2

我正在尝试使用verlet 集成来制作软体球体。

我基本上创建了一个网格并通过弹簧附加每个顶点。我正在使用three.js 来渲染球体。我相信一切正常，但我不确定如何获得预期的结果。如果连接太弱，我的球就会塌陷，如果太硬，我的球就会爆炸。似乎有些不对劲。问题发生在物体掉落并撞到地面的那一刻。我将发布我的代码的主要部分，但是我不确定我的方法是否有效并且可以用来产生我想要的结果。

function verletStick3D(p1, p2, distance, rigid){


    this.type = "stick";
    this.p1 = p1;
    this.p2 = p2; 
    this.distance = distance;
    this.rigid = rigid;
    this.update = function(){

        var dx = this.p1.x - this.p2.x;
        var dy = this.p1.y - this.p2.y;
        var dz = this.p1.z - this.p2.z;
        var distance = Math.sqrt(dx * dx + dy * dy + dz * dz);
        var difference = this.distance - distance;
        var percent = difference / distance / 2;
        var offsetX = dx * percent * this.rigid;
        var offsetY = dy * percent * this.rigid;
        var offsetZ = dz * percent * this.rigid;
        this.p1.x += offsetX;
        this.p1.y += offsetY;
        this.p1.z += offsetZ;
        this.p2.x -= offsetX;
        this.p2.y -= offsetY;
        this.p2.z -= offsetZ;

    }
}

function verletPoint3D(x, y,z, maxX, maxZ, bounce = 0.9, friction = 

1.0, gravity = {x:0, y:-0.03, z:0}){
    y = y + 10;
    this.type = "point";
    this.x=x; 
    this.y=y;
    this.z=z;
    this.xOld=x;
    this.yOld=y;
    this.zOld=z;
    this.bounce = bounce;
    this.friction = friction;
    this.gravity = gravity;
    this.update = function(){
        var vx = (this.x - this.xOld) * this.friction;
        var vy = (this.y - this.yOld) * this.friction;
        var vz = (this.z - this.zOld) * this.friction;
        this.xOld = this.x;
        this.yOld = this.y;
        this.zOld = this.z;
        this.x += vx;
        this.y += vy;
        this.z += vz;
        this.y += this.gravity.y;
        this.x += this.gravity.x;
        this.z += this.gravity.z;



    }
    this.setGravity = function(gravity){
        this.gravity = gravity;
    }
    this.constrain = function(){
        var vx = (this.x - this.xOld) ;
        var vy = (this.y - this.yOld) ;

        if(this.x  > this.maxX){
            this.x = width;
            this.xOld = this.x + vx * this.bounce;
        }
        if(this.x < this.minX){
            this.x ;
            this.xOld = this.x + vx * this.bounce;
        }
        if(this.z > this.maxZ ){
            this.z = height ;
            this.zOld = this.z + vz * this.bounce;

        }
        if(this.z  < this.minZ){
            this.z = 0;
            this.zOld = this.z + vz * this.bounce;
        }
        if(this.y  < 0){
            this.y = 0;
            this.yOld = this.y + vy * this.bounce;
        }

    }
}

function verletFromMesh(vertices, faces, maxX, maxY){
    var points  = [];
    for(var i = 0; i < vertices.length; i++){

        var p = new verletPoint3D(vertices[i].x, vertices[i].y, vertices[i].z, maxX, maxY, 0.9, 0.9);
        points.push(p);

    }

    var springs = []
    /*
    for(var i = 0; i < faces.length; i++){
        var face = faces[i];
        var p1 = face.a;
        var p2 = face.b;
        var p3 = face.c;
        springs.push(new verletStick( p1,p2, distance3D(p1, p2), 1.0) )
        springs.push(new verletStick( p2,p3, distance3D(p2, p3), 1.0) )
        springs.push(new verletStick( p3,p1, distance3D(p3, p1), 1.0) )
    }*/
    for(var i = 0; i < points.length; i++){
        var p1 = points[i];
        for(var j= i+1; j < points.length; j++){
            var p2 = points[j];
            if(p1.x == p2.x && p1.y == p2.y && p1.z == p2.z)
                continue;
            var dist = distance3D(p1, p2)

            springs.push(new verletStick3D( p1,p2, dist, 1.0) )


        }


    }


    return new verletObj(points, springs);
}
4

1 回答 1

1

嗯，很难确切地看出你哪里出错了，但对我来说，你的弹簧似乎无法扭转运动。这将根据他们的力量导致爆炸/崩溃。我强烈建议尝试明确限制它们对球体的影响，希望这将帮助您进一步调试此问题。

您的数学运算方式，尤其是在设置偏移量时，dx * percent * this.rigid;使这些动态力看起来像是静态地表现，因此发挥的作用太大了。

ps：你看过这个帖子吗？这是关于摩擦的，但我认为这里的答案是可以引用的：

只需在指向与运动相反的方向的移动物体上引入一个小的恒定加速度。并确保它实际上不能逆转运动；如果您在积分步骤中检测到这一点，只需将速度设置为零。

希望这能以某种方式使您朝着正确的方向前进。

于 2017-08-10T16:07:26.720 回答