线相交多边形不起作用

Question

我正在使用libgdx编写一个小型太空游戏，该船发射激光，我需要计算它何时（如果有的话）与聚合物（小行星）相交。这样我就可以阻止激光穿过物体，并实际与它们发生碰撞。我的代码似乎在某些时候有效，而在其他方面完全失败。我无法弄清楚是什么导致它失败，我很确定这不是我的多边形定义是错误的，因为有时它会在边缘工作，有时候不是，没有一致性。

我已经检查了我的光线的痕迹（严格来说是一条线）而且它是现货，所以不是那样。这是代码，我将尝试解释我之后所做的事情。

//Beam Collisions

//If the beam isn't being fired, return
if(!active) return;

//Storing all the points to be checked on the beam, I've checked the all seem accurate, and have draw a line between them and they match the laser.   
List<Vector2> beamPoints = new ArrayList<Vector2>();

//Step allows me to reduce the number points I test when it finally works
int step = 1;
for(int n=0;n<maxHeight;n+=step){

        //Rotation is the rotation of the ship. I add 90 to it so the angle of my vector is from the x-axis. 
        //shipX is the world coords of the ship. x is the relative start point of the laser to the ship.
        //shipX refers to the centre of the ship, not the corner of the graphic.
        beamPoints.add(
            new Vector2(shipX+x+(float)(n*Math.cos(Math.toRadians(rotation+90))),
                  shipY+y+(float)(n*Math.sin(Math.toRadians(rotation+90)))));
}

//Here I cycle through the entities to test if they collide. Currently the only entities are asteroids.   
for(Entity e : entities){
   //Skip over the entity if it's outside the render range or it has no geometry.
   if(!e.inRenderRange || e.getGeometry()==null) continue;

        //A list to store all the vertices of that asteroids geometry.
        List<Vector2> verts = new ArrayList<Vector2>();
        for(Vector2 v : e.getGeometry()){

                //Determining the x and y of the vertice to store. e.x is the asteroids world coords, I subtract the half the imageWidth because it's position is stored as the centre of the graphic.
                //I then add the relative x and y of the vertex.
                //I've turned off rotation for the asteroids, so that's not a problem.
                float nx = (e.x-e.imageWidth/2)+v.x;
                float ny = (e.y-e.imageHeight/2)+v.y;

                verts.add(new Vector2(nx,ny));

   }

    //Testing each of the points on the beam to see if there are in the poly.
    for(int j=0;j<beamPoints.size();j++){

        //Using Intersector, a class in Libgdx, I can safely assume this is working fine. 
        if(Intersector.isPointInPolygon(verts, beamPoints.get(j))){

            /Changing the height (should be labelled length) of the beam to be that at which it collides. Step is one, so doesn't matter for now.
            height = j*step;
            break;
      }
   }


}

我还应该从下面的图片中指出，通过激光我的意思是明亮的核心，我没有烦恼它的发光，这没有错，我还没有完成它。

我希望这是足够的代码，如果有什么我可以提供请问;我很乐意为你提供任何帮助。

干杯全部

Answer 1

你真的在你的线路上产生大量离散点，然后用inPolygon检查来测试每一点吗？这不是解决这个问题的好方法。

您的多边形由线段组成。你真正需要做的就是测试一个线段与你的光束相交，然后找到最近交点的实体。

关于线段交叉点的计算有很多信息。

这是来自SO的内容：How do you detect where two line segments intersect?