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Bullet 刚体与软体的碰撞 collisions between rigidbody and softbody in Bullet
上一篇文章做了一个bullet刚体自由落体的模拟，这篇文章模拟软体与刚体的碰撞，并且让软体保持碰撞后的形状。关于软体的参数配置如下：
btSoftBody::Config :
btSoftBody::Config::aeromodel; // Aerodynamic model (default: V_Point)
define what kind feature is used to compute aerodynamic forces.
btSoftBody::Config::kVCF; // Velocities correction factor (Baumgarte)
define the amount of correction per time step for drift solver (sometimes referred as ERP in rigid bodies solvers).
btSoftBody::Config::kDP; // Damping coefficient [0,1]
damping, zero = no damping, one= full damping.
btSoftBody::Config::kDG; // Drag coefficient [0,+inf]
[aerodynamic]=> is referred in http://en.wikipedia.org/wiki/Drag_%28force%29 as ‘Cd‘, kDG=0 mean no drag.
btSoftBody::Config::kLF; // Lift coefficient [0,+inf]
[aerodynamic]=> is a factor of the lift force (http://en.wikipedia.org/wiki/Lift_%28force%29) kLF=0 mean no lift
btSoftBody::Config::kPR; // Pressure coefficient [-inf,+inf]
[aerodynamic]=> is a factor of pressure.
btSoftBody::Config::kVC; // Volume conversation coefficient [0,+inf]
when ‘setPose(true,...)‘ as been called, define the magnitude of the force used to conserve volume.
btSoftBody::Config::kDF; // Dynamic friction coefficient [0,1]
friction, kDF=0 mean sliding, kDF=1 mean sticking.
btSoftBody::Config::kMT; // Pose matching coefficient [0,1]
when ‘setPose(...,true)‘ as been called, define the factor used for pose matching.
btSoftBody::Config::kCHR; // Rigid contacts hardness [0,1]
define how ‘soft‘ contact with rigid bodies are, kCHR=0 mean no penetration correction, 1 mean full correction.
btSoftBody::Config::kKHR; // Kinetic contacts hardness [0,1]
define how ‘soft‘ contact with kinetic/static bodies are, kKHR=0 mean no penetration correction, 1 mean full correction.
btSoftBody::Config::kSHR; // Soft contacts hardness [0,1]
define how ‘soft‘ contact with other soft bodies are, kSHR=0 mean no penetration correction, 1 mean full correction.
btSoftBody::Config::kAHR; // Anchors hardness [0,1]
define how ‘soft‘ anchor constraint (joint) are, kAHR=0 mean no drift correction, 1 mean full correction.
btSoftBody::Config::maxvolume; // Maximum volume ratio for pose
--unused--
btSoftBody::Config::timescale; // Time scale
factor of time step, can be used to speed up, or slow down simulation, default=1.
btSoftBody::Config::viterations; // Velocities solver iterations
number of iterations for velocity solvers (if any).
btSoftBody::Config::piterations; // Positions solver iterations
number of iterations for position solvers (if any).
btSoftBody::Config::diterations; // Drift solver iterations
number of iterations for drift solvers (if any).
btSoftBody::Config::collisions; // Collisions flags
see btSoftBody::fCollision.
btSoftBody::Config::m_vsequence,m_psequence,m_dsequence;
define the order and type of solvers to apply for velocities, positions and drift, see btSoftBody::eVSolver for velocities, and btSoftBody::ePSolver for positions and drift.
