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canvas-3d-cube.html
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canvas-3d-cube.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>3D cube HTML5 canvas realization</title>
<script type="text/javascript">
function color(r, g, b, a)
{
this.r = r;
this.g = g;
this.b = b;
this.a = a;
}
function point2D(x, y)
{
this.x = x;
this.y = y;
}
point2D.prototype.move = function(p2D)
{
this.x += p2D.x;
this.y += p2D.y;
}
function point3D(x, y, z)
{
this.x = x;
this.y = y;
this.z = z;
}
point3D.prototype.move = function(p3D)
{
this.x += p3D.x;
this.y += p3D.y;
this.z += p3D.z;
}
point3D.prototype.swap = function(p3D)
{
this.x = p3D.x;
this.y = p3D.y;
this.z = p3D.z;
}
point3D.prototype.rotate = function(axis, angleGr)
{
angleRad = angleGr * Math.PI / 180;
switch (axis)
{
case "x":
{
var tempPoint = new point3D(
this.x,
this.y * Math.cos(angleRad) - this.z * Math.sin(angleRad),
this.y * Math.sin(angleRad) + this.z * Math.cos(angleRad)
);
this.swap(tempPoint);
break;
}
case "y":
{
var tempPoint = new point3D(
this.x * Math.cos(angleRad) + this.z * Math.sin(angleRad),
this.y,
-this.x * Math.sin(angleRad) + this.z * Math.cos(angleRad)
);
this.swap(tempPoint);
break;
}
case "z":
{
var tempPoint = new point3D(
this.x * Math.cos(angleRad) - this.y * Math.sin(angleRad),
this.x * Math.sin(angleRad) + this.y * Math.cos(angleRad),
this.z
);
this.swap(tempPoint);
break;
}
}
}
function normal3D(p3D, length)
{
this.point = p3D;
this.length = length;
}
function poly()
{
var points = [];
for(var i = 0; i < arguments.length; i++)
points.push(arguments[i]);
this.points = points;
// Calculating normal
var v1 = new point3D(points[2].x - points[1].x, points[2].y - points[1].y, points[2].z - points[1].z);
var v2 = new point3D(points[0].x - points[1].x, points[0].y - points[1].y, points[0].z - points[1].z);
var normalP3D = new point3D(v1.y*v2.z-v2.y*v1.z, v1.z*v2.x-v2.z*v1.x, v1.x*v2.y-v2.x*v1.y);
var normalLen = Math.sqrt(normalP3D.x*normalP3D.x + normalP3D.y*normalP3D.y + normalP3D.z*normalP3D.z);
this.normal = new normal3D(normalP3D, normalLen);
}
poly.prototype.move = function(p3D)
{
for(var i = 0; i < this.points.length; i++)
{
var point = this.points[i];
point.move(p3D);
}
}
poly.prototype.rotate = function(axis, angle)
{
for(var i = 0; i < this.points.length; i++)
{
var point = this.points[i];
point.rotate(axis, angle);
}
this.normal.point.rotate(axis, angle);
}
poly.prototype.put = function(center, fillColor, edgeColor)
{
// Calulate visibility
var normalAngleRad = Math.acos(this.normal.point.z/this.normal.length);
if(normalAngleRad / Math.PI * 180 >= 90)
return;
var lightIntensity = 1 - 2 * (normalAngleRad / Math.PI);
ctx.fillStyle = 'rgba('+fillColor.r+','+fillColor.g+','+fillColor.b+','+(fillColor.a*lightIntensity)+')';
ctx.beginPath();
for(var i = 0; i < this.points.length; i++)
{
var point = this.points[i];
if(i)
ctx.lineTo(center.x + parseInt(point.x), center.y - parseInt(point.y));
else
ctx.moveTo(center.x + parseInt(point.x), center.y - parseInt(point.y));
}
ctx.fill();
ctx.lineWidth = 1;
