javascript - 2D 平台游戏，在 html5 中制作玩家相机 View

Question

我想修改我在 codepen 中找到的平台游戏。 http://codepen.io/loktar00/pen/JEdqD原图如下图。

我想把它改成:

我想放大播放器的视口(viewport)并制作一个类似相机的 View ，我可以在其中滚动 Canvas 元素中的一个级别。

喜欢这个游戏http://www.html5quintus.com/quintus/examples/platformer_full/

视口(viewport)和相机正在跟踪玩家。

这是我的代码:

(function () {
    var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
    window.requestAnimationFrame = requestAnimationFrame;
})();

var canvas = document.getElementById("canvas"),
    ctx = canvas.getContext("2d"),
    width = 100,
    height = 100,
    player = {
        x: width / 2,
        y: height - 15,
        width: 5,
        height: 5,
        speed: 3,
        velX: 0,
        velY: 0,
        jumping: false,
        grounded: false
    },
    keys = [],
    friction = 0.8,
    gravity = 0.3;

var boxes = [];

// player's position
var playerX = 20;
var playerY = 20;

// how far offset the canvas is
var offsetX = 0;
var offsetY = 0;

// dimensions
boxes.push({
    x: 0,
    y: 0,
    width: 10,
    height: height
});
boxes.push({
    x: 0,
    y: height - 2,
    width: width,
    height: 50
});
boxes.push({
    x: width - 10,
    y: 0,
    width: 50,
    height: height
});

boxes.push({
    x: 120,
    y: 10,
    width: 80,
    height: 80
});
boxes.push({
    x: 170,
    y: 50,
    width: 80,
    height: 80
});
boxes.push({
    x: 220,
    y: 100,
    width: 80,
    height: 80
});
boxes.push({
    x: 270,
    y: 150,
    width: 40,
    height: 40
});

canvas.width = width;
canvas.height = height;

function update() {
    // check keys
    if (keys[38] || keys[32] || keys[87]) {
        // up arrow or space
        if (!player.jumping && player.grounded) {
            player.jumping = true;
            player.grounded = false;
            player.velY = -player.speed * 2;
        }
    }
    if (keys[39] || keys[68]) {
        // right arrow
        if (player.velX < player.speed) {
            player.velX++;
             offsetX--;
        }
    }
    if (keys[37] || keys[65]) {
        // left arrow
        if (player.velX > -player.speed) {
            player.velX--;
             offsetX++;
        }
    }

    player.velX *= friction;
    player.velY += gravity;

    ctx.clearRect(0, 0, width, height);
    ctx.fillStyle = "black";
    ctx.beginPath();
    
    player.grounded = false;
    for (var i = 0; i < boxes.length; i++) {
        ctx.rect(boxes[i].x, boxes[i].y, boxes[i].width, boxes[i].height);
        
        var dir = colCheck(player, boxes[i]);

        if (dir === "l" || dir === "r") {
            player.velX = 0;
            player.jumping = false;
        } else if (dir === "b") {
            player.grounded = true;
            player.jumping = false;
        } else if (dir === "t") {
            player.velY *= -1;
        }

    }
    
    if(player.grounded){
         player.velY = 0;
    }
    
    player.x += player.velX;
    player.y += player.velY;

    ctx.save();
    ctx.translate(offsetX, offsetY);
    // clear the viewport
    ctx.clearRect(-offsetX, -offsetY, 100,100);

    ctx.fill();
    ctx.fillStyle = "red";
    ctx.fillRect(player.x, player.y, player.width, player.height);

     ctx.fillRect(playerX-offsetX, playerY-offsetY, 8, 8);
    
    // draw the other stuff
    var l = boxes.length;
    for (var i = 0; i < l; i++) {
        // we should really only draw the things that intersect the viewport!
        // but I am lazy so we are drawing everything here
        var x = boxes[i][0];
        var y = boxes[i][1];
        ctx.fillStyle = 'lightblue';
        ctx.fillRect(x, y, 8, 8);
        ctx.fillStyle = 'black';
        ctx.fillText(x + ', ' + y, x, y) // just to show where we are drawing these things
    }
    
    ctx.restore();
       
    requestAnimationFrame(update);
}

function colCheck(shapeA, shapeB) {
    // get the vectors to check against
    var vX = (shapeA.x + (shapeA.width / 2)) - (shapeB.x + (shapeB.width / 2)),
        vY = (shapeA.y + (shapeA.height / 2)) - (shapeB.y + (shapeB.height / 2)),
        // add the half widths and half heights of the objects
        hWidths = (shapeA.width / 2) + (shapeB.width / 2),
        hHeights = (shapeA.height / 2) + (shapeB.height / 2),
        colDir = null;

    // if the x and y vector are less than the half width or half height, they we must be inside the object, causing a collision
    if (Math.abs(vX) < hWidths && Math.abs(vY) < hHeights) {
        // figures out on which side we are colliding (top, bottom, left, or right)
        var oX = hWidths - Math.abs(vX),
            oY = hHeights - Math.abs(vY);
        if (oX >= oY) {
            if (vY > 0) {
                colDir = "t";
                shapeA.y += oY;
            } else {
                colDir = "b";
                shapeA.y -= oY;
            }
        } else {
            if (vX > 0) {
                colDir = "l";
                shapeA.x += oX;
            } else {
                colDir = "r";
                shapeA.x -= oX;
            }
        }
    }
    return colDir;
}

document.body.addEventListener("keydown", function (e) {
    keys[e.keyCode] = true;
});

document.body.addEventListener("keyup", function (e) {
    keys[e.keyCode] = false;
});


window.addEventListener("load", function () {
    update();
});

 <h3>A, D or Arrow keys to move, W or space to jump</h3>
    <canvas id="canvas"></canvas>

但这行不通。

Answer 1

您可以使用代码笔中的相同代码，但在第一个 update() 之前的 load 事件中添加几行。

让我们这样说:

window.addEventListener("load", function () {
    ctx.scale(2,2);
    ctx.translate(-100,-100);
    update();
});

这将放大两倍并以新坐标为中心，但是请记住，如果您想在玩家离开 View 时重新居中，则必须自己做。

作为执行此操作的部分方法，您可以使用 player.velX 和 player.velY 的相反值检查玩家是否移动和平移 Canvas 。像这样的东西:

var playerMoved = false;

if (keys[38] || keys[32] || keys[87]) {
    playerMoved = true;
    //...Other stuff
}

if (keys[39] || keys[68]) {
    playerMoved = true;
    //...Other stuff
}

if (keys[37] || keys[65]) {
    playerMoved = true;
    //...Other stuff
}

if (playerMoved) {
    // You still need to check quite a few things, like
    // the player being out of bounds, the view not translating
    // when x less than or bigger then a specific value, and so on
    ctx.translate(-player.velX, -player.velY);
}

这不是一个完整的解决方案，因为它需要相当多的代码，但它应该能让您入门。