旋转精灵Javascript [英] Rotate sprite javascript
问题描述
我有一个精灵动画,一个使用3D应用程序渲染的小炮.我在360度转弯时有360帧.每张图片的像素均为100x100.
I have a sprite animation, a small cannon rendered using a 3D app. I have exactly 360 frames for a 360 degree turn. Each image has a 100x100 pixel size.
所以基本上我想做的是,当我单击页面中的任何地方时,大炮的枪管需要旋转以指向鼠标光标,听起来很简单,但我真的无法使其正常工作,也许是因为我缺乏数学技能:P
So basically what I am trying todo is when I click anywhere in the page, the barrel of the cannon needs to rotate to point at the mouse cursor, sound simple maybe but I can't really get it to work very well, perhaps cause my math skills is lacking :P
我目前拥有的是这样的东西
What I currently have is something like this
/* This is my div with the cannon background image (360 images stitched into one) each "image area" is 100x100px */
obj.cannon = $('#cannon');
/* Get the X/Y of the cannon loc in the dom */
var cannonX = $(obj.cannon).offset().left;
var cannonY = $(obj.cannon).offset().top;
/* Get radians using atan2 */
var radians = Math.atan2(e.pageY-cannonY, e.pageX-cannonX);
/* Convert to degrees */
var degrees = radians * (180/Math.PI);
这就是我的意思,因为图像宽度为100px,并且我需要将背景位置移动100px才能将加农炮向右移动1度,因为总共有360张图像* 100px = 36000px.因此,拼接后的Sprite宽度约为36000px.
And this is where I am, I mean since the image width is 100px and I need to move the background-position by 100px to move the cannon one degree right, because 360 images * 100px = 36000px in total. So the stitched sprite is like 36000px wide.
所以
在此基于图像精灵的当前backgroundPosition插入怪异的计算,并根据您用鼠标光标单击的位置应用新的backgroundPosition,然后使用某种setTimeout(animateIt,speed);将背景位置动画化"到新位置.
Insert weird calculation here based on the current backgroundPosition of the image-sprite and apply new backgroundPosition based on where you click with the mouse cursor, then use some sort of setTimeout(animateIt, speed); to "animate" the background position to the new position.
function animateIt(){
if(newpos!=targetpos) { //Use < > here if we need to add or remove
newpos+=100; //Until we arrive at the new backgroundPosition
$(obj.cannon).css({backgroundPosition: newpos+'px' });
setTimeout(animateIt, speed);
}
}
我在这里是否完全正确,我是否在正确考虑?我觉得很愚蠢,这应该是一件简单的事情,但是现在我的大脑崩溃了,我认为= P.我的问题是我不知道如何正确到达新目标背景位置",然后根据当前背景位置对其进行++或-动画处理:/
Am I at all on the right track here, am I thinking correctly about this? I feel stupid, this should be a simple thing but right now I am having a brain meltdown I think =P. My problem is I don't know how to properly arrive at the "new target backgroundposition" and then animate it ++ or -- based on the current background position :/
推荐答案
这是一个包含10张图像的简化工作示例.
Well, here is a simplified working example with 10 images.
我现在将发布代码并 jsFiddle ,我可能会稍后再回来进行深入介绍.但基本上,您只是正确地订购了图像,然后使用(Segments - Math.floor(degree / (360 / segments)))
来选择细分.您可能需要调整您的0
度.例如,我使0
等于90
的正常水平.
I'll post the code and jsFiddle now, and I might come back later to cover it in depth. But basically you just order your images correctly, and then you pick the segment by using (Segments - Math.floor(degree / (360 / segments)))
. You may have to adjust your 0
degree. For example, I made my 0
equal to what would normal by 90
.
请注意以下事实:屏幕坐标x和y向右增加并向下.这使得atan
的度数是顺时针工作的,而不是x和y分别向右和上递增的坐标系中通常的逆时针方向.
Pay attention to the fact that the screen coordinates, x and y, increase right and down. This makes the degrees of atan
work clockwise instead of the usual counter clockwise in coordinate systems where x and y increase right and up.
我在一些文本输出中添加了显示度数和图像片段的显示.
I added in some text output that shows the degrees and image segment being shown.
jQuery很好地处理了x和y位置.请注意,您的CSS设置是跨浏览器.
jQuery handles normalizing the x and y position nicely. Just take care that your CSS setup is cross browser.
这是我们的形象:
这是我们的HTML:
<div id="main"><div id="img"></div></div>
<div id="info">
<span></span><br/>
<span></span>
</div>
CSS:
div#main {
width:500px;
height:500px;
border:2px #000 solid; }
div#img {
width:94px;
height:119px;
overflow:hidden;
top:50%;
left:50%;
margin-left:-45px;
margin-top:-60px;
position:relative;
background-image:url('http://imgur.com/3UPki.png');
background-position:0;}
div#info {
position: absolute;
bottom:0;
left:0; }
JavaScript/jQuery:
$(function() {
var position = $("div#img").position(),
mouseX, mouseY, imgX, imgY, degree;
imgX = position.left;
imgY = position.top;
$("#main").mousemove(function(e) {
// degree is arctan y over x (soh,cah,toa)
degree = Math.atan2((e.pageY - imgY),(e.pageX - imgX))*(180 / Math.PI);
degree = (degree - 90) % 360;
// jQuery normalizes pageX and pageY
// transfrom from -180 to 180 ==> 0 to 360
if (degree < 0) degree = 180 + (180 - (Math.abs(degree)));
rotate(degree);
$("span:first").html("Segment: " + (9 - Math.floor(degree / 36)));
$("span:last").html("Degree: " + Math.floor(degree));
});
function rotate(degree) {
var off = 9 - Math.floor(degree / 36);
$("div#img").css("background-position",-off*94);
}
});
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