为了达到该效果，软体部分主要的参数设置是
m_softBodyWorldInfo.m_gravity.setValue(0,0,0); 把软体世界的重力设为（0，0，0），如果不设为0，又想达到上述效果，目前还不知道可行办法。
sphere->setPose(true, true); 两个参数分别为，是否维持软体的体积和形状
sphere->m_cfg.kVC = 0.001; //Volume conversation，当打开维持体积参数后，该参数用于设置维持系数，[0，1]，越大表示维持程度越大
sphere->m_cfg.kMT = 0.0; //pose matching 当打开维持形状参数后，该参数用于设置维持系数，[0，1]，越大表示维持程度越大
Bullet.cpp
#include <GLUT/glut.h>
#include <cstdlib> /* for exit */
#include <vector>
#include <btBulletDynamicsCommon.h>
#include "BulletSoftBody/btSoftRigidDynamicsWorld.h"
#include "BulletSoftBody/btSoftBodyRigidBodyCollisionConfiguration.h"
#include "BulletSoftBody/btSoftBodyHelpers.h"
#include "BulletSoftBody/btSoftBody.h"
#include "BulletCollision/CollisionDispatch/btSphereSphereCollisionAlgorithm.h"
#include "BulletCollision/NarrowPhaseCollision/btGjkEpa2.h"
#include "LinearMath/btQuickprof.h"
#include "LinearMath/btIDebugDraw.h"
#include "LinearMath/btConvexHull.h"
#include "LinearMath/btAlignedObjectArray.h"
using namespace std;
float zoom = 800.f;
float rotx = 20;
float roty = 0;
float tx = 0;
float ty = 0;
int lastx=0;
int lasty=0;
unsigned char Buttons[3] = {0};
float lightPosition[] = { -200, 300, 300, 1.0f};
float ambientLight[] = { 0.2f, 0.2f, 0.2f, 1.0f };
float diffuseLight[] = { 0.8f, 0.8f, 0.8, 1.0f };
float specularLight[] = { 0.5f, 0.5f, 0.5f, 1.0f };
btSoftRigidDynamicsWorld* mp_btDynamicsWorld = NULL;
btRigidBody *rigid = NULL;
btRigidBody *ground = NULL;
btSoftBodyWorldInfo m_softBodyWorldInfo;
btSoftBody *sphere = NULL;
void InitWorld()
{
btVector3 worldAabbMin(-10000,-10000,-10000);
btVector3 worldAabbMax(10000,10000,10000);
int maxProxies = 100000;
btAxisSweep3* broadphase = new btAxisSweep3(worldAabbMin,worldAabbMax,maxProxies);
m_softBodyWorldInfo.m_broadphase = broadphase;
//
btDefaultCollisionConfiguration* collisionConfiguration = new btSoftBodyRigidBodyCollisionConfiguration();
btCollisionDispatcher* dispatcher = new btCollisionDispatcher(collisionConfiguration);
m_softBodyWorldInfo.m_dispatcher = dispatcher;
btSequentialImpulseConstraintSolver* solver = new btSequentialImpulseConstraintSolver;
mp_btDynamicsWorld = new btSoftRigidDynamicsWorld(dispatcher,broadphase,solver,collisionConfiguration);
m_softBodyWorldInfo.m_sparsesdf.Initialize();
m_softBodyWorldInfo.air_density = (btScalar)1.2;
m_softBodyWorldInfo.water_density = 0;
m_softBodyWorldInfo.water_offset = 0;
m_softBodyWorldInfo.water_normal = btVector3(0,0,0);
mp_btDynamicsWorld->setGravity(btVector3(0,-500,0));
m_softBodyWorldInfo.m_gravity.setValue(0,0,0);
}
void InitObject()
{
//init rigid
//btCollisionShape *collisionShape = new btBoxShape(btVector3(50,50,50));
btCollisionShape *collisionShape = new btSphereShape(50);
//initial position
btVector3 pos = btVector3(40, 300, 40);
btQuaternion qrot(0, 0, 0, 1);
btDefaultMotionState* motion_state = new btDefaultMotionState(btTransform(qrot, pos));
btScalar mass = btScalar(100000);
btVector3 inertia = btVector3(0, 0, 0);//guan xing
collisionShape->calculateLocalInertia(mass, inertia);
rigid = new btRigidBody(mass, motion_state, collisionShape, inertia);
btScalar restitution = btScalar(0.5);
rigid->setRestitution(restitution);
//default 0.5
btScalar friction = btScalar(1);
rigid->setFriction(friction);
mp_btDynamicsWorld->addRigidBody(rigid);
//init ground
btCollisionShape *groundShape = new btBoxShape(btVector3(500,5,500)); //half size
btVector3 groundpos = btVector3(0,0,0);
btQuaternion groundrot(0, 0, 0, 1);
