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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 = 960, | |
| height = 960; | |
| var N = 1 << 0, | |
| S = 1 << 1, | |
| W = 1 << 2, | |
| E = 1 << 3; | |
| var cellSize = 4, | |
| cellSpacing = 4, | |
| cellWidth = Math.floor((width - cellSpacing) / (cellSize + cellSpacing)), | |
| cellHeight = Math.floor((height - cellSpacing) / (cellSize + cellSpacing)), | |
| marginLeft = Math.round((width - cellWidth * cellSize - (cellWidth + 1) * cellSpacing) / 2), | |
| marginTop = Math.round((height - cellHeight * cellSize - (cellHeight + 1) * cellSpacing) / 2), | |
| cells = generateMaze(cellWidth, cellHeight), // each cell’s edge bits | |
| parents = computeParents(cells, cellWidth, cellHeight), | |
| hoverIndex = cellWidth - 1; | |
| var canvas = d3.select("body").append("canvas") | |
| .attr("width", width) | |
| .attr("height", height) | |
| .on("ontouchstart" in document ? "touchmove" : "mousemove", mousemoved); | |
| var context = canvas.node().getContext("2d"); | |
| context.translate(marginLeft, marginTop); | |
| 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); | |
| } | |
| } | |
| context.fillStyle = "#f00"; | |
| fillPath(hoverIndex); | |
| function mousemoved() { | |
| var m = d3.mouse(this), | |
| x = Math.max(0, Math.min(cellWidth - 1, Math.floor((m[0] - marginLeft - cellSpacing) / (cellSize + cellSpacing)))), | |
| y = Math.max(0, Math.min(cellHeight - 1, Math.floor((m[1] - marginTop - cellSpacing) / (cellSize + cellSpacing)))); | |
| context.fillStyle = "#fff"; | |
| fillPath(hoverIndex); | |
| context.fillStyle = "#f00"; | |
| fillPath(hoverIndex = y * cellWidth + x); | |
| } | |
| function fillPath(i0) { | |
| var i1; | |
| while (true) { | |
| i1 = parents[i0]; | |
| fillCell(i0); | |
| if (i1 === i0 - 1) fillEast(i1); | |
| else if (i1 === i0 + 1) fillEast(i0); | |
| else if (i1 === i0 - cellWidth) fillSouth(i1); | |
| else if (i1 === i0 + cellWidth) fillSouth(i0); | |
| else break; | |
| i0 = 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 computeParents(cells, width, height) { | |
| var parents = new Array(width * height), | |
| i0 = (height - 1) * width, | |
| i1, | |
| frontier = [i0]; | |
| parents[i0] = i0; | |
| while ((i0 = frontier.pop()) != null) { | |
| if (cells[i0] & E && isNaN(parents[i1 = i0 + 1])) parents[i1] = i0, frontier.push(i1); | |
| if (cells[i0] & W && isNaN(parents[i1 = i0 - 1])) parents[i1] = i0, frontier.push(i1); | |
| if (cells[i0] & S && isNaN(parents[i1 = i0 + width])) parents[i1] = i0, frontier.push(i1); | |
| if (cells[i0] & N && isNaN(parents[i1 = i0 - width])) parents[i1] = i0, frontier.push(i1); | |
| } | |
| return parents; | |
| } | |
| function generateMaze(width, height) { | |
| var cells = new Array(width * height), // each cell’s edge bits | |
| remaining = d3.range(width * height), // cell indexes to visit | |
| previous = new Array(width * height); // current random walk | |
| // Add the starting cell. | |
| var start = remaining.pop(); | |
| cells[start] = 0; | |
| // While there are remaining cells, | |
| // add a loop-erased random walk to the maze. | |
| while (!loopErasedRandomWalk()); | |
| return cells; | |
| function loopErasedRandomWalk() { | |
| var i0, | |
| i1, | |
| x0, | |
| y0; | |
| // Pick a location that’s not yet in the maze (if any). | |
| do if ((i0 = remaining.pop()) == null) return true; | |
| while (cells[i0] >= 0); | |
| // Perform a random walk starting at this location, | |
| previous[i0] = i0; | |
| while (true) { | |
| x0 = i0 % width; | |
| y0 = i0 / width | 0; | |
| // picking a legal random direction at each step. | |
| i1 = Math.random() * 4 | 0; | |
| if (i1 === 0) { if (y0 <= 0) continue; --y0, i1 = i0 - width; } | |
| else if (i1 === 1) { if (y0 >= height - 1) continue; ++y0, i1 = i0 + width; } | |
| else if (i1 === 2) { if (x0 <= 0) continue; --x0, i1 = i0 - 1; } | |
| else { if (x0 >= width - 1) continue; ++x0, i1 = i0 + 1; } | |
| // If this new cell was visited previously during this walk, | |
| // erase the loop, rewinding the path to its earlier state. | |
| if (previous[i1] >= 0) eraseWalk(i0, i1); | |
| // Otherwise, just add it to the walk. | |
| else previous[i1] = i0; | |
| // If this cell is part of the maze, we’re done walking. | |
| if (cells[i1] >= 0) { | |
| // Add the random walk to the maze by backtracking to the starting cell. | |
| // Also erase this walk’s history to not interfere with subsequent walks. | |
| while ((i0 = previous[i1]) !== i1) { | |
| if (i1 === i0 + 1) cells[i0] |= E, cells[i1] |= W; | |
| else if (i1 === i0 - 1) cells[i0] |= W, cells[i1] |= E; | |
| else if (i1 === i0 + width) cells[i0] |= S, cells[i1] |= N; | |
| else cells[i0] |= N, cells[i1] |= S; | |
| previous[i1] = NaN; | |
| i1 = i0; | |
| } | |
| previous[i1] = NaN; | |
| return; | |
| } | |
| i0 = i1; | |
| } | |
| } | |
| function eraseWalk(i0, i2) { | |
| var i1; | |
| do i1 = previous[i0], previous[i0] = NaN, i0 = i1; while (i1 !== i2); | |
| } | |
| } | |
| d3.select(self.frameElement).style("height", height + "px"); | |
| </script> |
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