实例介绍
【实例简介】
【实例截图】
【核心代码】
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<html>
<head>
<title>ExplorerCanvas Example 1</title>
<!--[if IE]><script type="text/javascript" src="../excanvas.js"></script><![endif]-->
<script type="text/javascript">
/* -------------------------------------------------------------------- */
var canvas, ctx;
var canvasWidth, halfCanvasWidth;
var canvasHeight, halfCanvasHeight;
var space; // 3D Engine
var scene; // 3D Scene
/* -------------------------------------------------------------------- */
/**
* Space is a simple 3D system.
*
* Y = up
* Z = into screen
* X = right
*/
function Space() {
this.m = this.createMatrixIdentity();
this.mStack = [];
}
Space.prototype.createMatrixIdentity = function() {
return [
[1, 0, 0, 0],
[0, 1, 0, 0],
[0, 0, 1, 0],
[0, 0, 0, 1]
];
}
/**
* Multiplies two 4x4 matricies together.
*/
Space.prototype.matrixMultiply = function(m1, m2) {
var result = this.createMatrixIdentity();
var width = m1[0].length;
var height = m1.length;
if (width != m2.length) {
// error
}
for (var x = 0; x < width; x ) {
for (var y = 0; y < height; y ) {
var sum = 0;
for (var z = 0; z < width; z ) {
sum = m1[y][z] * m2[z][x];
}
result[y][x] = sum;
}
}
return result;
}
/**
* Transforms a coordinate using the current transformation
* matrix, then flattens it using the projection matrix.
*/
Space.prototype.flatten = function(point) {
var p = [[point.x, point.y, point.z, 1]];
var pm = this.matrixMultiply(p, this.m);
point.tx = pm[0][0];
point.ty = pm[0][1];
point.tz = pm[0][2];
// lazy projection
point.fx = halfCanvasWidth (canvasWidth * point.tx / point.tz);
point.fy = halfCanvasHeight -(canvasWidth * point.ty / point.tz);
}
/**
* Translate (move) the current transformation matrix
*/
Space.prototype.translate = function(x, y, z) {
var m = [
[1, 0, 0, 0],
[0, 1, 0, 0],
[0, 0, 1, 0],
[x, y, z, 1]
];
this.m = this.matrixMultiply(m, this.m);
}
/**
* Rotate the current transformation matrix. Rotations are
* world-oriented, and occur in y,x,z order.
*/
Space.prototype.rotate = function(x, y, z) {
if (y) {
var cosY = Math.cos(y);
var sinY = Math.sin(y);
var rotY = [
[cosY, 0, sinY, 0],
[0, 1, 0, 0],
[-sinY, 0, cosY, 0],
[0, 0, 0, 1]
];
this.m = this.matrixMultiply(this.m, rotY);
}
if (x) {
var cosX = Math.cos(x);
var sinX = Math.sin(x);
var rotX = [
[1, 0, 0, 0],
[0, cosX, -sinX, 0],
[0, sinX, cosX,0],
[0, 0, 0, 1]
];
this.m = this.matrixMultiply(this.m, rotX);
}
if (z) {
var cosZ = Math.cos(z);
var sinZ = Math.sin(z);
var rotZ = [
[cosZ, -sinZ, 0, 0],
[sinZ, cosZ, 0, 0],
[0, 0, 1, 0],
[0, 0, 0, 1]
];
this.m = this.matrixMultiply(this.m, rotZ);
}
}
/**
* Pushes the current transformation onto the stack
*/
Space.prototype.push = function() {
this.mStack.push(this.m);
this.m = [
[this.m[0][0], this.m[0][1], this.m[0][2], this.m[0][3]],
[this.m[1][0], this.m[1][1], this.m[1][2], this.m[1][3]],
[this.m[2][0], this.m[2][1], this.m[2][2], this.m[2][3]],
[this.m[3][0], this.m[3][1], this.m[3][2], this.m[3][3]]
];
}
/**
* Pops the end off the transformation stack
*/
Space.prototype.pop = function() {
this.m = this.mStack.pop();
}
/* -------------------------------------------------------------------- */
/**
* A 3d coordinate
*/
function Point(x, y, z) {
this.x = x;
this.y = y;
this.z = z;
// Relative to camera coordinates
this.tx;
this.ty;
this.tz;
// Flattened coordinates
this.fx;
this.fy;
}
/**
* A Shape is made up of polygons
*/
function Shape() {