btDefaultMotionState* groundMotion = new btDefaultMotionState(btTransform(groundrot, groundpos));
ground = new btRigidBody(0.0, groundMotion, groundShape);//mass = 0 means it is a static object
btScalar rest = btScalar(1);
ground->setRestitution(rest);
mp_btDynamicsWorld->addRigidBody(ground);
//softbody
sphere = btSoftBodyHelpers::CreateEllipsoid(m_softBodyWorldInfo,
btVector3(0, 60, 0),
btVector3(1, 1, 1)*60,
10000);
sphere->m_cfg.collisions|=btSoftBody::fCollision::VF_SS;
sphere->setTotalMass(1000000,true);
sphere->setPose(true, true);
sphere->m_materials[0]->m_kLST = 1;
//sphere->m_cfg.kVCF = 0;
sphere->m_cfg.kDP = 1;
sphere->m_cfg.kDG = 0;
sphere->m_cfg.kLF = 0;
sphere->m_cfg.kPR = 100;
sphere->m_cfg.kVC = 0.001; //Volume conversation
sphere->m_cfg.kDF = 0;//1
sphere->m_cfg.kMT = 0.0; //pose matching
sphere->m_cfg.kCHR = 0;
sphere->m_cfg.kKHR = 0;
sphere->m_cfg.kSHR = 0;
sphere->m_cfg.kAHR = 0;
mp_btDynamicsWorld->addSoftBody(sphere);
}
void DeleteBullet()
{
//rigid
delete rigid->getMotionState();
mp_btDynamicsWorld->removeRigidBody(rigid);
delete rigid;
rigid = NULL;
//ground
delete ground->getMotionState();
mp_btDynamicsWorld->removeRigidBody(ground);
delete ground;
ground = NULL;
//softbody
mp_btDynamicsWorld->removeSoftBody(sphere);
delete sphere;
sphere = NULL;
//world
delete mp_btDynamicsWorld->getBroadphase();
delete mp_btDynamicsWorld;
mp_btDynamicsWorld = NULL;
}
void DrawGrid(int _halfLen, int _gridNum)
{
glColor3f(1.0f,1.0f,1.0f);
// draw grid
glLineWidth(2);
glBegin(GL_LINES);
for(int i = -_halfLen;i <= _halfLen; i += (_halfLen/_gridNum)) {
glVertex3f(i,0,-_halfLen);
glVertex3f(i,0,_halfLen);
glVertex3f(_halfLen,0,i);
glVertex3f(-_halfLen,0,i);
}
glEnd();
}
void DrawCoordinate(float _flengthX, float _flengthY, float _flengthZ)
{
glLineWidth(5);
glBegin(GL_LINES);
glColor3f(1,0,0);
glVertex3f(0,0,0);
glVertex3f(_flengthX,0,0);
glEnd();
glBegin(GL_LINES);
glColor3f(0,1,0);
glVertex3f(0,0,0);
glVertex3f(0,_flengthY,0);
glEnd();
glBegin(GL_LINES);
glColor3f(0,0,1);
glVertex3f(0,0,0);
glVertex3f(0,0,_flengthZ);
glEnd();
}
void DrawBulletObject()
{
//rigid
btTransform trans = rigid->getWorldTransform();
btScalar m[16];
trans.getOpenGLMatrix(m);
glColor3f(0, 0, 1);
glPushMatrix();
glMultMatrixf((GLfloat*)m);
//glutSolidCube(100); //total length
glutSolidSphere(50,50,50);
glPopMatrix();
//ground
glColor3f(0, 1, 0);
glPushMatrix();
//glTranslatef(0, -50, 0);
glScalef(1, 0.001, 1);
glutSolidCube(1000); //size
glPopMatrix();
//softbody
btTransform meshTransform = sphere->getWorldTransform();
GLfloat tempForm[16];
meshTransform.getOpenGLMatrix(tempForm);
glPushMatrix();
glMultMatrixf(tempForm);
int numFaces = sphere->m_faces.size();
for (int i=0; i< numFaces; i++)
{
btSoftBody::Node* node_0=sphere->m_faces[i].m_n[0];
btSoftBody::Node* node_1=sphere->m_faces[i].m_n[1];
btSoftBody::Node* node_2=sphere->m_faces[i].m_n[2];
btVector3 p0;
p0 = node_0->m_x;
btVector3 p1;
p1 = node_1->m_x;
btVector3 p2;
p2 = node_2->m_x;
//Calculate the normals for the 2 triangles and add on
btVector3 tpt1, tpt2;
tpt1 = p1-p0;
tpt2 = p2-p0;
btVector3 normal= tpt1.cross(tpt2);
glBegin(GL_TRIANGLES);
glNormal3fv(normal);
glColor3f(0,1,1);
glVertex3f(p0.getX()*1,p0.getY()*1,p0.getZ()*1);
glVertex3f(p1.getX()*1,p1.getY()*1,p1.getZ()*1);
glVertex3f(p2.getX()*1,p2.getY()*1,p2.getZ()*1);
glEnd();
}
glPopMatrix();
}
void Simulate()
{
double dt = 1.f/60.0f;
if(mp_btDynamicsWorld)
