TimeStep请勿迭代| Box2D

Question

在多年的缺席之后，我又回到了box2d，我想从零开始。最重要的是，这次决定使用C++版本(过去使用Javascript版本)

由于某种原因，box2d.org中描述的第一个程序不能正常运行。当我编译它时，我没有得到任何错误，但是结果是错误的。

结果是0.00 4.00 0.00，并且保持不变。但是随着时间步长的每次迭代，position.x.y应该会减小(position.x .x和angle应该保持不变)

#include "include/box2d/box2d.h"
#include <iostream>
#include <stdio.h>

    
int main(){
  b2Vec2 gravity(0.0f, -10.0f); // define the gravity vector
  b2World world(gravity);       //create the world object

//Creating static Ground Body
  b2BodyDef groundBodyDef;      //body definition
    groundBodyDef.position.Set(0.0f, -10.0f);

  b2Body* groundBody = world.CreateBody(&groundBodyDef); // body definition is passed to the world object to create the ground body

  b2PolygonShape groundBox;    //create a ground polygon.
    groundBox.SetAsBox(50.0f, 10.0f);   //We use the SetAsBox shortcut to form the ground polygon into a box shape

  groundBody->CreateFixture(&groundBox, 0.0f);  //creating the shape fixture

//Creating Dynamic Body
  b2BodyDef bodyDef;
  bodyDef.type = b2_dynamicBody;  //By default bodies are static, so we should set the b2BodyType at construction time to make the body dynamic
  bodyDef.position.Set(0.0f, 4.0f);
  b2Body* body = world.CreateBody(&bodyDef);

  b2PolygonShape dynamicBox;    //create a box shap
  dynamicBox.SetAsBox(1.0f, 1.0f);
//A dynamic body should have at least one fixture with a non-zero density. Otherwise you will get strange behavior.
  b2FixtureDef fixtureDef;    // fixture definition using the box
  fixtureDef.shape = &dynamicBox;
  fixtureDef.density = 1.0f;
  fixtureDef.friction = 0.3f;

  float timeStep = 1.0f / 60.0f;  //Integrators simulate the physics equations at discrete points of time -> ie timeStep

  int32 velocityIterations = 6;
  int32 positionIterations = 2;

  for (int32 i = 0; i < 60; ++i)  {
      world.Step(timeStep, velocityIterations, positionIterations);
      b2Vec2 position = body->GetPosition();
      float angle = body->GetAngle();
      printf("%4.2f %4.2f %4.2f\n", position.x, position.y, angle);
  }

      //return 0;
}

为noobie的问题道歉，但找不到我的错误。我几乎要复制粘贴所有的东西！

Answer 1

我实际上忘记了包含body->CreateFixture(&fixtureDef)；