我正在尝试使我的云可拖动。它有效，但从我的示例中可以看出，云总是从中心剪切到鼠标位置。
这是我当前的设置。
$(document).ready(function () {
var canvas = document.getElementById("background-canvas");
canvas.width = $(window).width();
canvas.height = $(window).height();
canvas.style.zIndex = -1;
var ctx = canvas.getContext("2d");
var mousePosition = new Vector2d(0,0);
var background = new Background(ctx, canvas.width, canvas.height, new Color(224,247,250,0.8));
var cloud = new Cloud(background, 300, 100, new Vector2d(10,10), 20, 1000);
img=new Image();
img.src="https://i.imgur.com/hIVsoho.png";
background.addCloud(cloud);
for (var i = 0; i < background.allClouds.length; i++){
var selectedCloud = background.allClouds[i];
for (var j = 0; j < selectedCloud.maxNumberofPixels; j++){
var pixel = cloud.createPixel(); // TODO: cloud shall not define pixel.
//new Pixel(2, 4, getRandomLocationWithinParent(selectedCloud), new Vector2d(0,5), new Vector2d(0,0), new Color(0,0,128,1));
cloud.addPixel(pixel);
}
}
/*
* Input listeners
*/
document.addEventListener("mousemove", function (evt) {
mousePosition = getMousePos(canvas, evt);
}, false);
document.addEventListener("mousedown", function (evt){
console.log(mousePosition);
for(var i = 0; i < background.allClouds.length; i++)
if(background.allClouds[i].hover(mousePosition))
background.allClouds[i].isClicked = true;
}, false)
document.addEventListener("mouseup", function (evt){
for(var i = 0; i < background.allClouds.length; i++)
if(background.allClouds[i].hover(mousePosition))
background.allClouds[i].isClicked = false;
}, false)
setInterval(updateBackground, 20);
function updateBackground() {
// paint background color.
ctx.fillStyle = background.color.getColorString();
ctx.fillRect(0,0,background.width, background.height);
// paint clouds
for(var i = 0; i < background.allClouds.length; i++){
var selectedCloud = background.allClouds[i];
//ctx.fillStyle = selectedCloud.color.getColorString();
//ctx.fillRect(0, 0, selectedCloud.width, selectedCloud.height); rectangle view of cloud.
// paint rain
var deadPixelContainer = [];
for (var j = 0; j < selectedCloud.allPixels.length; j++){
var selectedPixel = selectedCloud.allPixels[j];
ctx.fillStyle = selectedPixel.color.getColorString();
ctx.save();
ctx.translate(selectedPixel.location.x, selectedPixel.location.y);
ctx.fillRect(-selectedPixel.width / 2, -selectedPixel.height / 2, selectedPixel.width, selectedPixel.height);
ctx.restore();
if(!selectedPixel.alive){
deadPixelContainer.push(selectedPixel);
continue;
}
selectedPixel.update();
selectedPixel.checkEdges(background);
}
if(deadPixelContainer.length > 0){
selectedCloud.removePixels(deadPixelContainer);
}
ctx.save();
ctx.translate(selectedCloud.location.x, selectedCloud.location.y);
ctx.drawImage(img,0,0,img.width,img.height,-25, -10,350,100);
ctx.restore();
cloud.update(mousePosition);
}
}
// TODO: Create object for mouse
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return new Vector2d(evt.clientX - rect.left, evt.clientY - rect.top);
}
});
function Cloud(background, width, height, location, startNumberOfPixels, maxNumberofPixels){
this.width = width;
this.height = height;
this.location = location;
this.allPixels = [];
this.maxNumberofPixels = maxNumberofPixels;
this.color = new Color(255,255,255,0.5);
this.isClicked = false;
this.rainStrength = 5; // how often cloud spawns new pixels per update cycle.
this.addPixel = function(pixel){
if(this.allPixels.length <= startNumberOfPixels)
this.allPixels.push(pixel);
}
this.update = function(mousePosition){
// make cloud draggable
if(this.isClicked){
var offsetX = mousePosition.x - this.location.x;
var offsetY = mousePosition.y - this.location.y;
this.location = new Vector2d(this.location.x + offsetX - this.width/2, this.location.y + offsetY - this.height/2);
}
// add more pixels overtime.