mp_btDynamicsWorld->stepSimulation(dt,1);
}
//-------------------------------------------------------------------------------
///
void Display()
{
Simulate();
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glTranslatef(0,0,-zoom);
glTranslatef(tx,ty,0);
glRotatef(rotx,1,0,0);
glRotatef(roty,0,1,0);
glLightfv(GL_LIGHT1, GL_AMBIENT, ambientLight);
glLightfv(GL_LIGHT1, GL_DIFFUSE, diffuseLight);
glLightfv(GL_LIGHT1, GL_SPECULAR, specularLight);
glLightfv(GL_LIGHT1, GL_POSITION, lightPosition);
glEnable(GL_LIGHT1);
glEnable(GL_LIGHTING);
glColorMaterial(GL_FRONT_AND_BACK,GL_AMBIENT_AND_DIFFUSE);
glEnable(GL_COLOR_MATERIAL);
DrawBulletObject();
glDisable( GL_LIGHTING );
glDisable(GL_COLOR_MATERIAL);
//DrawGrid(1000, 10);
//DrawCoordinate(1000,1000,1000);
glutPostRedisplay();
glutSwapBuffers();
}
void Init()
{
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClearDepth(1.0f);
glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
glDepthFunc(GL_LEQUAL);
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_NORMALIZE);
InitWorld();
InitObject();
}
void Reshape(int w, int h)
{
// prevent divide by 0 error when minimised
if(w==0)
h = 1;
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45,(float)w/h,0.1,5000);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
//-------------------------------------------------------------------------------
//
void Motion(int x,int y)
{
int diffx=x-lastx;
int diffy=y-lasty;
lastx=x;
lasty=y;
if( Buttons[2] )
{
zoom -= (float) 2* diffx*2;
}
else
if( Buttons[0] )
{
rotx += (float) 1 * diffy;
roty += (float) 1 * diffx;
}
else
if( Buttons[1] )
{
tx += (float) 1 * diffx;
ty -= (float) 1 * diffy;
}
glutPostRedisplay();
}
void Mouse(int b,int s,int x,int y)
{
lastx=x;
lasty=y;
switch(b)
{
case GLUT_LEFT_BUTTON:
Buttons[0] = ((GLUT_DOWN==s)?1:0);
break;
case GLUT_MIDDLE_BUTTON:
Buttons[1] = ((GLUT_DOWN==s)?1:0);
break;
case GLUT_RIGHT_BUTTON:
Buttons[2] = ((GLUT_DOWN==s)?1:0);
break;
default:
break;
}
glutPostRedisplay();
}
void Keyboard(unsigned char key, int x, int y)
{
switch(key) {
case 'q':
case 'Q':
case 27: // ESC key
exit(0);
break;
case 'r':
DeleteBullet();
InitWorld();
InitObject();
break;
default:
break;
}
}
int main(int argc,char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH);
glutInitWindowSize(640,480);
glutInitWindowPosition(100,100);
glutCreateWindow("Bullet Framework");
glutDisplayFunc(Display);
glutReshapeFunc(Reshape);
glutMouseFunc(Mouse);
glutMotionFunc(Motion);
glutKeyboardFunc(Keyboard);
Init();
glutMainLoop();
return 0;
}CMakeLists.txt
cmake_minimum_required (VERSION 2.6)
project(Bullet)
add_executable(Bullet Bullet.cpp)
find_package(OpenGL REQUIRED)
include_directories(${OPENGL_INCLUDE_DIR})
find_package(GLUT REQUIRED)
include_directories(${GLUT_INCLUDE_DIR})
SET(BULLETHEADER "/Users/yang/DEVELOPMENT/ProgramFiles/bullet-2.82-r2704/src")
include_directories("${BULLETHEADER}")
IF(APPLE)
#SET(GUI_TYPE MACOSX_BUNDLE)
FIND_LIBRARY(BULLETDYNAMICS_LIBRARY BulletDynamics)
FIND_LIBRARY(BULLETCOLLISION_LIBRARY BulletCollision )
FIND_LIBRARY(LINEARMATH_LIBRARY LinearMath )
FIND_LIBRARY(BULLETSOFTBODY_LIBRARY BulletSoftBody)
ENDIF (APPLE)
target_link_libraries(Bullet ${GLUT_LIBRARY} ${OPENGL_LIBRARY})
target_link_libraries(Bullet ${BULLETDYNAMICS_LIBRARY} ${BULLETCOLLISION_LIBRARY} ${LINEARMATH_LIBRARY} ${BULLETSOFTBODY_LIBRARY})
Bullet 刚体与软体的碰撞 collisions between rigidbody and softbody in Bullet