这篇文章将为大家详细讲解有关HTML5中怎么通过绘制点线面组成一个3D图形,文章内容质量较高,因此小编分享给大家做个参考,希望大家阅读完这篇文章后对相关知识有一定的了解。
3D立方体
做一个立方体,我用了三个对象:点对象,面对象,以及立方体本身一个对象:
下面这个是点对象,x,y,z是点的三维坐标,_get2d方法是把三维坐标转换到二维层面来。fallLength是焦距。
XML/HTML Code复制内容到剪贴板
var Vector = function(x,y,z){
this.x = x;
this.y = y;
this.z = z;
this._get2d = function(){
var scale = fallLength/(fallLength+this.z);
var x = centerX + this.x*scale;
var y = centerY + this.y*scale;
return {x:x , y:y};
}
}
然后是面对象:
面对象的属性页很容易理解,一个面就是一个正方形 , v1v2v3v4是面的四个顶点,zIndex这个属性很重要,是代表这个面的层级,是在最外面还是在里面,这个必须要有,这样当用canvas画的时候才能让这个面画在最前面,才不会被其他的面遮盖。zIndex的值也很容易理解,就是顶点z轴坐标的平均值,其实也就是中心点的z轴坐标。颜色就是这个面的颜色啦。
XML/HTML Code复制内容到剪贴板
var Face = function(vector1,vector2,vector3,vector4,color){
this.v1 = vector1;
this.v2 = vector2;
this.v3 = vector3;
this.v4 = vector4;
this.color = color;
this.zIndex = (this.v1.z + this.v2.z + this.v3.z + this.v4.z)/4;
this.draw = function(){
ctx.save();
ctx.beginPath();
ctx.moveTo(this.v1._get2d().x , this.v1._get2d().y);
ctx.lineTo(this.v2._get2d().x , this.v2._get2d().y);
ctx.lineTo(this.v3._get2d().x , this.v3._get2d().y);
ctx.lineTo(this.v4._get2d().x , this.v4._get2d().y);
ctx.closePath();
// ctx.fillStyle = "rgba("+parseInt(Math.random()*255)+","+parseInt(Math.random()*255)+","+parseInt(Math.random()*255)+",0.2)";
ctx.fillStyle = this.color;
ctx.fill();
}
}
最后是立方体本身对象:
因为立方体最后要旋转,所以,立方体对象里面不仅有面对象,还要有点对象,点旋转后才会引起面的旋转。length是立方体的边长,_initVector是初始化立方体的各个顶点,_draw方法就是把所有点形成面,将面放入数组,然后对面进行排序(就是根据面里的zIndex排序),排序好后,调用每个面里的draw方法。立方体就出来了。
XML/HTML Code复制内容到剪贴板
var Cube = function(length){
this.length = length;
this.faces = [];
this.vectors = [];
}
Cube.prototype = {
_initVector:function(){
this.vectors[0] = new Vector(-this.length/2 , -this.length/2 , this.length/2);
this.vectors[1] = new Vector(-this.length/2 , this.length/2 , this.length/2);
this.vectors[2] = new Vector(this.length/2 , -this.length/2 , this.length/2);
this.vectors[3] = new Vector(this.length/2 , this.length/2 , this.length/2);
this.vectors[4] = new Vector(this.length/2 , -this.length/2 , -this.length/2);
this.vectors[5] = new Vector(this.length/2 , this.length/2 , -this.length/2);
this.vectors[6] = new Vector(-this.length/2 , -this.length/2 , -this.length/2);
this.vectors[7] = new Vector(-this.length/2 , this.length/2 , -this.length/2);
},
_draw:function(){
this.faces[0] = new Face(this.vectors[0] , this.vectors[1] , this.vectors[3] , this.vectors[2] , "#6c6");
this.faces[1] = new Face(this.vectors[2] , this.vectors[3] , this.vectors[5] , this.vectors[4] , "#6cc");
this.faces[2] = new Face(this.vectors[4] , this.vectors[5] , this.vectors[7] , this.vectors[6] , "#cc6");
this.faces[3] = new Face(this.vectors[6] , this.vectors[7] , this.vectors[1] , this.vectors[0] , "#c6c");
this.faces[4] = new Face(this.vectors[1] , this.vectors[3] , this.vectors[5] , this.vectors[7] , "#666");
this.faces[5] = new Face(this.vectors[0] , this.vectors[2] , this.vectors[4] , this.vectors[6] , "#ccc");
this.faces.sort(function(a , b){
return b.zIndex - a.zIndex;
});
this.faces.foreach(function(){
this.draw();
})
}
}
立方体做好了,接下来就可以让它动起来了。根据鼠标位置改变立方体转动的角度。rotateX和rotateY方法就是让所有点绕X轴旋转以及绕Y轴旋转。这个的原理我在之前那个博文上好像有说过。。。。如果想了解更多,可以自己去百度一下计算机图形学3D变换。绕X轴和绕Y轴是最简单的旋转矩阵了。当然,如果有兴趣的还可以去搜一下绕任意轴旋转矩阵。。。这个有点复杂,我本来想用它来做个魔方,不过遇到一些问题,暂时还没解决。好吧,扯远了。通过rotateX和rotateY两个方法可以让每个点获得下一帧的位置,在动画循环中重绘。这样,转动的立方体就做出来了。
XML/HTML Code复制内容到剪贴板
if("addEventListener" in window){
window.addEventListener("mousemove" , function(event){
var x = event.clientX - canvas.offsetLeft - centerX;
var y = event.clientY - canvas.offsetTop - centerY;
angleY = x*0.0001;
angleX = y*0.0001;
});
}
else {
window.attachEvent("onmousemove" , function(event){
var x = event.clientX - canvas.offsetLeft - centerX;
var y = event.clientY - canvas.offsetTop - centerY;
angleY = x*0.0001;
angleX = y*0.0001;
});
}
function rotateX(vectors){
var cos = Math.cos(angleX);
var sin = Math.sin(angleX);
vectors.foreach(function(){
var y1 = this.y * cos - this.z * sin;
var z1 = this.z * cos + this.y * sin;
this.y = y1;
this.z = z1;
});
}
function rotateY(vectors){
var cos = Math.cos(angleY);
var sin = Math.sin(angleY);
vectors.foreach(function(){
var x1 = this.x * cos - this.z * sin;
var z1 = this.z * cos + this.x * sin;
this.x = x1;
this.z = z1;
})
}
cube = new Cube(80);
cube._initVector();
function initAnimate(){
cube._draw();
animate();
}
function animate(){
ctx.clearRect(0,0,canvas.width,canvas.height)
rotateY(cube.vectors);
rotateX(cube.vectors);
cube._draw();
if("requestAnimationFrame" in window){
requestAnimationFrame(animate);
}
else if("webkitRequestAnimationFrame" in window){
webkitRequestAnimationFrame(animate);
}
else if("msRequestAnimationFrame" in window){
msRequestAnimationFrame(animate);
}
else if("mozRequestAnimationFrame" in window){
mozRequestAnimationFrame(animate);
}
else {
setTimeout(animate , 16);
}
}
关于HTML5中怎么通过绘制点线面组成一个3D图形就分享到这里了,希望以上内容可以对大家有一定的帮助,可以学到更多知识。如果觉得文章不错,可以把它分享出去让更多的人看到。