最小限の実行可能な例
時間の関数で異なる高さから落下する2つの球。
それらは異なる高さで始まるので、それらは異なる時間に地面に当たります。
地面の衝突を検出し、いつどの球が地面に触れたかを印刷します。
stdoutのgnuplot視覚化：
方法を見る：
- 1つの球が地面にぶつかると、ピンク色の四角い衝突インジケータが
1
- 他の球が地面にぶつかると、グリーン
Xは1
コード：
#include <cstdio>
#include <cstdlib>
#include <map>
#include <vector>
#include <btBulletDynamicsCommon.h>
#define PRINTF_FLOAT "%7.3f"
constexpr float gravity = -10.0f;
constexpr float timeStep = 1.0f / 60.0f;
constexpr float groundRestitution = 0.9f;
constexpr float objectRestitution = 0.9f;
constexpr int maxNPoints = 500;
constexpr float initialXs[] = { 0.0f, 5.0f };
constexpr float initialYs[] = { 10.0f, 5.0f };
constexpr size_t nObjects = sizeof(initialYs) / sizeof(*initialYs);
std::map<const btCollisionObject*,std::vector<btManifoldPoint*>> objectsCollisions;
void myTickCallback(btDynamicsWorld *dynamicsWorld, btScalar timeStep) {
objectsCollisions.clear();
int numManifolds = dynamicsWorld->getDispatcher()->getNumManifolds();
for (int i = 0; i < numManifolds; i++) {
btPersistentManifold *contactManifold = dynamicsWorld->getDispatcher()->getManifoldByIndexInternal(i);
auto *objA = contactManifold->getBody0();
auto *objB = contactManifold->getBody1();
auto& collisionsA = objectsCollisions[objA];
auto& collisionsB = objectsCollisions[objB];
int numContacts = contactManifold->getNumContacts();
for (int j = 0; j < numContacts; j++) {
btManifoldPoint& pt = contactManifold->getContactPoint(j);
collisionsA.push_back(&pt);
collisionsB.push_back(&pt);
}
}
}
int main() {
int i, j;
btDefaultCollisionConfiguration *collisionConfiguration
= new btDefaultCollisionConfiguration();
btCollisionDispatcher *dispatcher = new btCollisionDispatcher(collisionConfiguration);
btBroadphaseInterface *overlappingPairCache = new btDbvtBroadphase();
btSequentialImpulseConstraintSolver* solver = new btSequentialImpulseConstraintSolver;
btDiscreteDynamicsWorld *dynamicsWorld = new btDiscreteDynamicsWorld(
dispatcher, overlappingPairCache, solver, collisionConfiguration);
dynamicsWorld->setGravity(btVector3(0, gravity, 0));
dynamicsWorld->setInternalTickCallback(myTickCallback);
btAlignedObjectArray<btCollisionShape*> collisionShapes;
// Ground.
{
btTransform groundTransform;
groundTransform.setIdentity();
groundTransform.setOrigin(btVector3(0, 0, 0));
btCollisionShape* groundShape;
groundShape = new btStaticPlaneShape(btVector3(0, 1, 0), -1);
collisionShapes.push_back(groundShape);
btDefaultMotionState* myMotionState = new btDefaultMotionState(groundTransform);
btRigidBody::btRigidBodyConstructionInfo rbInfo(0, myMotionState, groundShape, btVector3(0, 0, 0));
btRigidBody* body = new btRigidBody(rbInfo);
body->setRestitution(groundRestitution);
dynamicsWorld->addRigidBody(body);
}
// Objects.
for (size_t i = 0; i < nObjects; ++i) {
btCollisionShape *colShape;
colShape = new btSphereShape(btScalar(1.0));
collisionShapes.push_back(colShape);
btTransform startTransform;
startTransform.setIdentity();
startTransform.setOrigin(btVector3(initialXs[i], initialYs[i], 0));
btVector3 localInertia(0, 0, 0);
btScalar mass(1.0f);
colShape->calculateLocalInertia(mass, localInertia);
btDefaultMotionState *myMotionState = new btDefaultMotionState(startTransform);
btRigidBody *body = new btRigidBody(btRigidBody::btRigidBodyConstructionInfo(
mass, myMotionState, colShape, localInertia));
body->setRestitution(objectRestitution);
dynamicsWorld->addRigidBody(body);
}
// Main loop.
std::printf("step body x y z collision2 collision1\n");
for (i = 0; i < maxNPoints; ++i) {
dynamicsWorld->stepSimulation(timeStep);
for (j = dynamicsWorld->getNumCollisionObjects() - 1; j >= 0; --j) {
btCollisionObject *obj = dynamicsWorld->getCollisionObjectArray()[j];
btRigidBody *body = btRigidBody::upcast(obj);
btTransform trans;
if (body && body->getMotionState()) {
body->getMotionState()->getWorldTransform(trans);
} else {
trans = obj->getWorldTransform();
}
btVector3 origin = trans.getOrigin();
std::printf("%d %d " PRINTF_FLOAT " " PRINTF_FLOAT " " PRINTF_FLOAT " ",
i, j, origin.getX(), origin.getY(), origin.getZ());
auto& manifoldPoints = objectsCollisions[body];
if (manifoldPoints.empty()) {
std::printf("0");
} else {
std::printf("1");
}
puts("");
}
}
// Cleanup.
for (i = dynamicsWorld->getNumCollisionObjects() - 1; i >= 0; --i) {
btCollisionObject* obj = dynamicsWorld->getCollisionObjectArray()[i];
btRigidBody* body = btRigidBody::upcast(obj);
if (body && body->getMotionState()) {
delete body->getMotionState();
}
dynamicsWorld->removeCollisionObject(obj);
delete obj;
}
for (i = 0; i < collisionShapes.size(); ++i) {
delete collisionShapes[i];
}
delete dynamicsWorld;
delete solver;
delete overlappingPairCache;
delete dispatcher;
delete collisionConfiguration;
collisionShapes.clear();
}
Bullet 2.83、Ubuntu 15.10でテスト済み。
GitHubアップストリーム：https : //github.com/cirosantilli/cpp-cheat/blob/d7b70153b8f86b5864c22fbc6f7005049a93491f/bullet/which_collision.cpp