create box around line

Hello! I need your help!

i have a perlin noise particle funktion, where every particle connects with their nearest neighbour. the connection, which is currently a line, should be a box, to have it as a volume. it would be awesome if you guys can help me!!!! //line from one vector to his nearest neighbor line(pos.x, pos.y , pos.z, npos.x, npos.y, npos.z);

    import peasy.test.*;
    import peasy.org.apache.commons.math.*;
    import peasy.*;
    import peasy.org.apache.commons.math.geometry.*;


    float depth = 500;
    PVector[] nOffset;
    float nScale = 0.01;
    float stepSize = 3;

    ArrayList<Particle> particles;
    ArrayList<Connection> cn=new ArrayList<Connection>();

     PeasyCam cam;

    void setup(){
      size(1500,1000, P3D);
      frameRate(25);
        cam=new PeasyCam(this, 300);


      nOffset = new PVector[3];
      for(int i = 0; i < 3; i++){
        nOffset[i] = new PVector(random(1), random(10000), random(10000));
      }
      particles = new ArrayList<Particle>();
      for(int i = 0; i <300; i++){
        particles.add(new Particle());
      }

      noFill();
      background(0);
    }

    void draw(){

      background(0);
      stroke(255);
      for(Particle p: particles){p.update();}
      for (Connection c : cn) c.display();
      stroke(255);
      translate(750,700,200);
      box(1500,1500,400);


     if (frameCount%10==0)for (Particle p : particles)p.connect();
    }

     class Particle {

      PVector pos;

      Particle() {
        pos = new PVector(random(1500), random(1500), random(400));
      }

      void update() {
        float x = pos.x + map(noise(nOffset[0].x + pos.x * nScale, nOffset[0].y + pos.y * nScale, nOffset[0].z + pos.z * nScale), 0, 1, -stepSize, stepSize);
        float y = pos.y + map(noise(nOffset[1].x + pos.x * nScale, nOffset[1].y + pos.y * nScale, nOffset[1].z + pos.z * nScale), 0, 1, -stepSize, stepSize);
        float z = pos.z + map(noise(nOffset[2].x + pos.x * nScale, nOffset[2].y + pos.y * nScale, nOffset[2].z + pos.z * nScale), 0, 1, -stepSize, stepSize);
        PVector npos = new PVector(x, y, z);
        pushMatrix();
        //translate(0, 0, 0);
        //line(pos.x, pos.y , pos.z, npos.x, npos.y, npos.z);
        popMatrix();
        if ((0 <= npos.x && npos.x <1500 && 0 <= npos.y && npos.y <1500 && 0 <= npos.z && npos.z < 400) &&
          (random(1) < 0.995)) {
          pos = npos;
        } else {
          pos = new PVector(random(1500), random(1500), random(400));
        }
      }


      void connect() {

        for (Particle p : particles) {


          if (p.pos.dist(pos)<150&&p!=this)cn.add(new Connection(p.pos, this.pos));//check for any particles closer than 200, if there are any add a new Connection by providing two positions
        }
      }
    }

    class Connection {// this class describes the connections between particles, "connect" function inside of the "Particle" class creates new Connection objects

      PVector pos, npos;//a connection needs a beginning and end vector

      Connection(PVector p1, PVector p2) {// in order to create a connection, we need to provide two vectors... check "connect" function inside of the "Particle" class
        pos=p1.get();
        npos=p2.get();
      }

      void display() {
        stroke(255, 100);
        strokeWeight(0.3);

        line(pos.x, pos.y , pos.z, npos.x, npos.y, npos.z);   //line from one vector to his nearest neighbor


      }
    }