JS/HTML5游戏开发：基于网格的碰撞检测算法详解

代码实现与测试

var mapArr = [
      1, 0, 0, 1,
      0, 0, 0, 1,
      0, 1, 0, 0,
      1, 0, 0, 1
    ];

<!DOCTYPE html>
<html lang="en">
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
  <meta charset="UTF-8">
  <title>地图格子算法</title>
  <style>
    #stage {
      border: 1px solid lightgray;
    }
  </style>
</head>
<body>
<canvas id="stage"></canvas>
</body>
<script>
  window.onload = function () {
    var stage = document.querySelector('#stage'),
      ctx = stage.getContext('2d');
    stage.width = 400;
    stage.height = 400;
    var mapArr = [
      1, 0, 0, 1,
      0, 0, 0, 1,
      0, 1, 0, 0,
      1, 0, 0, 1
    ],rectIdx = 5;
    //栅格线条
    function drawGrid(context, color, stepx, stepy) {
      context.strokeStyle = color;
      context.lineWidth = 0.5;
      for (var i = stepx + 0.5; i < context.canvas.width; i += stepx) {
        context.beginPath();
        context.moveTo(i, 0);
        context.lineTo(i, context.canvas.height);
        context.stroke();
      }
      for (var i = stepy + 0.5; i < context.canvas.height; i += stepy) {
        context.beginPath();
        context.moveTo(0, i);
        context.lineTo(context.canvas.width, i);
        context.stroke();
      }
    }
    function createRect(x, y, r, c) {
      ctx.beginPath();
      ctx.fillStyle = c;
      ctx.rect(x, y, r, r);
      ctx.fill();
    }
    document.onkeydown = function (event) {
      var e = event || window.event || arguments.callee.caller.arguments[0];
      //根据地图数组碰撞将测
      switch (e.keyCode){
        case 37:
          console.log("Left");
          if (rectIdx - 1 >= 0 && (rectIdx - 1) % 4 !== 3 && !mapArr[rectIdx - 1]) {
            rectIdx -= 1;
          }
          break;
        case 38:
          console.log("Top");
          if (rectIdx - 4 >= 0 && !mapArr[rectIdx - 4]) {
            rectIdx -= 4;
          }
          break;
        case 39:
          console.log("Right");
          if ((rectIdx + 1) % 4 !== 0 && !mapArr[rectIdx + 1]) {
            rectIdx += 1;
          }
          break;
        case 40:
          console.log("Bottom");
          if (rectIdx + 4 < mapArr.length && !mapArr[rectIdx + 4]) {
            rectIdx += 4;
          }
          break;
        default:
          return false;
　　　　　　 }
    };
    function update() {
      ctx.clearRect(0, 0, 400, 400);
      drawGrid(ctx, 'lightgray', 100, 100);
      var rect = {
        x: rectIdx % 4 * 100,
        y: rectIdx % 4 === 0 ? rectIdx / 4 * 100 : Math.floor(rectIdx / 4) * 100,
        r: 100,
        c: "blue"
      };
      createRect(rect.x, rect.y, rect.r, rect.c);
      //根据地图数组创建色块
      for (var i = 0, len = mapArr.length; i < len; i++) {
        if (mapArr[i]) {
          createRect(i % 4 * 100, i % 4 === 0 ? i / 4 * 100 : Math.floor(i / 4) * 100, 100, "red");
        }
      }
      requestAnimationFrame(update);
    }
    update();
  };
</script>
</html>