dir;
  88                         }
  89                         df[m_face.m_n[i]->index] -= local_scaled_df;
  90                 }
  91         }
  92
  93         virtual void buildDampingForceDifferentialDiagonal(btScalar scale, TVStack& diagA) {}
  94
  95         virtual double totalElasticEnergy(btScalar dt)
  96         {
  97                 double energy = 0;
  98                 for (int i = 0; i < 3; ++i)
  99                 {
 100                         btVector3 dir = (m_face.m_n[i]->m_q - m_mouse_pos);
 101                         btVector3 scaled_force = m_elasticStiffness * dir;
 102                         if (scaled_force.safeNorm() > m_maxForce)
 103                         {
 104                                 scaled_force.safeNormalize();
 105                                 scaled_force *= m_maxForce;
 106                         }
 107                         energy += 0.5 * scaled_force.dot(dir);
 108                 }
 109                 return energy;
 110         }
 111
 112         virtual double totalDampingEnergy(btScalar dt)
 113         {
 114                 double energy = 0;
 115                 for (int i = 0; i < 3; ++i)
 116                 {
 117                         btVector3 v_diff = m_face.m_n[i]->m_v;
 118                         btVector3 scaled_force = m_dampingStiffness * v_diff;
 119                         if ((m_face.m_n[i]->m_x - m_mouse_pos).norm() > SIMD_EPSILON)
 120                         {
 121                                 btVector3 dir = (m_face.m_n[i]->m_x - m_mouse_pos).normalized();
 122                                 scaled_force = m_dampingStiffness * v_diff.dot(dir) * dir;
 123                         }
 124                         energy -= scaled_force.dot(m_face.m_n[i]->m_v) / dt;
 125                 }
 126                 return energy;
 127         }
 128
 129         virtual void addScaledElasticForceDifferential(btScalar scale, const TVStack& dx, TVStack& df)
 130         {
 131                 btScalar scaled_stiffness = scale * m_elasticStiffness;
 132                 for (int i = 0; i < 3; ++i)
 133                 {
 134                         btVector3 dir = (m_face.m_n[i]->m_q - m_mouse_pos);
 135                         btScalar dir_norm = dir.norm();
 136                         btVector3 dir_normalized = (dir_norm > SIMD_EPSILON) ? dir.normalized() : btVector3(0, 0, 0);
 137                         int id = m_face.m_n[i]->index;
 138                         btVector3 dx_diff = dx[id];
 139                         btScalar r = 0;  // rest length is 0 for picking spring
 140                         btVector3 scaled_df = btVector3(0, 0, 0);
 141                         if (dir_norm > SIMD_EPSILON)
 142                         {
 143                                 scaled_df -= scaled_stiffness * dir_normalized.dot(dx_diff) * dir_normalized;
 144                                 scaled_df += scaled_stiffness * dir_normalized.dot(dx_diff) * ((dir_norm - r) / dir_norm) * dir_normalized;
 145                                 scaled_df -= scaled_stiffness * ((dir_norm - r) / dir_norm) * dx_diff;
 146                         }
 147                         df[id] += scaled_df;
 148                 }
 149         }
 150
 151         void setMousePos(const btVector3& p)
 152         {
 153                 m_mouse_pos = p;
 154         }
 155
 156         virtual btDeformableLagrangianForceType getForceType()
 157         {
 158                 return BT_MOUSE_PICKING_FORCE;
 159         }
 160 };
 161
 162 #endif /* btMassSpring_h */