viz7
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Brian Picciano
parent
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src/_posts/2021-07-01-viz-7.md
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440
src/_posts/2021-07-01-viz-7.md
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---
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title: >-
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Visualization 7
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description: >-
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Feedback Loop.
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series: viz
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tags: tech art
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---
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<script type="text/javascript">
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function randn(n) {
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return Math.floor(Math.random() * n);
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}
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const w = 100;
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const h = 60;
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class Canvas {
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constructor(canvasDOM) {
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this.dom = canvasDOM;
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this.ctx = canvasDOM.getContext("2d");
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// expand canvas element's width to match parent.
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this.dom.width = this.dom.parentElement.offsetWidth;
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// rectSize must be an even number or the pixels don't display nicely.
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this.rectSize = Math.floor(this.dom.width / w /2) * 2;
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this.dom.width = w * this.rectSize;
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this.dom.height = h * this.rectSize;
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}
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rectSize() {
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return Math.floor(this.dom.width / w);
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}
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}
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class UniverseState {
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constructor(layers) {
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this.tick = 0;
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this.layers = layers;
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}
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neighboringLayers(layerIndex) {
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const prevIndex = layerIndex-1;
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const prev = prevIndex < 0 ? null : this.layers[prevIndex];
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const nextIndex = layerIndex+1;
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const next = nextIndex >= this.layers.length ? null : this.layers[nextIndex];
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return [prev, next];
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}
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}
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const defaultKnobs = {
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maxNewElsPerTick: 10,
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ageOfDeath: 30,
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drift: 30,
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neighborScalar: 0,
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prevLayerScalar: 0,
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prevLayerLikenessScalar: 0,
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nextLayerScalar: 0,
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nextLayerLikenessScalar: 0,
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chaos: 0,
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};
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class Layer {
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constructor(className, newEl, knobs = {}) {
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this.className = className;
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this.els = {};
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this.diff = {};
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this.newEl = newEl;
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this.knobs = { ...defaultKnobs, ...knobs };
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}
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_normCoord(coord) {
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if (typeof coord !== 'string') coord = JSON.stringify(coord);
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return coord;
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}
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get(coord) {
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return this.els[this._normCoord(coord)];
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}
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getAll() {
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return Object.values(this.els);
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}
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set(coord, el) {
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this.diff[this._normCoord(coord)] = {action: "set", coord: coord, ...el};
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}
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unset(coord) {
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this.diff[this._normCoord(coord)] = {action: "unset"};
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}
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applyDiff() {
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for (const coordStr in this.diff) {
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const el = this.diff[coordStr];
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delete this.diff[coordStr];
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if (el.action == "set") {
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delete el.action;
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this.els[coordStr] = el;
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} else {
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delete this.els[coordStr];
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}
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}
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}
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update(state, thisLayerIndex) {
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// Apply diff from previous update first. The diff can't be applied last
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// because it needs to be present during the draw phase.
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this.applyDiff();
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const allEls = this.getAll().sort(() => Math.random() - 0.5);
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if (allEls.length == 0) {
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const newEl = this.newEl(this, [])
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newEl.tick = state.tick;
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this.set([w/2, h/2], newEl);
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return;
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}
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let newEls = 0;
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for (const el of allEls) {
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const nCoord = randEmptyNeighboringCoord(this, el.coord);
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if (!nCoord) continue; // el has no empty neighboring spots
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const newEl = this.newEl(this, neighboringElsOf(this, nCoord))
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newEl.tick = state.tick;
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this.set(nCoord, newEl);
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newEls++;
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if (newEls >= this.knobs.maxNewElsPerTick) break;
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}
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const calcLayerBonus = (el, layer, scalar, likenessScalar) => {
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if (!layer) return 0;
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const nEls = neighboringElsOf(layer, el.coord, true)
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const likeness = nEls.reduce((likeness, nEl) => {
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const diff = Math.abs(nEl.c - el.c);
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return likeness + Math.max(diff, Math.abs(1 - diff));
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}, 0);
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return (nEls.length * scalar) + (likeness * likenessScalar);
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};
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const [prevLayer, nextLayer] = state.neighboringLayers(thisLayerIndex);
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for (const el of allEls) {
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const age = state.tick - el.tick;
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const neighborBonus = neighboringElsOf(this, el.coord).length * this.knobs.neighborScalar;
