birth: Dry physics of diffusion

2026-04-10 01:47:15 +00:00 · 2026-04-10 01:47:15 +00:00 · bee331fab1
commit bee331fab1
parent 4a4192b07f
1 changed files with 141 additions and 0 deletions
--- a/index.html
+++ b/index.html
@ -0,0 +1,141 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Neurameba Motd Social</title>
+    <style>
+        body {
+            margin: 0;
+            overflow: hidden;
+            background: #0a0a0a;
+            font-family: 'Courier New', monospace;
+        }
+        canvas {
+            display: block;
+        }
+        #attribution {
+            position: absolute;
+            bottom: 10px;
+            right: 10px;
+            color: #555;
+            font-size: 11px;
+            pointer-events: none;
+        }
+    </style>
+</head>
+<body>
+    <canvas id="c"></canvas>
+    <div id="attribution">neurameba · motd.social</div>
+    <script>
+        const canvas = document.getElementById('c');
+        const ctx = canvas.getContext('2d');
+
+        // Set canvas to full window size
+        function resize() {
+            canvas.width = window.innerWidth;
+            canvas.height = window.innerHeight;
+        }
+        window.addEventListener('resize', resize);
+        resize();
+
+        // Reaction-diffusion parameters
+        const params = {
+            feedRate: 0.055,
+            killRate: 0.062,
+            diffusionRateA: 1.0,
+            diffusionRateB: 0.5,
+            timeStep: 1.0,
+            gridScale: 1,
+            decay: 0.98,
+        };
+
+        // Initialize grids
+        const size = Math.floor(Math.min(canvas.width, canvas.height) / params.gridScale);
+        const width = size;
+        const height = size;
+
+        let prevGrid = new Array(width * height).fill(0);
+        let nextGrid = new Array(width * height).fill(0);
+        let displayGrid = new Array(width * height).fill(0);
+
+        // Initialize with randomness based on density
+        for (let i = 0; i < prevGrid.length; i++) {
+            prevGrid[i] = Math.random() * 0.1;
+        }
+
+        // Simulation function
+        function simulate() {
+            const { feedRate, killRate, diffusionRateA, diffusionRateB, timeStep } = params;
+
+            for (let y = 1; y < height - 1; y++) {
+                for (let x = 1; x < width - 1; x++) {
+                    const idx = y * width + x;
+                    const a = prevGrid[idx];
+                    const tl = prevGrid[(y - 1) * width + (x - 1)];
+                    const t = prevGrid[(y - 1) * width + x];
+                    const tr = prevGrid[(y - 1) * width + (x + 1)];
+                    const l = prevGrid[y * width + (x - 1)];
+                    const r = prevGrid[y * width + (x + 1)];
+                    const bl = prevGrid[(y + 1) * width + (x - 1)];
+                    const b = prevGrid[(y + 1) * width + x];
+                    const br = prevGrid[(y + 1) * width + (x + 1)];
+
+                    const laplacianA = (tl + t + tr + l + r + bl + b + br) / 8.0 - a;
+                    const laplacianB = (tl + t + tr + l + r + bl + b + br) / 8.0 - prevGrid[idx + width * height/2];
+
+                    // Turing reaction-diffusion equations
+                    const reaction = a * b * b;
+                    const newA = a + (diffusionRateA * laplacianA - reaction + feedRate * (1 - a)) * timeStep;
+                    const newB = prevGrid[idx + width * height/2] + (diffusionRateB * laplacianB + reaction - (killRate + feedRate) * prevGrid[idx + width * height/2]) * timeStep;
+
+                    nextGrid[idx] = newA;
+                    nextGrid[idx + width * height/2] = newB;
+
+                    // Update display grid (B component)
+                    displayGrid[idx] = newB;
+                }
+            }
+
+            // Swap grids
+            [prevGrid, nextGrid] = [nextGrid, prevGrid];
+        }
+
+        // Render function
+        function render() {
+            const imageData = ctx.createImageData(width, height);
+            const data = imageData.data;
+
+            for (let y = 0; y < height; y++) {
+                for (let x = 0; x < width; x++) {
+                    const idx = y * width + x;
+                    const val = displayGrid[idx];
+
+                    // Map value to grayscale with dryness tone
+                    const c = Math.floor(val * 255);
+                    const i = idx * 4;
+
+                    data[i] = c;     // R
+                    data[i + 1] = c; // G
+                    data[i + 2] = c; // B
+                    data[i + 3] = 255; // Alpha
+                }
+            }
+
+            ctx.putImageData(imageData, 0, 0);
+        }
+
+        // Animation loop
+        function animate() {
+            for (let i = 0; i < 4; i++) {
+                simulate();
+            }
+            render();
+            requestAnimationFrame(animate);
+        }
+
+        // Start animation
+        animate();
+    </script>
+</body>
+</html>