ctx.strokeStyle = 'rgba('+edgeColor.r+','+edgeColor.g+','+edgeColor.b+','+(edgeColor.a*lightIntensity)+')';
ctx.beginPath();
var point = this.points[this.points.length-1];
ctx.moveTo(center.x + parseInt(point.x), center.y - parseInt(point.y));
for(var i = 0; i < this.points.length; i++)
{
var point = this.points[i];
ctx.lineTo(center.x + parseInt(point.x), center.y - parseInt(point.y));
}
ctx.stroke();
}
function Cube(size, fillColor, edgeColor)
{
var p000 = new point3D(0,0,0);
var p0S0 = new point3D(0,size,0);
var pSS0 = new point3D(size,size,0);
var pS00 = new point3D(size,0,0);
var p00S = new point3D(0,0,size);
var p0SS = new point3D(0,size,size);
var pSSS = new point3D(size,size,size);
var pS0S = new point3D(size,0,size);
var polys = [];
polys.push(new poly(p000,p0S0,pSS0,pS00));
polys.push(new poly(pS00,pSS0,pSSS,pS0S));
polys.push(new poly(pS0S,pSSS,p0SS,p00S));
polys.push(new poly(p00S,p0SS,p0S0,p000));
polys.push(new poly(p0S0,p0SS,pSSS,pSS0));
polys.push(new poly(p00S,p000,pS00,pS0S));
this.polys = polys;
var points = [];
points.push(p000);
points.push(p0S0);
points.push(pSS0);
points.push(pS00);
points.push(p00S);
points.push(p0SS);
points.push(pSSS);
points.push(pS0S);
for(var i = 0; i < polys.length; i++)
{
points.push(polys[i].normal.point);
}
this.points = points;
this.fillColor = fillColor;
this.edgeColor = edgeColor;
}
function move(o3D, p3D)
{
for(var i = 0; i < o3D.points.length - o3D.polys.length; i++)
{
var point = o3D.points[i];
point.move(p3D);
}
}
function put(o3D, center)
{
for(var i = 0; i < o3D.polys.length; i++)
{
var poly = o3D.polys[i];
poly.put(center, o3D.fillColor, o3D.edgeColor);
}
}
function rotate(o3D, axis, angle)
{
for(var i = 0; i < o3D.points.length; i++)
{
var point = o3D.points[i];
point.rotate(axis, angle);
}
}
function init(){
canvas = document.getElementById('3Dcube');
if (canvas.getContext){
ctx = canvas.getContext('2d');
ctx.fillStyle = 'rgba(0, 0, 0, 1)';
ctx.fillRect(0, 0, canvas.width, canvas.height); // clear canvas
cube = new Cube(100, new color(50,50,200,1), new color(60,60,210,1));
move(cube, new point3D(-50,-50,-50));
rotate(cube, 'x', 45);
rotate(cube, 'y', 45);
rotate(cube, 'z', 45);
centerScreen = new point2D(canvas.width / 2, canvas.height / 2);
put(cube, centerScreen);
timer = setInterval(nextFrame, 1000 / 60);
}
}
function nextFrame()
{
ctx.fillStyle = 'rgba(0, 0, 0, 1)';
ctx.fillRect(0, 0, canvas.width, canvas.height); // clear canvas
rotate(cube, 'x', 0.4);
rotate(cube, 'y', 0.6);
rotate(cube, 'z', 0.3);
ctx.fillStyle = 'rgba(50, 50, 200, 1)';
ctx.strokeStyle = 'rgba(60, 60, 210, 1)';
put(cube, centerScreen);
}
</script>
<style type="text/css">
canvas { border: 0px solid black; }
</style>
</head>
<body onload="init();">
<h1>3D cube HTML5 canvas realization on 2D contex</h1>
<p>Features:
<ul>
<li>3D operations: rotating, moving object center</li>
<li>Direct illumination</li>
<li>Highlighting edges</li>
<li>Optimizations:
<ul>
<li>Skip outputting of invisible polygons</li>
<li>Skip processing of duplicated points</li>
</ul>
</li>
</ul>
</p>
<canvas id="3Dcube" width="400" height="225"></canvas>
</body>
</html>