javascript实现多边形碰撞检测

javascript多边形碰撞检测

原理就是 循环每个顶点判断是不是在多边形内

const app = new pixi.application({ antialias: true });
document.body.appendchild(app.view);

const graphics = new pixi.graphics();


// draw polygon
const path = [600, 370, 700, 460, 780, 420, 730, 570, 590, 520];

graphics.linestyle(0);
graphics.beginfill(0x3500fa, 1);
graphics.drawpolygon(path);
graphics.endfill();

app.stage.addchild(graphics);

 var xuanzhuan = pixi.sprite.from('/moban/images/share.jpg');
 xuanzhuan.width=120;
 xuanzhuan.height=120;
 xuanzhuan.x=13;
 xuanzhuan.y=33;
  app.stage.addchild(xuanzhuan);


  xuanzhuan.interactive = true;

  xuanzhuan.buttonmode = true;
   xuanzhuan
    .on('pointerdown', ondragstart)
    .on('pointerup', ondragend)
    .on('pointerupoutside', ondragend)
    .on('pointermove', ondragmove);

  function ondragstart(event) {
  // store a reference to the data
  // the reason for this is because of multitouch
  // we want to track the movement of this particular touch
  this.data = event.data;
  this.alpha = 0.5;
  this.dragging = true;
}

function ondragend() {
  this.alpha = 1;
  this.dragging = false;
  // set the interaction data to null
  this.data = null;
}
   var  pospolygon=[];
     var dianlist={};
    dianlist['x']=600;
    dianlist['y']=370; 
    pospolygon.push(dianlist)
  var dianlist={};
    dianlist['x']=700;
    dianlist['y']=460; 
    pospolygon.push(dianlist)  
  var dianlist={};
    dianlist['x']=780;
    dianlist['y']=420; 
    pospolygon.push(dianlist)   
  var dianlist={};
    dianlist['x']=730;
    dianlist['y']=570; 
   pospolygon.push(dianlist) 
  var dianlist={};
    dianlist['x']=590;
    dianlist['y']=520; 
    pospolygon.push(dianlist)
function ondragmove() {
  if (this.dragging) {
    const newposition = this.data.getlocalposition(this.parent);
    this.x = newposition.x;
    this.y = newposition.y;

    var baoweihe=this.getbounds();
    var youxiajiaox=baoweihe.x+baoweihe.width;
    var youxiajiaoy=baoweihe.y+baoweihe.height;

    var poslist=[];
     var pos={};
    pos['x']=baoweihe.x;
    pos['y']=baoweihe.y;    
    poslist.push(pos);      

  var pos={};
    pos['x']=youxiajiaox;
    pos['y']=baoweihe.y;    
    poslist.push(pos);      
    var pos={};
    pos['x']=youxiajiaox;
    pos['y']=youxiajiaoy;    
    poslist.push(pos);

    var pos={};
    pos['x']=baoweihe.x;
    pos['y']=youxiajiaoy;    
    poslist.push(pos);    

     
  
    var ispengzhuang=polygoninpolygon(poslist, pospolygon,5);
    if(ispengzhuang){
      alert('碰撞了');
    }


  }
}

function polygoninpolygon(pospolygona, pospolygonb, count){
  console.log(pospolygona);
    var count1=pospolygona.length;
   for(var i=0;i<count1;i++ ){
    var pos=pospolygona[i];
      console.log(pos);
     var ispengzhuang=pointinpolygon( pos, pospolygonb, count);
     if(ispengzhuang){
      alert('碰撞了')
     }
   }
}

function pointinpolygon( pos, pospolygonb, count)
{
  var cross = 0; //交点个数
    
  for( var i = 0; i < count; i++ )
  {
    var p1 = pospolygon[i];
    var p2 = pospolygon[(i + 1) % count]; //下一个节点
 
    // p1p2这条边与水平线平行
    if( p1.y == p2.y )
      continue;
 
    // 交点在p1p2的延长线上
    if( pos.y < math.min( p1.y, p2.y ) )
      continue;
 
    // 交点在p1p2的延长线上
    if( pos.y > math.max( p1.y, p2.y ) )
      continue;
      
    // 计算交点 x 左边 ： (p2.y - p1.y)/(p2.x - p1.x) = (y - p1.y)/(x - p1.x)
    // 直线 k 值相等， 交点y = pos.y
    let x = (pos.y - p1.y) * (p2.x - p1.x) / (p2.y - p1.y) + p1.x
    // 只统计单边交点，即点的正向方向
    if(x > pos.x)
      cross ++;
  }
 
  return cross % 2 == 1;
}

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