starfield.js

// based on: http://codentronix.com/2011/07/22/html5-canvas-3d-starfield/
var MAX_DEPTH = 32;

var canvas, ctx;
var stars = new Array(512);

var fs = require('fs');
var Canvas = require('canvas');
var Image = Canvas.Image;
var canvas = new Canvas(128, 16);
var panel = require('./index');
var mypanel;


if( canvas && canvas.getContext ) {
	ctx = canvas.getContext("2d");
	mypanel = new panel.Panel(ctx, 'ledpanel.lan', 1021);
	initStars();
	setInterval(loop,33);
}

/* Returns a random number in the range [minVal,maxVal] */
function randomRange(minVal,maxVal) {
	return Math.floor(Math.random() * (maxVal - minVal - 1)) + minVal;
}

function initStars() {
	for( var i = 0; i < stars.length; i++ ) {
		stars[i] = {
			x: randomRange(-25,25),
			y: randomRange(-25,25),
			z: randomRange(1,MAX_DEPTH)
		}
	}
}

function loop() {
	var halfWidth  = canvas.width / 2;
	var halfHeight = canvas.height / 2;

	ctx.fillStyle = "rgb(0,0,0)";
	ctx.fillRect(0,0,canvas.width,canvas.height);

	for( var i = 0; i < stars.length; i++ ) {
		stars[i].z -= 0.2;

		if( stars[i].z <= 0 ) {
			stars[i].x = randomRange(-25,25);
			stars[i].y = randomRange(-25,25);
			stars[i].z = MAX_DEPTH;
		}

		var k  = 10.0 / stars[i].z;
		var px = Math.round(stars[i].x * k + halfWidth);
		var py = Math.round(stars[i].y * k + halfHeight);

		if( px >= 0 && px <= 128 && py >= 0 && py <= 128 ) {
			var size = 1;//(1 - stars[i].z / 32.0) * 5;
			var shade = parseInt((1 - stars[i].z / 32.0) * 255);
			ctx.fillStyle = "rgb(0," +shade+"," + shade + ")";
			ctx.fillRect(px,py,size,size);
		}
	}
	mypanel.draw();
}