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const prevLayerBonus = calcLayerBonus(el, prevLayer, this.knobs.prevLayerScalar, this.knobs.prevLayerLikenessScalar);
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const nextLayerBonus = calcLayerBonus(el, nextLayer, this.knobs.nextLayerScalar, this.knobs.nextLayerLikenessScalar);
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const chaos = (this.chaos > 0) ? randn(this.knobs.chaos) : 0;
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if (age - neighborBonus - prevLayerBonus - nextLayerBonus + chaos >= this.knobs.ageOfDeath) {
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this.unset(el.coord);
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}
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}
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}
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draw(canvas) {
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for (const coordStr in this.diff) {
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const el = this.diff[coordStr];
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const coord = JSON.parse(coordStr);
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if (el.action == "set") {
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canvas.ctx.fillStyle = `hsl(${el.h}, ${el.s}, ${el.l})`;
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canvas.ctx.fillRect(
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coord[0]*canvas.rectSize, coord[1]*canvas.rectSize,
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canvas.rectSize, canvas.rectSize,
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);
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} else {
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canvas.ctx.clearRect(
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coord[0]*canvas.rectSize, coord[1]*canvas.rectSize,
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canvas.rectSize, canvas.rectSize,
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);
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}
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}
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}
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}
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const neighbors = [
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[-1, -1], [0, -1], [1, -1],
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[-1, 0], /* [0, 0], */ [1, 0],
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[-1, 1], [0, 1], [1, 1],
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];
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function neighborsOf(coord) {
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return neighbors.map((n) => {
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let nX = coord[0]+n[0];
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let nY = coord[1]+n[1];
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nX = (nX + w) % w;
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nY = (nY + h) % h;
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return [nX, nY];
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});
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}
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function randEmptyNeighboringCoord(layer, coord) {
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const neighbors = neighborsOf(coord).sort(() => Math.random() - 0.5);
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for (const nCoord of neighbors) {
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if (!layer.get(nCoord)) return nCoord;
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}
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return null;
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}
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function neighboringElsOf(layer, coord, includeCoord = false) {
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const neighboringEls = [];
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const neighboringCoords = neighborsOf(coord);
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if (includeCoord) neighboringCoords.push(coord);
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for (const nCoord of neighboringCoords) {
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const el = layer.get(nCoord);
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if (el) neighboringEls.push(el);
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}
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return neighboringEls;
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}
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function newEl(h, l) {
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return {
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h: h,
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s: "100%",
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l: l,
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c: h / 360, // c is used to compare the element to others
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};
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}
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function mkNewEl(l) {
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return (layer, nEls) => {
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const s = "100%";
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if (nEls.length == 0) {
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const h = randn(360);
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return newEl(h, l);
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}
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// for each h (which can be considered as degrees around a circle) break the
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// h down into x and y vectors, and add those up separately. Then find the
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// angle between those two resulting vectors, and that's the "average" h
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// value.
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let x = 0;
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let y = 0;
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nEls.forEach((el) => {
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const hRad = el.h * Math.PI / 180;
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x += Math.cos(hRad);
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y += Math.sin(hRad);
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});
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let h = Math.atan2(y, x);
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h = h / Math.PI * 180;
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// apply some random drift, normalize
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h += (Math.random() * layer.knobs.drift * 2) - layer.knobs.drift;
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h = (h + 360) % 360;
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return newEl(h, l);
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}
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}
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class Universe {
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constructor(canvasesByClass, layers) {
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this.canvasesByClass = canvasesByClass;
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this.state = new UniverseState(layers);
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}
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update() {
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this.state.tick++;
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let prevLayer;
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this.state.layers.forEach((layer, i) => {
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layer.update(this.state, i);
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prevLayer = layer;
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});
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}
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draw() {
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this.state.layers.forEach((layer) => {
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if (!this.canvasesByClass[layer.className]) return;
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this.canvasesByClass[layer.className].forEach((canvas) => {
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layer.draw(canvas);
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});
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});
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}
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}
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</script>
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<style>
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.canvasContainer {
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display: grid;
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margin-bottom: 2rem;
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text-align: center;
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}
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canvas {
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border: 1px dashed #AAA;
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width: 100%;
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grid-area: 1/1/2/2;
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}
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</style>
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<div class="canvasContainer">
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<canvas class="layer1"></canvas>
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<canvas class="layer2"></canvas>
