This is some exploration of Rhodonea curves (a.k.a rose curves). Also see what Jason Davies did here.
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June 29, 2017 22:57
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Rhodonea Curve
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| license: mit |
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| <!DOCTYPE html> | |
| <title>Rhodonea Curve</title> | |
| <style> | |
| body { | |
| font-family: Monospace; | |
| margin:0px; | |
| } | |
| canvas { | |
| position: absolute; | |
| top: 0px; | |
| left: 0px; | |
| z-index: -2; | |
| } | |
| .controls { | |
| background-color: rgba(255, 255, 255, .75); | |
| box-shadow: 0px 0px 5px rgb(200, 200, 200); | |
| margin: 5px; | |
| padding: 10px; | |
| z-index: 9; | |
| display: inline-block; | |
| } | |
| </style> | |
| <div class="controls"> | |
| <div class="a"> | |
| <div class="aText">a: </div> | |
| <input type="range" min="1" max="20" name="a" oninput="updateRange(this)"> | |
| </div> | |
| <div class="b"> | |
| <div class="bText">b: </div> | |
| <input type="range" min="1" max="20" name="b" oninput="updateRange(this)"> | |
| </div> | |
| </div> | |
| <canvas></canvas> | |
| <script> | |
| const canvas = document.querySelector('canvas'); | |
| canvas.setAttribute('width',innerWidth); | |
| canvas.setAttribute('height',innerHeight); | |
| const canvasCtx = canvas.getContext("2d"); | |
| canvasCtx.fillStyle = 'rgb(255, 255, 255)'; | |
| canvasCtx.strokeStyle = 'rgb(255, 0, 0)'; | |
| canvasCtx.lineWidth = 1; | |
| const length = 7200; | |
| let t = 1; | |
| const state = { | |
| a: Math.ceil(Math.random() * 20), | |
| b: Math.ceil(Math.random() * 20), | |
| oldA: 0, | |
| oldB: 0, | |
| } | |
| // make sure a and b are different | |
| state.b = state.b === state.a ? Math.ceil(Math.random() * 20) : state.b; | |
| document.querySelector("input[name=a]").value = state.a; | |
| document.querySelector("input[name=b]").value = state.b; | |
| const aText = document.querySelector(".aText"); | |
| const bText = document.querySelector(".bText"); | |
| aText.innerHTML = "a: " + state.a; | |
| bText.innerHTML = "b: " + state.b; | |
| update(); | |
| function updateRange(input) { | |
| state[input.name] = Number(input.value); | |
| if (input.name === "a") aText.innerHTML = "a: " + state.a; | |
| else bText.innerHTML = "b: " + state.b; | |
| if (t >= 1) { | |
| t = 0; | |
| update(); | |
| } else { | |
| [state.oldA, state.oldB] = [state.a, state.b]; | |
| } | |
| } | |
| function update() { | |
| canvasCtx.fillRect(0, 0, innerWidth, innerHeight); | |
| t = t >= 1 ? 1 : t + .05; | |
| if (t === 1) [state.oldA, state.oldB] = [state.a, state.b]; | |
| else requestAnimationFrame(update); | |
| canvasCtx.beginPath(); | |
| let i = length; | |
| while (i--) { | |
| const oldX = getVal(state.oldA, i, "sin") + getVal(state.oldB, i, "sin"); | |
| const oldY = getVal(state.oldA, i, "cos") + getVal(state.oldB, i, "cos"); | |
| const x = getVal(state.a, i, "sin") + getVal(state.b, i, "sin"); | |
| const y = getVal(state.a, i, "cos") + getVal(state.b, i, "cos"); | |
| canvasCtx.lineTo(tween(oldX, x) + innerWidth/2, tween(oldY, y) + innerHeight/2); | |
| } | |
| canvasCtx.stroke(); | |
| } | |
| function getVal(val, n, func) { | |
| return Math[func](2 * Math.PI * val * n / length) * Math.min(innerWidth, innerHeight) / 5; | |
| } | |
| function tween(oldVal, newVal) { | |
| return oldVal * (1 - t) + newVal * t; | |
| } | |
| </script> |
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