本教程的主题是利用HTML5技术在2D和3D图形之间搭一座互通的桥梁(通过WebGL方式)。今天我将展示如何使用一个多边形网格绘制一个三维对象。
一个多边形网格或非结构化网格是一个集合的顶点,边缘和面孔,在3
d电脑图像和实体建模定义了一个多面体的对象的形状。通常由三角形的面孔,四边形或其他简单凸多边形,因为这样可以简化渲染,但也可能是由更一般的凹多边
形,或多边形的洞。
为了演示,我们准备了简单的三维物体——一个多维数据集和多维领域
HTML CODE
通常我们会在canvas里做一个简单的标记
Triangle mesh for 3D objects in HTML5 | Script Tutorials
<script><br> //var obj = new cube();<br> //var obj = new sphere(6);<br> var obj = new sphere(16);<br> </script>
Please use Up / Down keys to change opacity
我提取一个生成的对象初始化来:
<script><br> //var obj = new cube();<br> //var obj = new sphere(6);<br> var obj = new sphere(16);<br></script>
这意味着如果我们需要显示一个多维数据集——你必须取消第一个一行,如果你想显示一个球体与6张面孔——选择第二个变体。
JS CODE
JS的代码分为三部分:主体的代码,网格代码和转换代码
meshes.js
// get random color
function getRandomColor() {
var letters = '0123456789ABCDEF'.split('');
var color = '#';
for (var i = 0; i color += letters[Math.round(Math.random() * 15)];
}
return color;
}
// prepare object
function prepareObject(o) {
o.colors = new Array();
// prepare normals
o.normals = new Array();
for (var i = 0; i o.normals[i] = [0, 0, 0];
o.colors[i] = getRandomColor();
}
// prepare centers: calculate max positions
o.center = [0, 0, 0];
for (var i = 0; i o.center[0] += o.points[i][0];
o.center[1] += o.points[i][1];
o.center[2] += o.points[i][2];
}
// prepare distances
o.distances = new Array();
for (var i = 1; i o.distances[i] = 0;
}
// calculate average center positions
o.points_number = o.points.length;
o.center[0] = o.center[0] / (o.points_number - 1);
o.center[1] = o.center[1] / (o.points_number - 1);
o.center[2] = o.center[2] / (o.points_number - 1);
o.faces_number = o.faces.length;
o.axis_x = [1, 0, 0];
o.axis_y = [0, 1, 0];
o.axis_z = [0, 0, 1];
}
// Cube object
function cube() {
// prepare points and faces for cube
this.points=[
[0,0,0],
[100,0,0],
[100,100,0],
[0,100,0],
[0,0,100],
[100,0,100],
[100,100,100],
[0,100,100],
[50,50,100],
[50,50,0],
];
this.faces=[
[0,4,5],
[0,5,1],
[1,5,6],
[1,6,2],
[2,6,7],
[2,7,3],
[3,7,4],
[3,4,0],
[8,5,4],
[8,6,5],
[8,7,6],
[8,4,7],
[9,5,4],
[9,6,5],
[9,7,6],
[9,4,7],
];
prepareObject(this);
}
// Sphere object
function sphere(n) {
var delta_angle = 2 * Math.PI / n;
// prepare vertices (points) of sphere
var vertices = [];
for (var j = 0; j for (var i = 0; i vertices[j * n + i] = [];
vertices[j * n + i][0] = 100 * Math.sin((j + 1) * delta_angle) * Math.cos(i * delta_angle);
vertices[j * n + i][1] = 100 * Math.cos((j + 1) * delta_angle);
vertices[j * n + i][2] = 100 * Math.sin((j + 1) * delta_angle) * Math.sin(i * delta_angle);
}
}
vertices[(n / 2 - 1) * n] = [];
vertices[(n / 2 - 1) * n + 1] = [];
vertices[(n / 2 - 1) * n][0] = 0;
vertices[(n / 2 - 1) * n][1] = 100;
vertices[(n / 2 - 1) * n][2] = 0;
vertices[(n / 2 - 1) * n + 1][0] = 0;
vertices[(n / 2 - 1) * n + 1][1] = -100;
vertices[(n / 2 - 1) * n + 1][2] = 0;
this.points = vertices;
// prepare faces
var faces = [];
for (var j = 0; j for (var i = 0; i faces[j * 2 * n + i] = [];
faces[j * 2 * n + i + n] = [];
faces[j * 2 * n + i][0] = j * n + i;
faces[j * 2 * n + i][1] = j * n + i + 1;
faces[j * 2 * n + i][2] = (j + 1) * n + i + 1;
faces[j * 2 * n + i + n][0] = j * n + i;
faces[j * 2 * n + i + n][1] = (j + 1) * n + i + 1;
faces[j * 2 * n + i + n][2] = (j + 1) * n + i;
}
faces[j * 2 * n + n - 1] = [];
faces[2 * n * (j + 1) - 1] = [];
faces[j * 2 * n + n - 1 ][0] = (j + 1) * n - 1;
faces[j * 2 * n + n - 1 ][1] = (j + 1) * n;
faces[j * 2 * n + n - 1 ][2] = j * n;
faces[2 * n * (j + 1) - 1][0] = (j + 1) * n - 1;
faces[2 * n * (j + 1) - 1][1] = j * n + n;
faces[2 * n * (j + 1) - 1][2] = (j + 2) * n - 1;
}
for (var i = 0; i faces[n * (n - 4) + i] = [];
faces[n * (n - 3) + i] = [];
faces[n * (n - 4) + i][0] = (n / 2 - 1) * n;
faces[n * (n - 4) + i][1] = i;
faces[n * (n - 4) + i][2] = i + 1;
faces[n * (n - 3) + i][0] = (n / 2 - 1) * n + 1;
faces[n * (n - 3) + i][1] = (n / 2 - 2) * n + i + 1;
