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N体模拟幻影力

game-physics simulation java

PeterLikesCode · 技术社区 · 8 年前

在我的n体模拟中,大约有1k个粒子在周围飞行。我把位置存储为浮动。我有一个问题是每次运行代码时,当两个粒子真正接近彼此(本质上相同的位置)时,它们是极其加速的。通常情况下,粒子的行为是平滑的。

if((planet.position.x != otherPlanet.position.x && planet.position.y != otherPlanet.position.y) && !otherPlanet.delete)
        {
            //First we get the x,y and magnitudal distance between the two bodies.
            float xDist = (otherPlanet.position.x - planet.position.x);
            float yDist = (otherPlanet.position.y - planet.position.y);
            float dist = Vector2Math.distance(planet.position, otherPlanet.position);

            //Now we compute first the total and then the component forces
            //Depending on choice, use r or r^2
            float force = Constants.GRAVITATIONAL_CONSTANT * ((planet.mass*otherPlanet.mass)/(dist*dist)); 
            float forceX = force * xDist/dist;
            float forceY = force * yDist/dist;

            //Given the component forces, we construct the force vector and apply it to the body.
            Vector2 forceVec = new Vector2(forceX, forceY);
            planet.force = Vector2Math.add(planet.force, forceVec);
            otherPlanet.force = Vector2Math.subtract(otherPlanet.force, forceVec);
        }

我还没有找到关于这个话题的任何东西,但这是我做错了还是我必须实现最大加速度或粒子之间的最小距离?

1 回复 | 直到 8 年前

Lone_Coder 8 年前

模拟世界和真实世界有点不同,为了使模拟效果好,我们需要增加一些限制。

问题:

当两个粒子非常接近时,它们就会爆炸以惊人的速度向外移动。

原因

原因是简单的重力是相反的与两个物体之间的距离平方成正比。当两个物体靠得太近,半径(它们之间的距离)变得很小作用在他们身上的力变得非常大。

解决方案

对两个粒子的接近程度添加一个虚拟限制。虚拟极限我是说极限只在数值上,而不是在模拟。例如,如果它们之间的距离小于5(A 阈值)将距离设置为5。

代码中的更改

if((planet.position.x != otherPlanet.position.x && planet.position.y != otherPlanet.position.y) && !otherPlanet.delete)
        {
            //First we get the x,y and magnitudal distance between the two bodies.
            float xDist = (otherPlanet.position.x - planet.position.x);
            float yDist = (otherPlanet.position.y - planet.position.y);
             // add a limit to xDist and yDist
             if(xDist<5)
                xDist=5;
             if(yDist<5)
                yDist=5;
            float dist = Vector2Math.distance(planet.position, otherPlanet.position);

            //Now we compute first the total and then the component forces
            //Depending on choice, use r or r^2
            float force = Constants.GRAVITATIONAL_CONSTANT * ((planet.mass*otherPlanet.mass)/(dist*dist)); 
            float forceX = force * xDist/dist;
            float forceY = force * yDist/dist;

            //Given the component forces, we construct the force vector and apply it to the body.
            Vector2 forceVec = new Vector2(forceX, forceY);
            planet.force = Vector2Math.add(planet.force, forceVec);
            otherPlanet.force = Vector2Math.subtract(otherPlanet.force, forceVec);
        }

当然,您希望将该5更改为适合您模拟的值。