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分享为什么在ios上canvas动画很卡，是写法问题吗？
这是js里面的代码，大家帮忙看看，html代码为<canvas id="canv"></canvas>，安卓上很流畅，背景是可以通过手势旋转的星河图
var num = 200;
var w = window.innerWidth;
var h = window.innerHeight;
var max = 100;
var _x = 0;
var _y = 0;
var _z = 150;
var dtr = function(d) {
return d * Math.PI / 180;
};
var rnd = function() {
return Math.sin(Math.floor(Math.random() * 360) * Math.PI / 180);
};
var dist = function(p1, p2, p3) {
return Math.sqrt(Math.pow(p2.x - p1.x, 2) + Math.pow(p2.y - p1.y, 2) + Math.pow(p2.z - p1.z, 2));
};
var cam = {
obj: {
x: _x,
y: _y,
z: _z
},
dest: {
x: 0,
y: 0,
z: 1
},
dist: {
x: 0,
y: 0,
z: 200
},
ang: {
cplane: 0,
splane: 0,
ctheta: 0,
stheta: 0
},
zoom: 1,
disp: {
x: w / 2,
y: h / 2,
z: 0
},
upd: function() {
cam.dist.x = cam.dest.x - cam.obj.x;
cam.dist.y = cam.dest.y - cam.obj.y;
cam.dist.z = cam.dest.z - cam.obj.z;
cam.ang.cplane = -cam.dist.z / Math.sqrt(cam.dist.x * cam.dist.x + cam.dist.z * cam.dist.z);
cam.ang.splane = cam.dist.x / Math.sqrt(cam.dist.x * cam.dist.x + cam.dist.z * cam.dist.z);
cam.ang.ctheta = Math.sqrt(cam.dist.x * cam.dist.x + cam.dist.z * cam.dist.z) / Math.sqrt(cam.dist.x * cam.dist.x + cam.dist.y * cam.dist.y + cam.dist.z * cam.dist.z);
cam.ang.stheta = -cam.dist.y / Math.sqrt(cam.dist.x * cam.dist.x + cam.dist.y * cam.dist.y + cam.dist.z * cam.dist.z);
}
};
var trans = {
parts: {
sz: function(p, sz) {
return {
x: p.x * sz.x,
y: p.y * sz.y,
z: p.z * sz.z
};
},
rot: {
x: function(p, rot) {
return {
x: p.x,
y: p.y * Math.cos(dtr(rot.x)) - p.z * Math.sin(dtr(rot.x)),
z: p.y * Math.sin(dtr(rot.x)) + p.z * Math.cos(dtr(rot.x))
};
},
y: function(p, rot) {
return {
x: p.x * Math.cos(dtr(rot.y)) + p.z * Math.sin(dtr(rot.y)),
y: p.y,
z: -p.x * Math.sin(dtr(rot.y)) + p.z * Math.cos(dtr(rot.y))
};
},
z: function(p, rot) {
return {
x: p.x * Math.cos(dtr(rot.z)) - p.y * Math.sin(dtr(rot.z)),
y: p.x * Math.sin(dtr(rot.z)) + p.y * Math.cos(dtr(rot.z)),
z: p.z
};
}
},
pos: function(p, pos) {
return {
x: p.x + pos.x,
y: p.y + pos.y,
z: p.z + pos.z
};
}
},
pov: {
plane: function(p) {
return {
x: p.x * cam.ang.cplane + p.z * cam.ang.splane,
y: p.y,
z: p.x * -cam.ang.splane + p.z * cam.ang.cplane
};
},
theta: function(p) {
return {
x: p.x,
y: p.y * cam.ang.ctheta - p.z * cam.ang.stheta,
z: p.y * cam.ang.stheta + p.z * cam.ang.ctheta
};
},
set: function(p) {
return {
x: p.x - cam.obj.x,
y: p.y - cam.obj.y,
z: p.z - cam.obj.z
};
}
},
persp: function(p) {
return {
x: p.x * cam.dist.z / p.z * cam.zoom,
y: p.y * cam.dist.z / p.z * cam.zoom,
z: p.z * cam.zoom,
p: cam.dist.z / p.z
};
},
disp: function(p, disp) {
return {
x: p.x + disp.x,
y: -p.y + disp.y,
z: p.z + disp.z,
p: p.p
};
},
steps: function(_obj_, sz, rot, pos, disp) {
var _args = trans.parts.sz(_obj_, sz);
_args = trans.parts.rot.x(_args, rot);
_args = trans.parts.rot.y(_args, rot);
_args = trans.parts.rot.z(_args, rot);
_args = trans.parts.pos(_args, pos);
_args = trans.pov.plane(_args);
_args = trans.pov.theta(_args);
_args = trans.pov.set(_args);
_args = trans.persp(_args);
_args = trans.disp(_args, disp);
return _args;
}
};
(function() {
"use strict";
var threeD = function(param) {
this.transIn = {};
this.transOut = {};
this.transIn.vtx = (param.vtx);
this.transIn.sz = (param.sz);
this.transIn.rot = (param.rot);
this.transIn.pos = (param.pos);
};
threeD.prototype.vupd = function() {
this.transOut = trans.steps(
this.transIn.vtx,
this.transIn.sz,
this.transIn.rot,
this.transIn.pos,
cam.disp
);
};
var Build = function() {
this.vel = 0.04;
this.lim = 360;
this.diff = 200;
this.initPos = 100;
this.toX = _x;
this.toY = _y;
this.go();
};
Build.prototype.go = function() {