faces[n * (n - 3) + i][2] = (n / 2 - 2) * n + i;
}
faces[n * (n - 3) - 1] = [];
faces[n * (n - 2) - 1] = [];
faces[n * (n - 3) - 1][0] = (n / 2 - 1) * n;
faces[n * (n - 3) - 1][1] = n - 1;
faces[n * (n - 3) - 1][2] = 0;
faces[n * (n - 2) - 1][0] = (n / 2 - 1) * n + 1;
faces[n * (n - 2) - 1][1] = (n / 2 - 2) * n;
faces[n * (n - 2) - 1][2] = (n / 2 - 2) * n + n - 1;
this.faces=faces;
prepareObject(this);
}
main.js
// inner variables
var canvas, ctx;
var vAlpha = 0.5;
var vShiftX = vShiftY = 0;
var distance = -700;
var vMouseSens = 0.05;
var iHalfX, iHalfY;
// initialization
function sceneInit() {
// prepare canvas and context objects
canvas = document.getElementById('scene');
ctx = canvas.getContext('2d');
iHalfX = canvas.width / 2;
iHalfY = canvas.height / 2;
// initial scale and translate
scaleObj([3, 3, 3], obj);
translateObj([-obj.center[0], -obj.center[1], -obj.center[2]],obj);
translateObj([0, 0, -1000], obj);
// attach event handlers
document.onkeydown = handleKeydown;
canvas.onmousemove = handleMousemove;
// main scene loop
setInterval(drawScene, 25);
}
// onKeyDown event handler
function handleKeydown(e) {
kCode = ((e.which) || (e.keyCode));
switch (kCode) {
case 38: vAlpha = (vAlpha case 40: vAlpha = (vAlpha >= 0.2) ? (vAlpha - 0.1) : vAlpha; break; // Down key
}
}
// onMouseMove event handler
function handleMousemove(e) {
var x = e.pageX - canvas.offsetLeft;
var y = e.pageY - canvas.offsetTop;
if ((x > 0) && (x 0) && (y vShiftY = vMouseSens * (x - iHalfX) / iHalfX;
vShiftX = vMouseSens * (y - iHalfY) / iHalfY;
}
}
// draw main scene function
function drawScene() {
// clear canvas
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
// set fill color, stroke color, line width and global alpha
ctx.strokeStyle = 'rgb(0,0,0)';
ctx.lineWidth = 0.5;
ctx.globalAlpha= vAlpha;
// vertical and horizontal rotate
var vP1x = getRotationPar([0, 0, -1000], [1, 0, 0], vShiftX);
var vP2x = getRotationPar([0, 0, 0], [1, 0, 0], vShiftX);
var vP1y = getRotationPar([0, 0, -1000], [0, 1, 0], vShiftY);
var vP2y = getRotationPar([0, 0, 0], [0, 1, 0], vShiftY);
rotateObj(vP1x, vP2x, obj);
rotateObj(vP1y, vP2y, obj);
// recalculate distances
for (var i = 0; i obj.distances[i] = Math.pow(obj.points[i][0],2) + Math.pow(obj.points[i][1],2) + Math.pow(obj.points[i][2], 2);
}
// prepare array with face triangles (with calculation of max distance for every face)
var iCnt = 0;
var aFaceTriangles = new Array();
for (var i = 0; i var max = obj.distances[obj.faces[i][0]];
for (var f = 1; f if (obj.distances[obj.faces[i][f]] > max)
max = obj.distances[obj.faces[i][f]];
}
aFaceTriangles[iCnt++] = {faceVertex:obj.faces[i], faceColor:obj.colors[i], distance:max};
}
aFaceTriangles.sort(sortByDistance);
// prepare array with projected points
var aPrjPoints = new Array();
for (var i = 0; i aPrjPoints[i] = project(distance, obj.points[i], iHalfX, iHalfY);
}
// draw an object (surfaces)
for (var i = 0; i
ctx.fillStyle = aFaceTriangles[i].faceColor;
// begin path
ctx.beginPath();
// face vertex index
var iFaceVertex = aFaceTriangles[i].faceVertex;
// move to initial position
ctx.moveTo(aPrjPoints[iFaceVertex[0]][0], aPrjPoints[iFaceVertex[0]][1]);
// and draw three lines (to build a triangle)
for (var z = 1; z ctx.lineTo(aPrjPoints[iFaceVertex[z]][0], aPrjPoints[iFaceVertex[z]][1]);
}
// close path, strole and fill a triangle
ctx.closePath();
ctx.stroke();
ctx.fill();
}
}
// sort function
function sortByDistance(x, y) {
return (y.distance - x.distance);
}
// initialization
if (window.attachEvent) {
window.attachEvent('onload', sceneInit);
} else {
if (window.onload) {
var curronload = window.onload;
var newonload = function() {
curronload();
sceneInit();
};
window.onload = newonload;
} else {
window.onload = sceneInit;
}
}
查看演示:http://www.script-tutorials.com/demos/319/index.html

