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maze.html
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<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
background: #000;
}
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script>
var width = 9600, // 960
height = 9600; //960
var N = 1 << 0,
S = 1 << 1,
W = 1 << 2,
E = 1 << 3;
var cellSize = 120, // 4
cellSpacing = 4,
cellWidth = Math.floor((width - cellSpacing) / (cellSize + cellSpacing)),
cellHeight = Math.floor((height - cellSpacing) / (cellSize + cellSpacing)),
cells = generateMaze(cellWidth, cellHeight), // each cell’s edge bits
distance = d3.range(cellWidth * cellHeight).map(function() { return 0; }),
frontier = [(cellHeight - 1) * cellWidth];
var canvas = d3.select("body").append("canvas")
.attr("width", width)
.attr("height", height);
var context = canvas.node().getContext("2d");
context.translate(
Math.round((width - cellWidth * cellSize - (cellWidth + 1) * cellSpacing) / 2),
Math.round((height - cellHeight * cellSize - (cellHeight + 1) * cellSpacing) / 2)
);
context.fillStyle = "#fff";
for (var y = 0, i = 0; y < cellHeight; ++y) {
for (var x = 0; x < cellWidth; ++x, ++i) {
fillCell(i);
if (cells[i] & S) fillSouth(i);
if (cells[i] & E) fillEast(i);
}
}
d3.timer(function() {
for (var i = 0; i < 50; ++i) {
if (exploreFrontier()) {
return true;
}
}
});
function exploreFrontier() {
if ((i0 = popRandom(frontier)) == null) return true;
var i0,
i1,
d0 = distance[i0],
d1 = d0 + 1;
context.fillStyle = d3.hsl(d0 % 360, 1, .5) + "";
fillCell(i0);
context.fillStyle = d3.hsl(d1 % 360, 1, .5) + "";
if (cells[i0] & E && !distance[i1 = i0 + 1]) distance[i1] = d1, fillEast(i0), frontier.push(i1);
if (cells[i0] & W && !distance[i1 = i0 - 1]) distance[i1] = d1, fillEast(i1), frontier.push(i1);
if (cells[i0] & S && !distance[i1 = i0 + cellWidth]) distance[i1] = d1, fillSouth(i0), frontier.push(i1);
if (cells[i0] & N && !distance[i1 = i0 - cellWidth]) distance[i1] = d1, fillSouth(i1), frontier.push(i1);
}
function fillCell(i) {
var x = i % cellWidth, y = i / cellWidth | 0;
context.fillRect(x * cellSize + (x + 1) * cellSpacing, y * cellSize + (y + 1) * cellSpacing, cellSize, cellSize);
}
function fillEast(i) {
var x = i % cellWidth, y = i / cellWidth | 0;
context.fillRect((x + 1) * (cellSize + cellSpacing), y * cellSize + (y + 1) * cellSpacing, cellSpacing, cellSize);
}
function fillSouth(i) {
var x = i % cellWidth, y = i / cellWidth | 0;
context.fillRect(x * cellSize + (x + 1) * cellSpacing, (y + 1) * (cellSize + cellSpacing), cellSize, cellSpacing);
}
function generateMaze(width, height) {
var cells = new Array(cellWidth * cellHeight), // each cell’s edge bits
frontier = [];
var start = (cellHeight - 1) * cellWidth;
cells[start] = 0;
frontier.push({index: start, direction: N});
frontier.push({index: start, direction: E});
shuffle(frontier, 0, 2);
while (!exploreFrontier());
return cells;
function exploreFrontier() {
if ((edge = frontier.pop()) == null) return true;
var edge,
i0 = edge.index,
d0 = edge.direction,
i1 = i0 + (d0 === N ? -cellWidth : d0 === S ? cellWidth : d0 === W ? -1 : +1),
x0 = i0 % cellWidth,
y0 = i0 / cellWidth | 0,
x1,
y1,
d1,
open = cells[i1] == null; // opposite not yet part of the maze
if (d0 === N) x1 = x0, y1 = y0 - 1, d1 = S;
else if (d0 === S) x1 = x0, y1 = y0 + 1, d1 = N;
else if (d0 === W) x1 = x0 - 1, y1 = y0, d1 = E;
else x1 = x0 + 1, y1 = y0, d1 = W;
if (open) {
cells[i0] |= d0, cells[i1] |= d1;
var m = 0;
if (y1 > 0 && cells[i1 - cellWidth] == null) frontier.push({index: i1, direction: N}), ++m;
if (y1 < cellHeight - 1 && cells[i1 + cellWidth] == null) frontier.push({index: i1, direction: S}), ++m;
if (x1 > 0 && cells[i1 - 1] == null) frontier.push({index: i1, direction: W}), ++m;
if (x1 < cellWidth - 1 && cells[i1 + 1] == null) frontier.push({index: i1, direction: E}), ++m;
shuffle(frontier, frontier.length - m, frontier.length);
}
}
}
function popRandom(array) {
if (!array.length) return;
var n = array.length, i = Math.random() * n | 0, t;
t = array[i], array[i] = array[n - 1], array[n - 1] = t;
return array.pop();
}
function shuffle(array, i0, i1) {
var m = i1 - i0, t, i, j;
while (m) {
i = Math.random() * m-- | 0;
t = array[m + i0], array[m + i0] = array[i + i0], array[i + i0] = t;
}
return array;
}
d3.select(self.frameElement).style("height", height + "px");
</script>