if(this.allPixels.length <= this.maxNumberofPixels)
for(var i = 0; i < this.rainStrength; i++)
this.allPixels.push(this.createPixel());
}
this.hover = function(mousePosition){
if(mousePosition.x > this.location.x
&& mousePosition.x < this.location.x + this.width
&& mousePosition.y > this.location.y
&& mousePosition.y < this.location.y + this.height)
return true;
return false;
}
this.createPixel = function(){
return new Pixel(2, 4, this.getRandomLocation(), new Vector2d(0,7), new Vector2d(0,0.05), new Color(0,0,128,1));
}
this.removePixels = function(deadPixelContainer){
for(var i = 0; i < deadPixelContainer.length; i++){
try{
var pixelContainer = this.allPixels.slice();
pixelContainer.splice(this.allPixels.findIndex(v => v === deadPixelContainer[i]), 1).slice();
this.allPixels = pixelContainer.slice();
}catch(e){
console.log(e);
}
}
}
this.getRandomLocation = function(){
var minWidth = this.location.x;
var maxWidth = this.location.x + this.width;
var minHeight = this.location.y + this.height/2; // don't count upper part of cloud. Rain forms at the bottom.
var maxHeight = this.location.y + this.height;
var randomWidthLocation = Math.random() * (maxWidth - minWidth + 1)+minWidth;
var randomHeightLocation = Math.random() * (maxHeight - minHeight + 1) + minHeight;
return new Vector2d(randomWidthLocation, randomHeightLocation);
}
}
function Background(ctx, width, height, color){
this.width = width;
this.height = height;
this.color = color; //"#191919"
this.isPaused = false;
this.allPixels = []; // might need to be removed.
this.allClouds = [];
this.pixelCount = 150;
this.addCloud = function(cloud){
this.allClouds.push(cloud);
};
this.refreshCanvas = function(){
this.width = $(window).width();
this.height = $(window).height();
};
this.addPixelOn = function(pixelWidht, pixelHeight, location, velocity, acceleration, color) { // might need to be removed.
var pixel = new Pixel(pixelWidht, pixelHeight, location, velocity, acceleration, color);
this.allPixels.push(pixel);
};
this.addPixel = function(pixelWidht, pixelHeight, velocity, acceleration, color) { // might need to be removed.
var location = new Vector2d(Math.random() * this.width, Math.random() * this.height);
this.addPixelOn(pixelWidht, pixelHeight, location, velocity, acceleration, color);
};
}
function Pixel(widht, height, location, velocity, acceleration, color) {
this.height = height;
this.width = widht;
this.color = color; //"#00CC33"
this.location = location;
this.velocity = velocity;
this.acceleration = acceleration;
this.alive = true;
this.update = function () {
this.velocity.add(this.acceleration);
//this.velocity.limit(topspeed);
this.location.add(this.velocity);
};
this.checkEdges = function (background) {
if (this.location.y > background.height) {
this.alive = false;
}
};
this.setColor = function(color){
this.color = color;
};
this.setHeight = function(height){
this.height = height;
};
this.setWidth = function(width){
this.width = width;
}
}
function Color(r,g,b,o){
this.red = r;
this.green = g;
this.blue = b;
this.opacity = o;
this.getColorString = function(){
return "rgba("+this.red+","+this.green+","+this.blue+","+this.opacity+")";
}
}
function Vector2d(x, y) {
this.x = x;
this.y = y;
this.add = function (vector2d) {
this.x += vector2d.x;
this.y += vector2d.y;
};
this.sub = function (vector2d) {
this.x -= vector2d.x;
this.y -= vector2d.y;
};
this.mult = function (mult) {
this.x *= mult;
this.y *= mult;
};
this.div = function (div) {
this.x /= div;
this.y /= div;
};
this.mag = function () {
return Math.sqrt(this.x * this.x, this.y * this.y);
};
this.norm = function () {
var m = this.mag();
if (m !== 0) {
this.div(m);
}
}
}#background-canvas {
position: fixed;
width: 100%;
height: 100%
background-color:red;
top:0;
left:0;
}<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>
<canvas id="background-canvas" />
</body>
</html>设置拖动时云的位置的代码是这样的:
// make cloud draggable
if(this.isClicked){
var offsetX = mousePosition.x - this.location.x;
var offsetY = mousePosition.y - this.location.y;
this.location = new Vector2d(this.location.x + offsetX - this.width/2, this.location.y + offsetY - this.height/2);
}
这不能正常工作。我希望它不要夹到中心。
谁能帮我解决这个问题吗？
如果不完全清楚问题是什么或者您需要任何额外信息，请询问。
最佳答案
您需要记住云本地坐标系中的点击位置:
if(background.allClouds[i].hover(mousePosition)) {
background.allClouds[i].isClicked = true;
background.allClouds[i].clickLocalPosition = new Vector2d(mousePosition.x, mousePosition.y);
background.allClouds[i].clickLocalPosition.sub(background.allClouds[i].location);
}
然后，当您更新时，您将根据点击位置计算新位置:
this.location.x = mousePosition.x - this.clickLocalPosition.x;
this.location.y = mousePosition.y - this.clickLocalPosition.y;
$(document).ready(function () {
var canvas = document.getElementById("background-canvas");
canvas.width = $(window).width();
canvas.height = $(window).height();
canvas.style.zIndex = -1;
var ctx = canvas.getContext("2d");
var mousePosition = new Vector2d(0,0);
var background = new Background(ctx, canvas.width, canvas.height, new Color(224,247,250,0.8));
var cloud = new Cloud(background, 300, 100, new Vector2d(10,10), 20, 1000);
img=new Image();
img.src="https://i.imgur.com/hIVsoho.png";
background.addCloud(cloud);
for (var i = 0; i < background.allClouds.length; i++){
var selectedCloud = background.allClouds[i];
for (var j = 0; j < selectedCloud.maxNumberofPixels; j++){
var pixel = cloud.createPixel(); // TODO: cloud shall not define pixel.
