Javascript Canvas 游戏 - 碰撞检测答案

【问题标题】：Javascript Canvas Game - Collision DetectionJavascript Canvas 游戏 - 碰撞检测
【发布时间】：2016-03-22 21:12:54
【问题描述】：

我正在构建一个小型迷你瓷砖引擎游戏。我目前正在实施简单的基于块的碰撞检测，但是我遇到了真正的问题。我已经用谷歌搜索了几个小时来查看不同的实现，但似乎无法理解它。我目前的努力（目前仅在玩家向右移动时检测到碰撞）大部分都有效，但允许玩家通过障碍物的底部。碰撞使用法线贴图数组来检测碰撞，贴图中任何值为 2 的都是实体对象。

我了解我需要做什么的概念 - 在我移动我的播放器之前，计算播放器最终将进入哪个单元格。检查已分配给该单元格的值。如果是 2，则不允许玩家移动。

我的问题是弄清楚玩家最终会进入哪个牢房，从技术上讲，玩家可以同时在 4 个牢房中。我已经尝试使用原点和 4 角检测来解决这个问题，但我无法让它工作。

这里的 JS 小提琴 - https://jsfiddle.net/j1xqxze8/

我的代码；

    var Player = function() {
        this.width = 16;
        this.height = 16;
        this.position   = {};
        this.position.x = 32;
        this.position.y = 32;
        this.speed      = 8;

        this.render = function() {
            window.context.fillStyle = 'white';
            window.context.fillRect(this.position.x, this.position.y, this.width, this.height);
        };

        var _self = this;

        this.didCollide = function(dir) {
            if(dir == 'right'){
                var newBlock = window.tileMap.getCell(Math.floor((_self.position.x + _self.width) / 32), Math.floor((this.position.y + this.height / 2) / 32));

                if(newBlock == 2)
                    return true;
            }
        };

        window.addEventListener('keydown', function(e) {
            if(e.keyCode == 38 || e.keyCode == 87){
                _self.position.y -= _self.speed;
            }

            if(e.keyCode == 40 || e.keyCode == 83){
                _self.position.y += _self.speed;
            }

            if(e.keyCode == 37 || e.keyCode == 65){
                _self.position.x -= _self.speed;
            }

            if(e.keyCode == 39 || e.keyCode == 68){
                if(!_self.didCollide('right')){
                    _self.position.x += _self.speed;
                }
            }
        })
    };

var TileMap = function() {
    this.map = [
        [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 2, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
        [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
    ];

    this.tileSize = 32;
    this.colors = ['black', 'red', 'green'];

    this.getCell = function(x, y){
      return this.map[y][x];
    };

        this.render = function(){
            for(var x = 0; x < this.map.length; x++){
                for(var y = 0; y < this.map.length; y++){
                    // SWAP Y AND X IN THE FILLSTYLE DUE TO BACKWARDS/MIRRORED JS ARRAY READING
                    window.context.fillStyle = this.colors[this.map[y][x]];
                    window.context.fillRect((x * this.tileSize) - window.camera.position.x, (y * this.tileSize) - window.camera.position.y, this.tileSize, this.tileSize);

                    window.context.strokeStyle = 'yellow';
                    window.context.strokeRect((x * this.tileSize) - window.camera.position.x, (y * this.tileSize) - window.camera.position.y, this.tileSize, this.tileSize);
                }
            }
        }
    };

【问题讨论】：

由于每次 keydown 移动播放器 8 个位置，在 keydown 中您必须测试这 8 个位置中的每一个以查看是否发生碰撞。
我已经尝试过不同程度的速度，包括1（以便只更新一次位置），即使在这个级别，问题仍然存在，您可以深入夹入对象- 不过谢谢 :)
我添加了一个（粗略的、未经测试的）答案，展示了如何测试每个中间位置以查看是否发生碰撞。