this.canvas = document.getElementById("canv");
this.canvas.width = window.innerWidth;
this.canvas.height = window.innerHeight;
this.$ = canv.getContext("2d");
this.$.globalCompositeOperation = 'source-over';
this.varr = [];
this.dist = [];
this.calc = [];
for (var i = 0, len = num; i < len; i++) {
this.add();
}
this.rotObj = {
x: 0,
y: 0,
z: 0
};
this.objSz = {
x: w / 5,
y: h / 5,
z: w / 5
};
};
Build.prototype.add = function() {
this.varr.push(new threeD({
vtx: {
x: rnd(),
y: rnd(),
z: rnd()
},
sz: {
x: 0,
y: 0,
z: 0
},
rot: {
x: 20,
y: -20,
z: 0
},
pos: {
x: this.diff * Math.sin(360 * Math.random() * Math.PI / 180),
y: this.diff * Math.sin(360 * Math.random() * Math.PI / 180),
z: this.diff * Math.sin(360 * Math.random() * Math.PI / 180)
}
}));
this.calc.push({
x: 360 * Math.random(),
y: 360 * Math.random(),
z: 360 * Math.random()
});
};
Build.prototype.upd = function() {
cam.obj.x += (this.toX - cam.obj.x) * 0.05;
cam.obj.y += (this.toY - cam.obj.y) * 0.05;
};
Build.prototype.draw = function() {
this.$.clearRect(0, 0, this.canvas.width, this.canvas.height);
cam.upd();
this.rotObj.x += 0.1;
this.rotObj.y += 0.1;
this.rotObj.z += 0.1;
for (var i = 0; i < this.varr.length; i++) {
for (var val in this.calc[i]) {
if (this.calc[i].hasOwnProperty(val)) {
this.calc[i][val] += this.vel;
if (this.calc[i][val] > this.lim) this.calc[i][val] = 0;
}
}
this.varr[i].transIn.pos = {
x: this.diff * Math.cos(this.calc[i].x * Math.PI / 180),
y: this.diff * Math.sin(this.calc[i].y * Math.PI / 180),
z: this.diff * Math.sin(this.calc[i].z * Math.PI / 180)
};
this.varr[i].transIn.rot = this.rotObj;
this.varr[i].transIn.sz = this.objSz;
this.varr[i].vupd();
if (this.varr[i].transOut.p < 0) continue;
var g = this.$.createRadialGradient(this.varr[i].transOut.x, this.varr[i].transOut.y, this.varr[i].transOut.p, this.varr[i].transOut.x, this.varr[i].transOut.y, this.varr[i].transOut.p * 2);
this.$.globalCompositeOperation = 'lighter';
g.addColorStop(0, 'hsla(255, 255%, 255%, 1)');
g.addColorStop(.5, 'hsla(' + (i + 2) + ',85%, 40%,1)');
g.addColorStop(1, 'hsla(' + (i) + ',85%, 40%,.5)');
this.$.fillStyle = g;
this.$.beginPath();
this.$.arc(this.varr[i].transOut.x, this.varr[i].transOut.y, this.varr[i].transOut.p * 2, 0, Math.PI * 2, false);
this.$.fill();
this.$.closePath();
}
};
Build.prototype.anim = function() {
window.requestAnimationFrame = (function() {
return window.requestAnimationFrame ||
function(callback, element) {
window.setTimeout(callback, 1000 / 60);
};
})();
var anim = function() {
this.upd();
this.draw();
window.requestAnimationFrame(anim);
}.bind(this);
window.requestAnimationFrame(anim);
};
Build.prototype.run = function() {
this.anim();
window.addEventListener('mousemove', function(e) {
this.toX = (e.clientX - this.canvas.width / 2) * -0.8;
this.toY = (e.clientY - this.canvas.height / 2) * 0.8;
}.bind(this));
window.addEventListener('touchmove', function(e) {
if (event.cancelable) {
if (!event.defaultPrevented) {
event.preventDefault();
}
}
this.toX = (e.touches[0].clientX - this.canvas.width / 2) * -0.8;
this.toY = (e.touches[0].clientY - this.canvas.height / 2) * 0.8;
}.bind(this));
window.addEventListener('mousedown', function(e) {
for (var i = 0; i < 100; i++) {
this.add();
}
}.bind(this));
window.addEventListener('touchstart', function(e) {
if (event.cancelable) {
if (!event.defaultPrevented) {
event.preventDefault();
}
}
for (var i = 0; i < 100; i++) {
this.add();
}
}.bind(this));
};
var app = new Build();
app.run();
})();
window.addEventListener('resize', function() {
canvas.width = w = window.innerWidth;
canvas.height = h = window.innerHeight;
}, false);
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