Create doom_flame.js

src/programs/demos/doom_flame.js

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+/**
+@author ertdfgcvb
+@title  Doom Flame
+@desc   Oldschool flame effect
+[header]
+*/
+
+import { clamp, map } from '/src/modules/num.js'
+import { CSS4 } from '/src/modules/colors.js'
+import { lerp, smoothstep } from '/src/modules/num.js'
+
+
+export const settings = { background : 'black' }
+
+const { min, max, sin, floor } = Math
+
+
+const palette = [
+	CSS4.black,         // 0
+	CSS4.purple,        // 1
+	CSS4.darkred,       // 2
+	CSS4.red,           // 3
+	CSS4.orangered,     // 4
+	CSS4.gold,          // 5
+	CSS4.lemonchiffon,  // 6
+	CSS4.white          // 7
+]
+
+const flame = '011222233334444444455566667'.split('').map(e=>parseInt(e))
+
+const noise = valueNoise()
+
+let cols, rows
+
+export function pre(context, cursor, buffers){
+
+	const buf = buffers.data
+
+	if (cols != context.cols || rows != context.rows) {
+		cols = context.cols
+		rows = context.rows
+		const tot = cols * rows
+		for (let i=0; i<tot; i++) {
+			buf[i] = 0
+		}
+	}
+
+	// Floor flame:
+	if (!cursor.pressed) {
+		const t = context.time * 0.0015
+		const last = cols * (rows - 1)
+		for (let i=0; i<cols; i++) {
+			const val = floor(map(noise(i * 0.05, t), 0, 1, 5, 50))
+			buf[last + i] = min(val, buf[last + i] + 2)
+		}
+	} else {
+		const cx = floor(cursor.x)
+		const cy = floor(cursor.y)
+		buf[cx + cy * cols] = rndi(5, 50)
+	}
+
+	for (let i=0; i<buf.length; i++) {
+		const row = floor(i / cols)
+		const col = i % cols
+  		const dest = row * cols + clamp(col + rndi(-1, 1), 0, cols-1)
+  		const src = min(rows-1, row + 1) * cols + col
+  		buf[dest] = max(0, buf[src]-rndi(0, 2))
+	}
+
+}
+
+export function main(coord, context, cursor, buffers){
+
+	const idx = coord.y * context.cols + coord.x
+	const u = buffers.data[idx]
+	const v = flame[clamp(u, 0, flame.length-1)]
+
+	if (v === 0) return
+
+	return {
+		char : u % 10,
+		color : palette[min(palette.length-1,v+1)].hex,
+		background : palette[v].hex
+	}
+}
+
+// Random int betweem a and b, inclusive!
+function rndi(a, b=0) {
+	if (a > b) [a, b] = [b, a]
+	return Math.floor(a + Math.random() * (b - a + 1))
+}
+
+
+// Value noise:
+// https://www.scratchapixel.com/lessons/procedural-generation-virtual-worlds/procedural-patterns-noise-part-1
+function valueNoise() {
+
+	const tableSize = 256;
+	const r = new Array(tableSize)
+	const permutationTable = new Array(tableSize * 2)
+
+    // Create an array of random values and initialize permutation table
+    for (let k=0; k<tableSize; k++) {
+        r[k] = Math.random()
+        permutationTable[k] = k
+    }
+
+    // Shuffle values of the permutation table
+    for (let k=0; k<tableSize; k++) {
+        const i = Math.floor(Math.random() * tableSize)
+        // swap
+        ;[permutationTable[k], permutationTable[i]] = [permutationTable[i], permutationTable[k]]
+        permutationTable[k + tableSize] = permutationTable[k]
+    }
+
+    return function(px, py) {
+	    const xi = Math.floor(px)
+	    const yi = Math.floor(py)
+
+	    const tx = px - xi
+	    const ty = py - yi
+
+	    const rx0 = xi % tableSize
+	    const rx1 = (rx0 + 1) % tableSize
+	    const ry0 = yi % tableSize
+	    const ry1 = (ry0 + 1) % tableSize
+
+	    // random values at the corners of the cell using permutation table
+	    const c00 = r[permutationTable[permutationTable[rx0] + ry0]]
+	    const c10 = r[permutationTable[permutationTable[rx1] + ry0]]
+	    const c01 = r[permutationTable[permutationTable[rx0] + ry1]]
+	    const c11 = r[permutationTable[permutationTable[rx1] + ry1]]
+
+	    // remapping of tx and ty using the Smoothstep function
+	    const sx = smoothstep(0, 1, tx);
+	    const sy = smoothstep(0, 1, ty);
+
+	    // linearly interpolate values along the x axis
+	    const nx0 = lerp(c00, c10, sx)
+	    const nx1 = lerp(c01, c11, sx)
+
+	    // linearly interpolate the nx0/nx1 along they y axis
+	    return lerp(nx0, nx1, sy)
+	}
+}
+
+
+import { drawInfo } from '/src/modules/drawbox.js'
+export function post(context, cursor, buffers){
+	drawInfo(context, cursor, buffers)
+}