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</div>
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<div class="row">
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<div class="columns six">
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<h3>Bottom Layer</h3>
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<div class="canvasContainer"><canvas class="layer1"></canvas></div>
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<div class="layer1 layerParams">
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<label>Max New Elements Per Tick</label><input type="text" param="maxNewElsPerTick" />
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<label>Color Drift</label><input type="text" param="drift" />
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<label>Age of Death</label><input type="text" param="ageOfDeath" />
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<label>Neighbor Scalar</label><input type="text" param="neighborScalar" />
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<label>Top Layer Neighbor Scalar</label><input type="text" param="nextLayerScalar" />
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<label>Top Layer Neighbor Likeness Scalar</label><input type="text" param="nextLayerLikenessScalar" />
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</div>
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</div>
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<div class="columns six">
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<h3>Top Layer</h3>
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<div class="canvasContainer"><canvas class="layer2"></canvas></div>
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<div class="layer2 layerParams">
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<label>Max New Elements Per Tick</label><input type="text" param="maxNewElsPerTick" />
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<label>Color Drift</label><input type="text" param="drift" />
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<label>Age of Death</label><input type="text" param="ageOfDeath" />
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<label>Neighbor Scalar</label><input type="text" param="neighborScalar" />
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<label>Bottom Layer Neighbor Scalar</label><input type="text" param="prevLayerScalar" />
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<label>Bottom Layer Neighbor Likeness Scalar</label><input type="text" param="prevLayerLikenessScalar" />
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</div>
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</div>
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</div>
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Once again, this visualization iterates upon the previous. In the last one the
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top layer was able to "see" the bottom, and was therefore able to bolster or
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penalize its own elements which were on or near bottom layer elements, but not
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vice-versa. This time both layers can see each other, and the "Layer Neighbor
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Scalar" can be used to adjust lifetime of elements which are on/near elements of
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the neighboring layer.
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By default, the bottom layer has a high affinity to the top, and the top layer
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has a some (but not as much) affinity in return.
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Another addition is the "likeness" scalar. Likeness is defined as the degree to
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which one element is like another. In this visualization likeness is determined
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by color. The "Layer Neighbor Likeness Scalar" adjusts the lifetime of elements
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based on how like they are to nearby elements on the neighboring layer.
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By default, the top layer has a high affinity for the bottom's color, but the
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bottom doesn't care about the top's color at all (and so its color will drift
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aimlessly).
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And finally "Color Drift" can be used to adjust the degree to which the color of
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new elements can diverge from its parents. This has always been hardcoded, but
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can now be adjusted separately across the different layers.
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In the default configuration the top layer will (eventually) converge to roughly
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match the bottom both in shape and color. When I first implemented the likeness
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scaling I thought it was broken, because the top would never converge to the
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bottom's color.
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What I eventually realized was that the top must have a higher color drift than
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the bottom in order for it to do so, otherwise the top would always be playing
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catchup. However, if the drift difference is _too_ high then the top layer
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becomes chaos and also doesn't really follow the color of the bottom. A
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difference of 10 (degrees out of 360) is seemingly enough.
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<script>
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const canvasesByClass = {};
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[...document.getElementsByTagName("canvas")].forEach((canvasDOM) => {
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const canvas = new Canvas(canvasDOM);
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canvasDOM.classList.forEach((name) => {
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if (!canvasesByClass[name]) canvasesByClass[name] = [];
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canvasesByClass[name].push(canvas);
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})
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});
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const layers = [
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new Layer("layer1", mkNewEl("90%"), {
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maxNewElsPerTick: 2,
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ageOfDeath: 30,
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drift: 40,
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neighborScalar: 50,
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nextLayerScalar: 20,
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}),
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new Layer("layer2", mkNewEl("50%", ), {
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maxNewElsPerTick: 15,
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ageOfDeath: 1,
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drift: 50,
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neighborScalar: 5,
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prevLayerScalar: 5,
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prevLayerLikenessScalar: 20,
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}),
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];
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for (const layer of layers) {
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document.querySelectorAll(`.${layer.className}.layerParams > input`).forEach((input) => {
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const param = input.getAttribute("param");
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// pre-fill input values
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input.value = layer.knobs[param];
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input.onchange = () => {
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console.log(`setting ${layer.className}.${param} to ${input.value}`);
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layer.knobs[param] = input.value;
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};
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});
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}
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const universe = new Universe(canvasesByClass, layers);
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const requestAnimationFrame =
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window.requestAnimationFrame ||
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window.mozRequestAnimationFrame ||
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window.webkitRequestAnimationFrame ||
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window.msRequestAnimationFrame;
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function doTick() {
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universe.update();
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universe.draw();
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requestAnimationFrame(doTick);
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}
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doTick();
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</script>
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