engine.scope(({ start, cls, rectfill, pset, line, btn, caption }) => { const map = [ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1], [1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1], [1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1], ]; const mapSize = 16; const sprites = { wall: [ 6, 6, 6, 5, 6, 6, 6, 6, 6, 6, 6, 5, 6, 6, 6, 6, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 5, 6, 6, 6, 6, 6, 6, 6, 5, 6, 6, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 5, 6, 6, 6, 6, 6, 6, 6, 5, 6, 6, 6, 6, ], }; const darken = [ 0, 0, 0, 0, 2, 0, 5, 6, 2, 4, 9, 3, 1, 1, 2, 9, ]; const bayer = [ 0 / 16, 8 / 16, 2 / 16, 10 / 16, 12 / 16, 4 / 16, 14 / 16, 6 / 16, 3 / 16, 11 / 16, 1 / 16, 9 / 16, 15 / 16, 7 / 16, 13 / 16, 5 / 16, ]; const FOG_START = 3; const MAX_DIST = 6; let px = 2.5; let py = 2.5; let pa = 0; const fov = 0.66; const moveSpeed = 0.05; const rotSpeed = 0.05; const cell = 2; const mapW = mapSize * cell; const mmX = 128 - mapW; const mmY = 128 - mapW; const viewW = 128; const viewH = 128; function update() { if (btn('ArrowLeft')) pa -= rotSpeed; if (btn('ArrowRight')) pa += rotSpeed; if (btn('ArrowUp')) { const nx = px + Math.cos(pa) * moveSpeed; const ny = py + Math.sin(pa) * moveSpeed; if (map[Math.floor(py)][Math.floor(nx)] === 0) px = nx; if (map[Math.floor(ny)][Math.floor(px)] === 0) py = ny; } if (btn('ArrowDown')) { const nx = px - Math.cos(pa) * moveSpeed; const ny = py - Math.sin(pa) * moveSpeed; if (map[Math.floor(py)][Math.floor(nx)] === 0) px = nx; if (map[Math.floor(ny)][Math.floor(px)] === 0) py = ny; } } function fogAmount(dist) { if (dist <= FOG_START) return 0; return Math.min(1, (dist - FOG_START) / (MAX_DIST - FOG_START)); } function applyFog(color, fogFactor, sx, sy) { const threshold = bayer[(sy % 4) * 4 + (sx % 4)]; if (fogFactor > threshold + 0.5) { return darken[darken[color]]; } else if (fogFactor > threshold) { return darken[color]; } return color; } function draw() { cls(0); const halfH = viewH / 2; for (let sy = 0; sy < viewH; sy++) { const distFromHorizon = Math.abs(sy - halfH); const floorFog = 1 - distFromHorizon / halfH; const baseColor = sy < halfH ? 1 : 5; for (let sx = 0; sx < viewW; sx++) { pset(sx, sy, applyFog(baseColor, floorFog, sx, sy)); } } const dirX = Math.cos(pa); const dirY = Math.sin(pa); const planeX = -dirY * fov; const planeY = dirX * fov; for (let x = 0; x < viewW; x++) { const cameraX = (2 * x) / viewW - 1; const rdx = dirX + planeX * cameraX; const rdy = dirY + planeY * cameraX; let mapX = Math.floor(px); let mapY = Math.floor(py); const deltaDistX = Math.abs(rdx) < 1e-10 ? 1e30 : Math.abs(1 / rdx); const deltaDistY = Math.abs(rdy) < 1e-10 ? 1e30 : Math.abs(1 / rdy); let stepX, stepY, sideDistX, sideDistY; if (rdx < 0) { stepX = -1; sideDistX = (px - mapX) * deltaDistX; } else { stepX = 1; sideDistX = (mapX + 1 - px) * deltaDistX; } if (rdy < 0) { stepY = -1; sideDistY = (py - mapY) * deltaDistY; } else { stepY = 1; sideDistY = (mapY + 1 - py) * deltaDistY; } let side; while (true) { if (sideDistX < sideDistY) { sideDistX += deltaDistX; mapX += stepX; side = 0; } else { sideDistY += deltaDistY; mapY += stepY; side = 1; } if (map[mapY]?.[mapX] === 1) break; } const perpDist = side === 0 ? sideDistX - deltaDistX : sideDistY - deltaDistY; const fogFactor = fogAmount(perpDist); const stripeH = Math.floor(viewH / perpDist); const drawStart = Math.max( 0, Math.floor(viewH / 2 - stripeH / 2), ); const drawEnd = Math.min( viewH, Math.floor(viewH / 2 + stripeH / 2), ); let wallHit; if (side === 0) { wallHit = py + perpDist * rdy; } else { wallHit = px + perpDist * rdx; } wallHit -= Math.floor(wallHit); const tx = Math.floor(wallHit * 8); const texStep = 8 / stripeH; let texPos = (drawStart - viewH / 2 + stripeH / 2) * texStep; for (let sy = drawStart; sy < drawEnd; sy++) { const ty = Math.min(7, Math.floor(texPos)); texPos += texStep; let color = sprites.wall[ty * 8 + tx]; if (color < 0) continue; if (side === 0) { color = darken[color]; } color = applyFog(color, fogFactor, x, sy); pset(x, sy, color); } } for (let y = 0; y < mapSize; y++) { for (let x = 0; x < mapSize; x++) { const color = map[y][x] === 1 ? 5 : 6; rectfill( mmX + x * cell, mmY + y * cell, mmX + (x + 1) * cell, mmY + (y + 1) * cell, color, ); } } const dirX2 = Math.cos(pa); const dirY2 = Math.sin(pa); const planeX2 = -dirY2 * fov; const planeY2 = dirX2 * fov; for (let x = 0; x < viewW; x += 8) { const cameraX = (2 * x) / viewW - 1; const rdx = dirX2 + planeX2 * cameraX; const rdy = dirY2 + planeY2 * cameraX; let mX = Math.floor(px); let mY = Math.floor(py); const ddx = Math.abs(rdx) < 1e-10 ? 1e30 : Math.abs(1 / rdx); const ddy = Math.abs(rdy) < 1e-10 ? 1e30 : Math.abs(1 / rdy); let sX, sY, sdx, sdy; if (rdx < 0) { sX = -1; sdx = (px - mX) * ddx; } else { sX = 1; sdx = (mX + 1 - px) * ddx; } if (rdy < 0) { sY = -1; sdy = (py - mY) * ddy; } else { sY = 1; sdy = (mY + 1 - py) * ddy; } let sd; while (true) { if (sdx < sdy) { sdx += ddx; mX += sX; sd = 0; } else { sdy += ddy; mY += sY; sd = 1; } if (map[mY]?.[mX] === 1) break; } const pd = sd === 0 ? sdx - ddx : sdy - ddy; const hx = px + rdx * pd; const hy = py + rdy * pd; line( mmX + Math.floor(px * cell), mmY + Math.floor(py * cell), mmX + Math.floor(hx * cell), mmY + Math.floor(hy * cell), 10, ); } rectfill( mmX + Math.floor(px * cell) - 1, mmY + Math.floor(py * cell) - 1, mmX + Math.floor(px * cell) + 2, mmY + Math.floor(py * cell) + 2, 8, ); line( mmX + Math.floor(px * cell), mmY + Math.floor(py * cell), mmX + Math.floor(px * cell + Math.cos(pa) * 4), mmY + Math.floor(py * cell + Math.sin(pa) * 4), 8, ); caption('smooth fog via dithering', 2, 2, 7); } start({ sprites, sounds: {}, update, draw, target }); });

Editing: Fog & Lighting: Dithered Fog

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