使用 OpenGL 的子弹物理

Question

我在我的 opengl 游戏中实现子弹物理时遇到了一些问题。问题是它不想持续更新我的 translatef 值，而只是在最后。 项目符号的代码如下所示：

void CGL::initPhysics( void ) {
broadphase = new btDbvtBroadphase();
collisionConfiguration = new btDefaultCollisionConfiguration();
dispatcher = new btCollisionDispatcher(collisionConfiguration);
solver = new btSequentialImpulseConstraintSolver;
dynamicsWorld = new btDiscreteDynamicsWorld(dispatcher,broadphase,solver,collisionConfiguration);

dynamicsWorld->setGravity(btVector3(0,-10,0));


ballShape = new btSphereShape(1);
pinShape = new btCylinderShape(btVector3(1,1,1));
pinShape->setMargin(0.04);

fallMotionState = new btDefaultMotionState(btTransform(btQuaternion(0,0,0,1),btVector3(0,10,0)));
btScalar mass = 1;
btVector3 fallInertia(0,0,0);
ballShape->calculateLocalInertia(mass,fallInertia);

btCollisionShape* groundShape = new btStaticPlaneShape(btVector3(0,1,0),1);

btDefaultMotionState* groundMotionState = new btDefaultMotionState(btTransform(btQuaternion(0,0,0,1),btVector3(0,-1,0)));
btRigidBody::btRigidBodyConstructionInfo groundRigidBodyCI(0,groundMotionState,groundShape,btVector3(0,0,0));
btRigidBody* groundRigidBody = new btRigidBody(groundRigidBodyCI);
dynamicsWorld->addRigidBody(groundRigidBody);

btRigidBody::btRigidBodyConstructionInfo fallRigidBodyCI(mass,fallMotionState,ballShape,fallInertia);
btRigidBody* fallRigidBody = new btRigidBody(fallRigidBodyCI);
dynamicsWorld->addRigidBody(fallRigidBody);

for (int i=0 ; i<300 ; i++) {
    dynamicsWorld->stepSimulation(1/60.f,10);

    btTransform trans;
    fallRigidBody->getMotionState()->getWorldTransform(trans);

    fallY = trans.getOrigin().getY();
}
state_list.remove( STATE_FALL_BALL );
printf("stoped\n");

}

而开头调用的绘图函数是这样的：

void CGL::fallingBall( void ) {
glPushMatrix();

float colBall2[4] = { 0.0f, 0.0f, 1.0f, 1.0f };
glMaterialfv( GL_FRONT, GL_AMBIENT, colBall2);

glTranslatef(0.0f,fallY,0.0f);

printf("fallY: %f\n",fallY);

glutSolidSphere(1.0f,20,20);

glPopMatrix();

}

问题是它在这个函数的 printf 中显示了正确的值，但是翻译只在开始时被调用，我的意思是我只能看到最后一个状态。

编辑

这是改变的函数和循环。收集我认为它现在应该工作的所有信息，但它没有。它不画任何东西。

initPhysics(){
    for (int i=0 ; i<500 ; i++) 
    {
        draw();

    }
    state_list.remove( STATE_FALL_BALL );
    printf("stoped\n");
}

void CGL::draw(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
            current_time = getTime();
            since_update = current_time - last_update;
            printf("time: %f\n",since_update);
            if(since_update>timestep)
            {
                dynamicsWorld->stepSimulation(timestep,10);
                last_update = current_time;
            }
            btTransform trans;
            fallRigidBody->getMotionState()->getWorldTransform(trans);

            fallY = trans.getOrigin().getY();
            fallingBall();
            printf("fallY: %f\n",fallY);
glFlush();
    }

开始的变量声明看起来像这样：

last_update = 0;
timestep = 100;
current_time = 0;
since_update = 0;

Answer 1

看起来有点杂乱无章。我想在不深入研究多线程的情况下解决当前问题的基本错误是这样做：

//pseudo-code to get the idea
void draw(){
    // clear Buffers and setup matricies
    ....
    //calculate the time that has pased since the last time that the physics have been calculated
    time_t current_time = getCurrentTime();
    time_t since_update = current_time - last_update;

    //if enough time has passed since the last redraw calculate physics
    if(since_update>timestep)
    {
        dynamicsWorld->stepSimulation(timestep,10);
        last_update = current_time;
    }
    btTransform trans;
    fallRigidBody->getMotionState()->getWorldTransform(trans);

    fallY = trans.getOrigin().getY();

    //draw various object
    ....
    fallingBall();
    //swap buffers or flush()
    glSwapBuffers();
}

除非有明确的原因直接使用 OpenGL，否则我建议您使用更高级别的工具包。还有通常的免责声明，即您当前使用的是旧版本的 OpenGL。