this.points = [];
this.polygons = [];
}
/**
* Draws the shape
*/
Shape.prototype.draw = function(drawlist) {
for (var i = 0; i< this.points.length; i ) {
space.flatten(this.points[i]);
}
for (var i = 0; i< this.polygons.length; i ) {
var poly = this.polygons[i]; // convenience
space.flatten(poly.origin);
// lazy backface culling
if (poly.normal && this.backface) {
space.flatten(poly.normal);
var originDist = Math.pow(poly.origin.tx, 2)
Math.pow(poly.origin.ty, 2)
Math.pow(poly.origin.tz, 2);
var normalDist = Math.pow(poly.normal.tx, 2)
Math.pow(poly.normal.ty, 2)
Math.pow(poly.normal.tz, 2);
if(originDist > normalDist) {
drawlist.push(poly);
}
} else {
drawlist.push(poly);
}
}
}
/**
* A polygon is a connection of points in the shape object. You
* should probably try to make them coplanar.
*/
function Polygon(points, normal, backface, type, color) {
this.points = points;
this.origin = new Point(0, 0, 0);
for(var i = 0; i < this.points.length; i ) {
this.origin.x = this.points[i].x;
this.origin.y = this.points[i].y;
this.origin.z = this.points[i].z;
}
this.origin.x /= this.points.length;
this.origin.y /= this.points.length;
this.origin.z /= this.points.length;
if (normal) {
this.normal = new Point(this.origin.x normal.x,
this.origin.y normal.y,
this.origin.z normal.z);
} else {
this.normal = null;
}
this.backface = backface;
this.type = type;
this.color = color;
}
Polygon.SOLID = 0;
Polygon.WIRE = 1;
/**
* Draws the polygon. Assumes that the points have already been
* flattened.
*/
Polygon.prototype.draw = function() {
ctx.beginPath();
ctx.moveTo(this.points[0].fx, this.points[0].fy);
for(var i = 0; i < this.points.length; i ) {
ctx.lineTo(this.points[i].fx, this.points[i].fy);
}
ctx.closePath();
var color = this.color;
/*
// Do lighting here
lightvector = Math.abs(this.normal.x this.normal.y);
if(lightvector > 1) {
lightvector = 1;
}
color[0] = (color[0] * lightvector).toString();
color[1] = (color[1] * lightvector).toString();
color[2] = (color[2] * lightvector).toString();
*/
if (color.length > 3) {
var style = ["rgba(",
color[0], ",",
color[1], ",",
color[2], ",",
color[3], ")"].join("");
} else {
var style = ["rgb(",
color[0], ",",
color[1], ",",
color[2], ")"].join("");
}
if (this.type == Polygon.SOLID) {
ctx.fillStyle = style;
ctx.fill();
} else if (this.type == Polygon.WIRE) {
ctx.strokeStyle = style;
ctx.stroke();
}
}
/* -------------------------------------------------------------------- */
/**
* Scene describes the 3D environment
*/
function Scene() {
this.shapes = {};
this.camera = new Point(0, 0, 0);
this.cameraTarget = new Point(0, 0, 0);
this.cameraRotation = 0;
this.drawlist = [];
}
/**
* Draw the world
*/
Scene.prototype.draw = function() {
space.push();
// Camera transformation
space.translate(
-this.camera.x,
-this.camera.y,
-this.camera.z
);
// Camera rotation
var xdiff = this.cameraTarget.x - this.camera.x;
var ydiff = this.cameraTarget.y - this.camera.y;
var zdiff = this.cameraTarget.z - this.camera.z;
var xzdist = Math.sqrt(Math.pow(xdiff, 2) Math.pow(zdiff, 2));
var xrot = -Math.atan2(ydiff, xzdist); // up/down rotation
var yrot = Math.atan2(xdiff, zdiff); // left/right rotation
space.rotate(xrot, yrot, this.cameraRotation);
// Drawing
this.drawlist = [];
for(var i in this.shapes) {
this.shapes[i].draw(this.drawlist);
}
// Depth sorting (warning: this is only enough to drive this demo - feel
// free to contribute a better system).