//new Pixel(2, 4, getRandomLocationWithinParent(selectedCloud), new Vector2d(0,5), new Vector2d(0,0), new Color(0,0,128,1));
cloud.addPixel(pixel);
}
}
/*
* Input listeners
*/
document.addEventListener("mousemove", function (evt) {
mousePosition = getMousePos(canvas, evt);
}, false);
document.addEventListener("mousedown", function (evt){
console.log(mousePosition);
for(var i = 0; i < background.allClouds.length; i++)
if(background.allClouds[i].hover(mousePosition)) {
background.allClouds[i].isClicked = true;
background.allClouds[i].clickLocalPosition = new Vector2d(mousePosition.x, mousePosition.y);
background.allClouds[i].clickLocalPosition.sub(background.allClouds[i].location);
}
}, false)
document.addEventListener("mouseup", function (evt){
for(var i = 0; i < background.allClouds.length; i++)
if(background.allClouds[i].hover(mousePosition))
background.allClouds[i].isClicked = false;
}, false)
setInterval(updateBackground, 20);
function updateBackground() {
// paint background color.
ctx.fillStyle = background.color.getColorString();
ctx.fillRect(0,0,background.width, background.height);
// paint clouds
for(var i = 0; i < background.allClouds.length; i++){
var selectedCloud = background.allClouds[i];
//ctx.fillStyle = selectedCloud.color.getColorString();
//ctx.fillRect(0, 0, selectedCloud.width, selectedCloud.height); rectangle view of cloud.
// paint rain
var deadPixelContainer = [];
for (var j = 0; j < selectedCloud.allPixels.length; j++){
var selectedPixel = selectedCloud.allPixels[j];
ctx.fillStyle = selectedPixel.color.getColorString();
ctx.save();
ctx.translate(selectedPixel.location.x, selectedPixel.location.y);
ctx.fillRect(-selectedPixel.width / 2, -selectedPixel.height / 2, selectedPixel.width, selectedPixel.height);
ctx.restore();
if(!selectedPixel.alive){
deadPixelContainer.push(selectedPixel);
continue;
}
selectedPixel.update();
selectedPixel.checkEdges(background);
}
if(deadPixelContainer.length > 0){
selectedCloud.removePixels(deadPixelContainer);
}
ctx.save();
ctx.translate(selectedCloud.location.x, selectedCloud.location.y);
ctx.drawImage(img,0,0,img.width,img.height,-25, -10,350,100);
ctx.restore();
cloud.update(mousePosition);
}
}
// TODO: Create object for mouse
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return new Vector2d(evt.clientX - rect.left, evt.clientY - rect.top);
}
});
function Cloud(background, width, height, location, startNumberOfPixels, maxNumberofPixels){
this.width = width;
this.height = height;
this.location = location;
this.allPixels = [];
this.maxNumberofPixels = maxNumberofPixels;
this.color = new Color(255,255,255,0.5);
this.isClicked = false;
this.rainStrength = 5; // how often cloud spawns new pixels per update cycle.
