IT Technology

计算点到直线的距离

2D 中 (C)
参考:https://www.cnblogs.com/yushuo/p/9304218.html

//点PCx,PCy到线段PAx,PAy,PBx,PBy的距离
double GetNearestDistance(double PAx, double PAy,double PBx, double PBy,double PCx, double PCy)
{     
    double a,b,c;  
    a=getDistanceBtwP(PAy,PAx,PBy,PBx);//经纬坐标系中求两点的距离公式
    b=getDistanceBtwP(PBy,PBx,PCy,PCx);//经纬坐标系中求两点的距离公式
    c=getDistanceBtwP(PAy,PAx,PCy,PCx);//经纬坐标系中求两点的距离公式
    if(b*b>=c*c+a*a)return c;   
    if(c*c>=b*b+a*a)return b;  
    double l=(a+b+c)/2;     //周长的一半   
    double s=sqrt(l*(l-a)*(l-b)*(l-c));  //海伦公式求面积 
    return 2*s/a;   
}

3D 中(C#)
参考:https://www.jianshu.com/p/8ba826e6208a

public static float distancePoint2Line(Vector3 point, Vector3 linePoint1, Vector3 linePoint2)
{
    float fProj = Vector3.Dot(point - linePoint1, (linePoint1 - linePoint2).normalized);
    return Mathf.Sqrt((point - linePoint1).sqrMagnitude - fProj * fProj);
}

ubuntu 18.04中netplan配置pre-up和post-down

  1. netplan 自身配置文件/etc/netplan/50-cloud-init.yaml
network:
    version: 2
    renderer: networkd
    ethernets:
        ens3:
            addresses:
            - 154.204.42.134/24
            gateway4: 154.204.42.254
            match:
                macaddress: fa:16:3e:b9:65:3b
            nameservers:
                addresses:
                - 8.8.8.8
                - 8.8.4.4
            set-name: ens3

应用修改

sudo netplan apply

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Unity 摄像机射线碰撞

需要对象挂有Collider组件才能计算射线,某些情况下不适用。

if (Input.GetMouseButtonDown(0))
{
    Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition); //从摄像机发出到点击坐标的射线
    RaycastHit hit;
    if (Physics.Raycast(ray, out hit)) //需要有Collider组件才能碰撞到
    {
        Debug.Log(hit.point);//碰撞坐标
    }
}

Unity 点与平面交点计算函数

参考
https://blog.csdn.net/abcjennifer/article/details/6688080

public static class MyUtils
{
    /*
     * 求一条直线与平面的交点
     * [param] planeVector, 平面的法线向量.
     * [param] planePoint, 平面经过的一点坐标.
     * [param] lineVector, 直线的方向向量.
     * [param] linePoint, 直线经过的一点坐标.
     * [returns] 是否想交, rtn 是交点坐标.
     */
    public static bool PlaneLineIntersectPoint(ref Vector3 planeVector, ref Vector3 planePoint, ref Vector3 lineVector, ref Vector3 linePoint, out Vector3 rtn)
    {
        float vp1, vp2, vp3, n1, n2, n3, v1, v2, v3, m1, m2, m3, t, vpt;
        vp1 = planeVector.x;
        vp2 = planeVector.y;
        vp3 = planeVector.z;
        n1 = planePoint.x;
        n2 = planePoint.y;
        n3 = planePoint.z;
        v1 = lineVector.x;
        v2 = lineVector.y;
        v3 = lineVector.z;
        m1 = linePoint.x;
        m2 = linePoint.y;
        m3 = linePoint.z;

        vpt = v1 * vp1 + v2 * vp2 + v3 * vp3; //点乘
        //首先判断直线是否与平面平行(正确的浮点判断0方式)
        if (Math.Abs(vpt) <= 0.000001f)
        {
            rtn.x = rtn.y = rtn.z = 0;
            return false;
        }

        t = ((n1 - m1) * vp1 + (n2 - m2) * vp2 + (n3 - m3) * vp3) / vpt;
        rtn.x = m1 + v1 * t;
        rtn.y = m2 + v2 * t;
        rtn.z = m3 + v3 * t;
        return true;
    }
}