Demos/FractureDemo/btFractureBody.cpp

   1 \r
   2 #include "btFractureBody.h"\r
   3 #include "BulletCollision/CollisionDispatch/btCollisionWorld.h"\r
   4 #include "BulletCollision/CollisionShapes/btCompoundShape.h"\r
   5 #include "BulletDynamics/Dynamics/btDynamicsWorld.h"\r
   6 \r
   7 \r
   8 \r
   9 void    btFractureBody::recomputeConnectivity(btCollisionWorld* world)\r
  10 {\r
  11         m_connections.clear();\r
  12         //@todo use the AABB tree to avoid N^2 checks\r
  13 \r
  14         if (getCollisionShape()->isCompound())\r
  15         {\r
  16                 btCompoundShape* compound = (btCompoundShape*)getCollisionShape();\r
  17                 for (int i=0;i<compound->getNumChildShapes();i++)\r
  18                 {\r
  19                         for (int j=i+1;j<compound->getNumChildShapes();j++)\r
  20                         {\r
  21 \r
  22                                 struct   MyContactResultCallback : public btCollisionWorld::ContactResultCallback\r
  23                                 {\r
  24                                         bool m_connected;\r
  25                                         MyContactResultCallback() :m_connected(false)\r
  26                                         {\r
  27                                         }\r
  28                                         virtual   btScalar   addSingleResult(btManifoldPoint& cp,   const btCollisionObject* colObj0,int partId0,int index0,const btCollisionObject* colObj1,int partId1,int index1)\r
  29                                         {\r
  30                                                 if (cp.getDistance()<=0)\r
  31                                                         m_connected = true;\r
  32                                                 return 1.f;\r
  33                                         }\r
  34                            };\r
  35 \r
  36                                 MyContactResultCallback result;\r
  37 \r
  38                                 btCollisionObject obA;\r
  39                                 obA.setWorldTransform(compound->getChildTransform(i));\r
  40                                 obA.setCollisionShape(compound->getChildShape(i));\r
  41                                 btCollisionObject obB;\r
  42                                 obB.setWorldTransform(compound->getChildTransform(j));\r
  43                                 obB.setCollisionShape(compound->getChildShape(j));\r
  44                                 world->contactPairTest(&obA,&obB,result);\r
  45                                 if (result.m_connected)\r
  46                                 {\r
  47                                         btConnection tmp;\r
  48                                         tmp.m_childIndex0 = i;\r
  49                                         tmp.m_childIndex1 = j;\r
  50                                         tmp.m_childShape0 = compound->getChildShape(i);\r
  51                                         tmp.m_childShape1 = compound->getChildShape(j);\r
  52                                         tmp.m_strength = 1.f;//??\r
  53                                         m_connections.push_back(tmp);\r
  54                                 }\r
  55                         }\r
  56                 }\r
  57         }\r
  58         \r
  59 \r
  60 }\r
  61 \r
  62 btCompoundShape* btFractureBody::shiftTransformDistributeMass(btCompoundShape* boxCompound,btScalar mass,btTransform& shift)\r
  63 {\r
  64 \r
  65         btVector3 principalInertia;\r
  66 \r
  67         btScalar* masses = new btScalar[boxCompound->getNumChildShapes()];\r
  68         for (int j=0;j<boxCompound->getNumChildShapes();j++)\r
  69         {\r
  70                 //evenly distribute mass\r
  71                 masses[j]=mass/boxCompound->getNumChildShapes();\r
  72         }\r
  73 \r
  74         return shiftTransform(boxCompound,masses,shift,principalInertia);\r
  75 \r
  76 }\r
  77 \r
  78 \r
  79 btCompoundShape* btFractureBody::shiftTransform(btCompoundShape* boxCompound,btScalar* masses,btTransform& shift, btVector3& principalInertia)\r
  80 {\r
  81         btTransform principal;\r
  82 \r
  83         boxCompound->calculatePrincipalAxisTransform(masses,principal,principalInertia);\r
  84 \r
  85 \r
  86         ///create a new compound with world transform/center of mass properly aligned with the principal axis\r
  87 \r
  88         ///non-recursive compound shapes perform better\r
  89         \r
  90 #ifdef USE_RECURSIVE_COMPOUND\r
  91 \r
  92         btCompoundShape* newCompound = new btCompoundShape();\r
  93         newCompound->addChildShape(principal.inverse(),boxCompound);\r
  94         newBoxCompound = newCompound;\r
  95         //m_collisionShapes.push_back(newCompound);\r
  96 \r
  97         //btDefaultMotionState* myMotionState = new btDefaultMotionState(startTransform);\r
  98         //btRigidBody::btRigidBodyConstructionInfo rbInfo(mass,myMotionState,newCompound,principalInertia);\r
  99 \r
 100 #else\r
 101 #ifdef CHANGE_COMPOUND_INPLACE\r
 102         newBoxCompound = boxCompound;\r
 103         for (int i=0;i<boxCompound->getNumChildShapes();i++)\r
 104         {\r
 105                 btTransform newChildTransform = principal.inverse()*boxCompound->getChildTransform(i);\r
 106                 ///updateChildTransform is really slow, because it re-calculates the AABB each time. todo: add option to disable this update\r
 107                 boxCompound->updateChildTransform(i,newChildTransform);\r
 108         }\r
 109         bool isDynamic = (mass != 0.f);\r
 110         btVector3 localInertia(0,0,0);\r
 111         if (isDynamic)\r
 112                 boxCompound->calculateLocalInertia(mass,localInertia);\r
 113         \r
 114 #else\r
 115         ///creation is faster using a new compound to store the shifted children\r
 116         btCompoundShape* newBoxCompound = new btCompoundShape();\r
 117         for (int i=0;i<boxCompound->getNumChildShapes();i++)\r
 118         {\r
 119                 btTransform newChildTransform = principal.inverse()*boxCompound->getChildTransform(i);\r
 120                 ///updateChildTransform is really slow, because it re-calculates the AABB each time. todo: add option to disable this update\r
 121                 newBoxCompound->addChildShape(newChildTransform,boxCompound->getChildShape(i));\r
 122         }\r
 123 \r
 124 \r
 125 \r
 126 #endif\r
 127 \r
 128 #endif//USE_RECURSIVE_COMPOUND\r
 129 \r
 130         shift = principal;\r
 131         return newBoxCompound;\r
 132 }\r
 133 \r
 134 \r
 135 \r
 136 \r
 137 \r
 138 \r