this.addPixel = function(pixel){
if(this.allPixels.length <= startNumberOfPixels)
this.allPixels.push(pixel);
}
this.update = function(mousePosition){
// make cloud draggable
if(this.isClicked){
this.location.x = mousePosition.x - this.clickLocalPosition.x;
this.location.y = mousePosition.y - this.clickLocalPosition.y;
}
// add more pixels overtime.
if(this.allPixels.length <= this.maxNumberofPixels)
for(var i = 0; i < this.rainStrength; i++)
this.allPixels.push(this.createPixel());
}
this.hover = function(mousePosition){
if(mousePosition.x > this.location.x
&& mousePosition.x < this.location.x + this.width
&& mousePosition.y > this.location.y
&& mousePosition.y < this.location.y + this.height)
return true;
return false;
}
this.createPixel = function(){
return new Pixel(2, 4, this.getRandomLocation(), new Vector2d(0,7), new Vector2d(0,0.05), new Color(0,0,128,1));
}
this.removePixels = function(deadPixelContainer){
for(var i = 0; i < deadPixelContainer.length; i++){
try{
var pixelContainer = this.allPixels.slice();
pixelContainer.splice(this.allPixels.findIndex(v => v === deadPixelContainer[i]), 1).slice();
this.allPixels = pixelContainer.slice();
}catch(e){
console.log(e);
}
}
}
this.getRandomLocation = function(){
var minWidth = this.location.x;
var maxWidth = this.location.x + this.width;
var minHeight = this.location.y + this.height/2; // don't count upper part of cloud. Rain forms at the bottom.
var maxHeight = this.location.y + this.height;
var randomWidthLocation = Math.random() * (maxWidth - minWidth + 1)+minWidth;
var randomHeightLocation = Math.random() * (maxHeight - minHeight + 1) + minHeight;
return new Vector2d(randomWidthLocation, randomHeightLocation);
}
}
function Background(ctx, width, height, color){
this.width = width;
this.height = height;
this.color = color; //"#191919"
this.isPaused = false;
this.allPixels = []; // might need to be removed.
this.allClouds = [];
this.pixelCount = 150;
this.addCloud = function(cloud){
this.allClouds.push(cloud);
};
this.refreshCanvas = function(){
this.width = $(window).width();
this.height = $(window).height();
};
this.addPixelOn = function(pixelWidht, pixelHeight, location, velocity, acceleration, color) { // might need to be removed.
var pixel = new Pixel(pixelWidht, pixelHeight, location, velocity, acceleration, color);
this.allPixels.push(pixel);
};
this.addPixel = function(pixelWidht, pixelHeight, velocity, acceleration, color) { // might need to be removed.
var location = new Vector2d(Math.random() * this.width, Math.random() * this.height);
this.addPixelOn(pixelWidht, pixelHeight, location, velocity, acceleration, color);
};
}
function Pixel(widht, height, location, velocity, acceleration, color) {
this.height = height;
this.width = widht;
this.color = color; //"#00CC33"
this.location = location;
this.velocity = velocity;
this.acceleration = acceleration;
this.alive = true;
this.update = function () {
this.velocity.add(this.acceleration);
//this.velocity.limit(topspeed);
this.location.add(this.velocity);
};
this.checkEdges = function (background) {
if (this.location.y > background.height) {
this.alive = false;
}
};
this.setColor = function(color){
this.color = color;
};
this.setHeight = function(height){
this.height = height;
};
this.setWidth = function(width){
this.width = width;
}
}
function Color(r,g,b,o){
this.red = r;
this.green = g;
this.blue = b;
this.opacity = o;
this.getColorString = function(){
return "rgba("+this.red+","+this.green+","+this.blue+","+this.opacity+")";
}
}
function Vector2d(x, y) {
this.x = x;
this.y = y;
this.add = function (vector2d) {
this.x += vector2d.x;
this.y += vector2d.y;
};
this.sub = function (vector2d) {
this.x -= vector2d.x;
this.y -= vector2d.y;
};
this.mult = function (mult) {
this.x *= mult;
this.y *= mult;
};
this.div = function (div) {
this.x /= div;
this.y /= div;
};
this.mag = function () {
return Math.sqrt(this.x * this.x, this.y * this.y);
};
this.norm = function () {
var m = this.mag();
if (m !== 0) {
this.div(m);
}
}
}#background-canvas {
position: fixed;
width: 100%;
height: 100%
background-color:red;
top:0;
left:0;
}<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>
<canvas id="background-canvas" />
</body>
</html>关于javascript - 为了获得更好的阻力效果，正确的偏移量是多少？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53379393/