libgdx学习记录26——Polygon多边形碰撞检测

libgdx中Math封装了Polygon这个类，它是由多个定点进行描述实现的，在进行物体间的碰撞时，物体轮廓有时候是不规则的，这时候可以用一个多边形勾勒出其大概的轮廓，对其进行模拟。

Polygon内部自带是否包含点contains这个函数，通过这个函数我们可以判断两个多变行是否碰撞，即检测两个多边形的每个点是否在另一个多边形中。

检测代码：

     public static boolean isOverlap(Polygon polygon1, Polygon polygon2){
         for(int i=0; i<polygon2.getVertices().length; i+=2){
             if( polygon1.contains(polygon2.getVertices()[i], polygon2.getVertices()[i+1]) ){
                 return true;
             }
         }
         for(int i=0; i<polygon1.getVertices().length; i+=2){
             if( polygon2.contains(polygon1.getVertices()[i], polygon1.getVertices()[i+1]) ){
                 return true;
             }
         }
         return false;
     }

实例代码：

 package com.fxb.Gam003;

 import com.badlogic.gdx.ApplicationAdapter;
 import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.InputAdapter;
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.GL10;
 import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
 import com.badlogic.gdx.graphics.glutils.ShapeRenderer.ShapeType;
 import com.badlogic.gdx.math.Polygon;
 import com.badlogic.gdx.math.Vector2;

 public class Lib051_Polygon extends ApplicationAdapter{

     Polygon polygon1, polygon2;
     ShapeRenderer rend;
     float[] vertices1, vertices2;
     Vector2 point = new Vector2(100, 50);

     InputAdapter adapter = new InputAdapter(){
         @Override
         public boolean touchDown(int screenX, int screenY, int pointer, int button) {
             for(int i=0; i<polygon2.getVertices().length; i+=2){
                 polygon2.getVertices()[i  ] += screenX - point.x;
                 polygon2.getVertices()[i+1] += Gdx.graphics.getHeight()-screenY - point.y;
             }
             polygon2.dirty();

             point.set(screenX, Gdx.graphics.getHeight()-screenY);
             //polygon2.setVertices(new float[]{ 100+point.x, 50+point.y, 200+point.x, 70+point.y, 300+point.x, 150+point.y, 150+point.x, 100+point.y});

             return true;
         }

     };

     @Override
     public void create() {
         // TODO Auto-generated method stub
         super.create();

         polygon1 = new Polygon();
         vertices1 = new float[]{ 100, 100, 200, 100, 300, 300, 100, 200 };
         polygon1.setVertices(vertices1);

         vertices2 = new float[]{ 100, 50, 200, 70, 300, 150, 150, 100};
         polygon2 = new Polygon(vertices2);

         rend = new ShapeRenderer();
         Gdx.input.setInputProcessor(adapter);
     }

     public static boolean isOverlap(Polygon polygon1, Polygon polygon2){
         for(int i=0; i<polygon2.getVertices().length; i+=2){
             if( polygon1.contains(polygon2.getVertices()[i], polygon2.getVertices()[i+1]) ){
                 return true;
             }
         }
         for(int i=0; i<polygon1.getVertices().length; i+=2){
             if( polygon2.contains(polygon1.getVertices()[i], polygon1.getVertices()[i+1]) ){
                 return true;
             }
         }
         return false;
     }

     @Override
     public void render() {
         // TODO Auto-generated method stub
         super.render();
         Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
         Gdx.gl.glClearColor(1, 1, 1, 1);

         rend.begin(ShapeType.Line);
         rend.setColor(Color.RED);
         for(int i=0; i<polygon1.getVertices().length; i+=2){
             rend.line(vertices1[i], vertices1[i+1], vertices1[(i+2)%vertices1.length], vertices1[(i+3)%vertices1.length]);
         }

         float[] vertices3 = polygon2.getVertices();
         for(int i=0; i<polygon2.getVertices().length; i+=2){
             rend.line(vertices3[i], vertices3[i+1], vertices3[(i+2)%vertices3.length], vertices3[(i+3)%vertices3.length]);
         }
         rend.end();

         //if(polygon1.contains(point.x, point.y)){
         if( isOverlap(polygon1, polygon2) ){
             rend.setColor(Color.RED);
         }else{
             rend.setColor(Color.BLUE);
         }
         rend.begin(ShapeType.Filled);
         rend.circle(point.x, point.y, 5);
         rend.end();

     }

     @Override
     public void dispose() {
         // TODO Auto-generated method stub
         super.dispose();
     }

 }

运行结果：

  

展示了三种情况，当然，这里只是进行简单的测试，可以任意绘制多边形进行检测。