所以我正在使用画布制作这个节奏游戏，到目前为止所做的就是渲染接收器（块将要碰撞的点，这样用户可以按下相应的按钮并获得积分）它呈现舞者动画。出于某种原因，虽然在页面打开一段时间之后，舞者显着减慢并继续逐渐减慢。
我无法弄清楚为什么或如何解决它。有人有主意吗？
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 500;
canvas.height = 600;
document.body.appendChild(canvas);
var spritesheet = null;
var dancer = {
time:0,
speed:0,
image:null,
x:0,
y:0,
currentFrame:0,
width:50,
height:100,
ready:false
}
function onload() {
spritesheet = new Image();
spritesheet.src = "danceSheet.png";
spritesheet.onload = initiate;
}
function initiate() {
game.startTime = new Date().getTime() / 1000;
dancer.x = (canvas.width / 2) - dancer.width;
dancer.y = 120;
game.initiateReceivers();
main();
}
var game = {
startTime:0,
currentTime:0,
receivers:[],
senders:[],
lanes:[],
drawDancer: function() {
ctx.drawImage(spritesheet, dancer.width * dancer.currentFrame, 0, dancer.width, dancer.height, dancer.x, dancer.y, dancer.width, dancer.height );
},
clearWindow: function() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
},
initiateReceivers: function() {
var distanceRate = canvas.width / 4;
var position = 30;
for(initiates = 0; initiates < 4; initiates++) {
this.receivers[initiates] = new receivers;
this.receivers[initiates].x = position;
this.receivers[initiates].y = 300;
position += distanceRate;
}
}
}
var gameUpdates = {
updateMovement: function() {
game.currentTime = new Date().getTime() / 1000;
dancer.time = game.currentTime - game.startTime;
if(dancer.time >= 0.1) {
game.startTime = new Date().getTime() / 1000;
dancer.currentFrame += 1;
if(dancer.currentFrame == 12) dancer.currentFrame = 0;
}
},
collision: function(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);
// 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) {
return true;
}
return false;
}
}
function receivers() {
this.x = 0;
this.y = 0;
this.width = 60;
this.height = 10;
}
function senders() {
this.x = 0;
this.y = 0;
this.width = 60;
this.height = 10;
this.lane = 0;
this.status = true;
}
function update() {
gameUpdates.updateMovement();
}
function render() {
game.clearWindow();
game.drawDancer();
game.receivers.forEach( function(receiver) {
ctx.rect(receiver.x,receiver.y,receiver.width,receiver.height);
ctx.fillStyle = "red";
ctx.fill();
}
)
}
function main() {
update();
render();
requestAnimationFrame(main);
}
答案 0 :(得分：1)
我试图了解您所看到的缓慢程度，因此我调整了您的代码以获得每秒帧数。 Haven找不到原因。
<强>更新
我发现画框正在从绘制矩形中掉落。我已经改变了代码以使用fillRect将填充样式放在循环之外。这似乎修复了帧丢失。
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 500;
canvas.height = 600;
document.body.appendChild(canvas);
var spritesheet = null;
var dancer = {
time: 0,
speed: 0,
image: null,
x: 0,
y: 0,
currentFrame: 0,
width: 50,
height: 100,
ready: false
}
function onload() {
spritesheet = document.createElement('canvas');
spritesheet.width = (dancer.width * 12);
spritesheet.height = dancer.height;
var ctx = spritesheet.getContext('2d');
ctx.font = "30px Arial";
ctx.fillStyle = "black";
ctx.strokeStyle = "red";
for (var i = 0; i < 12; i++) {
var x = (i * dancer.width) + 10;
ctx.fillText(i,x,60);
ctx.beginPath();
ctx.rect(i*dancer.width,0,dancer.width,dancer.height);
ctx.stroke();
}
initiate();
}
function initiate() {
game.startTime = new Date().getTime() / 1000;
dancer.x = (canvas.width / 2) - dancer.width;
dancer.y = 120;
game.initiateReceivers();
main();
}
var game = {
startTime: 0,
currentTime: 0,
receivers: [],
senders: [],
lanes: [],
drawDancer: function() {
ctx.drawImage(spritesheet, dancer.width * dancer.currentFrame, 0, dancer.width, dancer.height, dancer.x, dancer.y, dancer.width, dancer.height);
//ctx.strokeStyle="red";
//ctx.beginPath();
//ctx.lineWidth = 3;
//ctx.rect(dancer.x,dancer.y,dancer.width,dancer.height);
//ctx.stroke();
},
clearWindow: function() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
},
initiateReceivers: function() {
var distanceRate = canvas.width / 4;
var position = 30;
for (initiates = 0; initiates < 4; initiates++) {
this.receivers[initiates] = new receivers;
this.receivers[initiates].x = position;
this.receivers[initiates].y = 300;
position += distanceRate;
}
}
};
var gameUpdates = {
updateMovement: function() {
game.currentTime = new Date().getTime() / 1000;
dancer.time = game.currentTime - game.startTime;
if (dancer.time >= 0.1) {
game.startTime = new Date().getTime() / 1000;
dancer.currentFrame += 1;
if (dancer.currentFrame == 12) dancer.currentFrame = 0;
}
},
collision: function(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);
// 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) {
return true;
}
return false;
}
}
function receivers() {
this.x = 0;
this.y = 0;
this.width = 60;
this.height = 10;
}
function senders() {
this.x = 0;
this.y = 0;
this.width = 60;
this.height = 10;
this.lane = 0;
this.status = true;
}
function update() {
gameUpdates.updateMovement();
}
function render() {
game.clearWindow();
game.drawDancer();
ctx.fillStyle = "red";
game.receivers.forEach(function(receiver) {
ctx.fillRect(receiver.x, receiver.y, receiver.width, receiver.height);
});
ctx.fillText(fps,10,10);
}
var fps = 0;
var frames = 0;
function getFps() {
fps = frames;
frames = 0;
setTimeout(getFps,1000);
}
getFps();
function main() {
update();
render();
frames++;
requestAnimationFrame(main);
}
onload();canvas {
border:1px solid blue;
}