this.drawlist.sort(function (poly1, poly2) {
return poly2.origin.tz - poly1.origin.tz;
});
for (var i = 0; i < this.drawlist.length; i ) {
this.drawlist[i].draw();
}
space.pop();
}
/* -------------------------------------------------------------------- */
var count = 0;
function loop() {
ctx.clearRect(0, 0, canvasWidth, canvasHeight);
scene.camera.x = 70*Math.sin(count);
scene.camera.y = 70;
scene.camera.z = 70*Math.cos(count);
scene.cameraRotation = count / 10;
count = 0.01;
scene.draw();
}
function load() {
// Init drawing system
canvas = document.getElementById("cv");
ctx = canvas.getContext("2d");
canvasWidth = canvas.width;
canvasHeight = canvas.height;
halfCanvasWidth = canvasWidth * 0.5;
halfCanvasHeight = canvasHeight * 0.5;
// Init 3D components
space = new Space();
scene = new Scene();
// Create a box shape and add it to the scene
scene.shapes['box'] = new Shape();
var p = scene.shapes['box'].points; // for convenience
p[0] = new Point(-10, -10, -10); // left bottom front
p[1] = new Point(10, -10, -10); // right bottom front
p[2] = new Point(10, 10, -10); // right top front
p[3] = new Point(-10, 10, -10); // left top front
p[4] = new Point(-10, -10, 10); // left bottom back
p[5] = new Point(10, -10, 10); // right bottom back
p[6] = new Point(10, 10, 10); // right top back
p[7] = new Point(-10, 10, 10); // left top back
// Back
scene.shapes['box'].polygons.push(new Polygon(
[ p[0], p[1], p[2], p[3] ],
new Point(0, 0, -1),
true /* double-sided */,
Polygon.SOLID,
[255, 0, 0]
));
// Front
scene.shapes['box'].polygons.push(new Polygon(
[ p[4], p[5], p[6], p[7] ],
new Point(0, 0, 1),
true /* double-sided */,
Polygon.SOLID,
[0, 0, 255]
));
// Top
scene.shapes['box'].polygons.push(new Polygon(
[ p[2], p[3], p[7], p[6] ],
new Point(0, 1, 0),
false /* single-sided */,
Polygon.WIRE,
[0, 255, 0]
));
// Transparent Top
scene.shapes['box'].polygons.push(new Polygon(
[ p[2], p[3], p[7], p[6] ],
new Point(0, 1, 0),
false /* single-sided */,
Polygon.SOLID,
[0, 255, 0, 0.4]
));
// Left
scene.shapes['box'].polygons.push(new Polygon(
[ p[0], p[4], p[7], p[3] ],
new Point(-1, 0, 0),
true /* double-sided */,
Polygon.SOLID,
[255, 255, 0]
));
// Right
scene.shapes['box'].polygons.push(new Polygon(
[ p[1], p[5], p[6], p[2] ],
new Point(1, 0, 0),
true /* double-sided */,
Polygon.SOLID,
[0, 255, 255]
));
// Create a floor shape and add it to the scene
scene.shapes['floor'] = new Shape();
var p = scene.shapes['floor'].points; // for convenience
p[0] = new Point(-40, -10, -40);
p[1] = new Point(-40, -10, 40);
p[2] = new Point( 40, -10, 40);
p[3] = new Point( 40, -10, -40);
// Floor
scene.shapes['floor'].polygons.push(new Polygon(
[ p[0], p[1], p[2], p[3] ],
new Point(0, 1, 0),
false /* single-sided */,
Polygon.SOLID,
[45, 45, 45]
));
setInterval('loop()', 20);
}
/* -------------------------------------------------------------------- */
</script>
<style>
body {
background-color:black;
margin:50px;
text-align:center;
}
</style>
</head>
<body onload="load();">
<canvas id="cv" width="400" height="300"></canvas>
</body>
</html>
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