标签： javascript html canvas collision-detection

【解决方案1】：

您需要通过在当前 x/y 位置上加/减速度来计算玩家的新位置。然后你需要计算玩家在新位置所覆盖的像素范围。然后您需要计算与像素范围相对应的单元格范围。然后您需要遍历单元格范围以查看是否有任何冲突。注意，计算玩家覆盖的右/下像素时，需要将x/y和width/height相加再减1。

改变...

this.didCollide = function(dir) {
    if(dir == 'right'){
        var newBlock = window.tileMap.getCell(Math.floor((_self.position.x + _self.width) / 32), Math.floor((this.position.y + this.height / 2) / 32));
        if(newBlock == 2)
            return true;
    }
};

到...

this.didCollide = function(dir) {
    if(dir == 'right'){
        var col1 = Math.floor((_self.position.x + _self.speed) / 32);
        var col2 = Math.floor((_self.position.x + _self.speed + _self.width - 1) / 32);
        var row1 = Math.floor((_self.position.y) / 32);
        var row2 = Math.floor((_self.position.y + _self.height - 1) / 32);
        document.getElementById("player").textContent = "player: " + _self.position.x + " " + _self.position.y + " " + _self.width + " " + _self.height;
        document.getElementById("cells").textContent = "cells: " + col1 + " " + col2 + " " + row1 + " " + row2;
        for (var c = col1; c <= col2; c++) {
            for (var r = row1; r <= row2; r++) {
                var newBlock = window.tileMap.getCell(c, r);
                if(newBlock == 2) {
                    return true;
                }
            }
        }
    }
    return false;
};

【讨论】：

【解决方案2】：

由于每次 keydown 将播放器移动 8 个位置，因此在 keydown 中，您必须测试这 8 个中间位置中的每一个以查看是否发生碰撞。

警告：未经测试的代码——需要一些调整（可能！）

window.addEventListener('keydown', function(e) {
    // save x,y before the move
    var beginningX=_self.position.x;
    var beginningY=_self.position.y;

    // test each interim positon between the beginning & 
    // current position for collisions
    // if a collision occurs, stop at the collision position
    if(e.keyCode == 38 || e.keyCode == 87){
        _self.position.y -= _self.speed;
        _self.position.y = testInterimVerticalCollisions(
            beginningY, _self.position.y, _self.position.x);
    }

    if(e.keyCode == 40 || e.keyCode == 83){
        _self.position.y += _self.speed;
        _self.position.y = testInterimVerticalCollisions(
            beginningY, _self.position.y, _self.position.x);
    }

    if(e.keyCode == 37 || e.keyCode == 65){
        _self.position.x -= _self.speed;
        _self.position.x = testInterimHorizontalCollisions(
            beginningX, _self.position.x, _self.position.y);
    }

    if(e.keyCode == 39 || e.keyCode == 68){
        _self.position.x += _self.speed;
        _self.position.x = testInterimHorizontalCollisions(
            beginningX, _self.position.x, _self.position.y);
        }
    }
})

// test if any interim movement caused a collision
// if yes, return the x that caused the collision
// if no, return the ending x
function testInterimHorizontalCollisions(beginningX,endingX,y){
    for(var x=beginningX;x<=endingX;x++){
        // TODO: adjust for camera position offset
        var cellX = parseInt(x/cellWidth);
        var cellY = parseInt(y/cellHeight);
        if(getCell(cellX,cellY)==2){return(x);}
    }
    return(endingX);
}

// test if any interim movement caused a collision
// if yes, return the y that caused the collision
// if no, return the ending y
function testInterimVerticalCollisions(beginningY,endingY,x){
    for(var y=beginningY;y<=endingY;y++){
        // TODO: adjust for camera position offset
        var cellX = parseInt(x/cellWidth);
        var cellY = parseInt(y/cellHeight);
        if(getCell(cellX,cellY)==2){return(y);}
    }
    return(endingY);
}

【讨论】：

谢谢！我最终选择了基于此答案的解决方案。总有一天，这一切对我来说都很容易，但还不是；）