H5 improves web user experience with multimedia support, offline storage and performance optimization. 1) Multimedia support: H5 and elements simplify development and improve user experience. 2) Offline storage: WebStorage and IndexedDB allow offline use to improve the experience. 3) Performance optimization: WebWorkers and elements optimize performance to reduce bandwidth consumption.

HTML5 code consists of tags, elements and attributes: 1. The tag defines the content type and is surrounded by angle brackets, such as. 2. Elements are composed of start tags, contents and end tags, such as contents. 3. Attributes define key-value pairs in the start tag, enhance functions, such as. These are the basic units for building web structure.

HTML5 is a key technology for building modern web pages, providing many new elements and features. 1. HTML5 introduces semantic elements such as, , etc., which enhances web page structure and SEO. 2. Support multimedia elements and embed media without plug-ins. 3. Forms enhance new input types and verification properties, simplifying the verification process. 4. Offer offline and local storage functions to improve web page performance and user experience.

Best practices for H5 code include: 1. Use correct DOCTYPE declarations and character encoding; 2. Use semantic tags; 3. Reduce HTTP requests; 4. Use asynchronous loading; 5. Optimize images. These practices can improve the efficiency, maintainability and user experience of web pages.

Web standards and technologies have evolved from HTML4, CSS2 and simple JavaScript to date and have undergone significant developments. 1) HTML5 introduces APIs such as Canvas and WebStorage, which enhances the complexity and interactivity of web applications. 2) CSS3 adds animation and transition functions to make the page more effective. 3) JavaScript improves development efficiency and code readability through modern syntax of Node.js and ES6, such as arrow functions and classes. These changes have promoted the development of performance optimization and best practices of web applications.

H5 is not just the abbreviation of HTML5, it represents a wider modern web development technology ecosystem: 1. H5 includes HTML5, CSS3, JavaScript and related APIs and technologies; 2. It provides a richer, interactive and smooth user experience, and can run seamlessly on multiple devices; 3. Using the H5 technology stack, you can create responsive web pages and complex interactive functions.

H5 and HTML5 refer to the same thing, namely HTML5. HTML5 is the fifth version of HTML, bringing new features such as semantic tags, multimedia support, canvas and graphics, offline storage and local storage, improving the expressiveness and interactivity of web pages.

H5referstoHTML5,apivotaltechnologyinwebdevelopment.1)HTML5introducesnewelementsandAPIsforrich,dynamicwebapplications.2)Itsupportsmultimediawithoutplugins,enhancinguserexperienceacrossdevices.3)SemanticelementsimprovecontentstructureandSEO.4)H5'srespo


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