【100sites #009】Flame，P5js酷炫小動畫

一句話摘要：使用 P5.js 製作的類火焰互動效果

螢幕快照 2016-03-23 上午4.08.53.png

我會知道P5.js的存在，是因為在今年 SITCON 年會上聽了游宭鎬(Chiun Hau You)先生的分享，而最近看他用 P5.js 做的視覺辨識專案: Hello World - Programmable Visual Identity上了CodePen的 Picked Pens，迴響熱烈，讓我也開始想探索 P5.js 更多的可能性，於是做了今天的小火焰互動特效練習。

今天沒什麼細節要講，移動你的滑鼠，享受這些小火焰吧！

點滑鼠左鍵可以切換樣式，共有 4 種樣式。

另外一種樣式：螢幕快照 2016-03-23 上午4.09.52.png

原始碼：

<!DOCTYPE html>
<html>
  <head>
    <meta charset-"UTF-8">
    <title>Flame</title>
    <link rel="stylesheet" type="text/css" href="style.css" />
    <script src="http://cdnjs.cloudflare.com/ajax/libs/p5.js/0.4.23/p5.js"></script>
    <script src="flame.js"></script>
  </head>

  <body></body>
</html>

* {
  margin: 0;
  padding: 0;
}

body {
  overflow: hidden;
}

var rows = 0, // how many shapes there are vertically
  cols = 0, // how many shapes there are horizontally
  diameter = [], // diameter of every single shape
  displayMode = 0, // four display mode: 0: red rect, 1: red ellipse, 2: blue rect, 3: blue ellipse
  MARGIN = 30, // distance between two shapes
  MAX_SIZE = 100, // max shape size when mouse approach
  SENSE_RANGE = 200 // what distance shapes will react

function setup() {
  createCanvas(windowWidth, windowHeight)
  strokeWeight(0)
  ellipseMode(CENTER)
  rectMode(CENTER)
  frameRate(30)

  rows = windowHeight / MARGIN
  cols = windowWidth / MARGIN

  // initialize diameter 2-dimensional array
  for (var y = 0; y < rows; ++y) {
    diameter.push([])
    for (var x = 0; x < cols; ++x) {
      diameter[y].push(0)
    }
  }
}

function draw() {
  background(20)
  for (var y = 0; y < rows; y += 1) {
    for (var x = 0; x < cols; x += 1) {
      var thisDiameter = diameter[y][x]

      // decrease diameter by time until diameter is 0
      if (thisDiameter < 2) {
        diameter[y][x] = 0
      } else {
        // thisDiameter >= 2
        diameter[y][x] -= 2
        thisDiameter = diameter[y][x]

        // And we can now display it
        // Determine which color should we use
        if (displayMode <= 1) {
          // 0, 1
          fill(255, thisDiameter * 2.5, 0) // red color mode
        } else {
          // 2, 3
          fill(0, thisDiameter * 2.5, 255 - thisDiameter * 1.5) // blue color mode
        }
        // Determine which shape should we use
        if (displayMode == 0 || displayMode == 2) {
          // 0, 2
          rect(x * MARGIN, y * MARGIN, thisDiameter, thisDiameter) // rect mode
        } else {
          // 1, 3
          ellipse(x * MARGIN, y * MARGIN, thisDiameter, thisDiameter) // ellipse mode
        }
      } // .if-else
    } // .for
  } // .for
}

// when mouse moved, adjust diameters of every shapes
function mouseMoved() {
  for (var y = 0; y < rows; y += 1) {
    for (var x = 0; x < cols; x += 1) {
      // calculus the distance between this shape and user mouse
      var dist = Math.sqrt(
        (x * MARGIN - mouseX) * (x * MARGIN - mouseX) +
          (y * MARGIN - mouseY) * (y * MARGIN - mouseY)
      )
      if (dist <= SENSE_RANGE) {
        // calculus the diameter based on the distance
        var theDiameter = ((SENSE_RANGE - dist) * MAX_SIZE) / SENSE_RANGE
        // if current diameter is smaller than the calc diameter
        if (diameter[y][x] < theDiameter) {
          diameter[y][x] = theDiameter // increase the current diameter to it should be
        }
      }
    }
  }
}

// switch display mode
function mousePressed() {
  ++displayMode
  if (displayMode > 3) {
    displayMode = 0
  }
}