feat: cumulus

app/level.ts

@@ -1,6 +1,6 @@
 import { Color } from "../engine/render/Color"
 import type { SkyConfig } from "../engine/render/Sky"
-import type { Mesh, Vertex } from "../engine/scene/Mesh"
+import type { Mesh } from "../engine/scene/Mesh"
 
 type Corner = [number, number, number]
 
@@ -27,20 +27,30 @@ export type Level = {
 }
 
 const ARENA = 12
-const WALL_HEIGHT = 5
+const WALL_HEIGHT = 4
 const CRATE = { x: -2, z: -2, half: 1, top: 1 }
 
+/** Triangle density: grid divisions per world unit, applied to every textured
+ *  surface (floor, walls, crate). Higher = smaller triangles = each spans less
+ *  depth = less affine texture swim, at the cost of more geometry; lower =
+ *  chunkier, wilder PS1 warp (below ~0.5 the floor tips into the black-wedge
+ *  degeneration). Because it scales with surface size, one value keeps the big
+ *  floor and the little crate equally warp-free. Edit and Vite reloads. Pairs
+ *  with the `ps1` preset's `perspectiveCorrect`, which fights the same error
+ *  from the render side. */
+const DIVISIONS_PER_UNIT = 1.3
+
 export function buildLevel(): Level {
   const floor = mesh()
-  quadGrid(floor, [-ARENA, 0, -ARENA], [ARENA, 0, -ARENA], [ARENA, 0, ARENA], [-ARENA, 0, ARENA], 12, 12, 16)
+  quadGrid(floor, [-ARENA, 0, -ARENA], [ARENA, 0, -ARENA], [ARENA, 0, ARENA], [-ARENA, 0, ARENA], 12, 12)
 
   const walls = mesh()
   const h = WALL_HEIGHT
   // Inward-facing perimeter, no ceiling so the sky shows above.
-  quadGrid(walls, [-ARENA, 0, -ARENA], [ARENA, 0, -ARENA], [ARENA, h, -ARENA], [-ARENA, h, -ARENA], 12, 2.5, 12)
+  quadGrid(walls, [-ARENA, 0, -ARENA], [ARENA, 0, -ARENA], [ARENA, h, -ARENA], [-ARENA, h, -ARENA], 12, 2.5)
-  quadGrid(walls, [ARENA, 0, ARENA], [-ARENA, 0, ARENA], [-ARENA, h, ARENA], [ARENA, h, ARENA], 12, 2.5, 12)
+  quadGrid(walls, [ARENA, 0, ARENA], [-ARENA, 0, ARENA], [-ARENA, h, ARENA], [ARENA, h, ARENA], 12, 2.5)
-  quadGrid(walls, [ARENA, 0, -ARENA], [ARENA, 0, ARENA], [ARENA, h, ARENA], [ARENA, h, -ARENA], 12, 2.5, 12)
+  quadGrid(walls, [ARENA, 0, -ARENA], [ARENA, 0, ARENA], [ARENA, h, ARENA], [ARENA, h, -ARENA], 12, 2.5)
-  quadGrid(walls, [-ARENA, 0, ARENA], [-ARENA, 0, -ARENA], [-ARENA, h, -ARENA], [-ARENA, h, ARENA], 12, 2.5, 12)
+  quadGrid(walls, [-ARENA, 0, ARENA], [-ARENA, 0, -ARENA], [-ARENA, h, -ARENA], [-ARENA, h, ARENA], 12, 2.5)
 
   const crate = mesh()
   box(crate, CRATE.x, CRATE.z, CRATE.half, CRATE.top)
@@ -66,6 +76,13 @@ export function buildLevel(): Level {
     sun: Color.rgb(255, 246, 214),
     sunDir: { x: 0.3, y: 0.5, z: -0.8 },
     sunSize: 0.04,
+    clouds: {
+      color: Color.rgb(248, 250, 255),
+      coverage: 0.5,
+      scale: 0.9,
+      speed: 0.5,
+      edge: 0.02,
+    },
   }
 
   return { floor, walls, crate, colliders, npcPosition: { x: 2, y: 0, z: -1 }, sky }
@@ -79,15 +96,18 @@ function wall(minX: number, maxX: number, minZ: number, maxZ: number): Aabb {
   return { minX, maxX, minZ, maxZ, top: WALL_HEIGHT, standable: false }
 }
 
-/** A quad tessellated into an n*n grid so affine texture warp stays per-tile.
+/** Tessellate a quad into a grid sized by DIVISIONS_PER_UNIT, so triangle size
- *  Corners run a (uv 0,0) -> b (us,0) -> c (us,vs) -> d (0,vs). */
+ *  (and thus affine warp) is consistent whatever the surface's scale. Corners
-function quadGrid(m: Mesh, a: Corner, b: Corner, c: Corner, d: Corner, us: number, vs: number, n: number): void {
+ *  run a (uv 0,0) -> b (us,0) -> c (us,vs) -> d (0,vs). */
+function quadGrid(m: Mesh, a: Corner, b: Corner, c: Corner, d: Corner, us: number, vs: number): void {
+  const nu = divisions(a, b)
+  const nv = divisions(a, d)
   const base = m.vertices.length
-  const row = n + 1
+  const row = nu + 1
-  for (let i = 0; i <= n; i++) {
+  for (let i = 0; i <= nv; i++) {
-    const t = i / n
+    const t = i / nv
-    for (let j = 0; j <= n; j++) {
+    for (let j = 0; j <= nu; j++) {
-      const s = j / n
+      const s = j / nu
       const wa = (1 - s) * (1 - t)
       const wb = s * (1 - t)
       const wc = s * t
@@ -102,39 +122,31 @@ function quadGrid(m: Mesh, a: Corner, b: Corner, c: Corner, d: Corner, us: numbe
       })
     }
   }
-  for (let i = 0; i < n; i++) {
+  for (let i = 0; i < nv; i++) {
-    for (let j = 0; j < n; j++) {
+    for (let j = 0; j < nu; j++) {
       const p = base + i * row + j
       m.indices.push(p, p + 1, p + row + 1, p, p + row + 1, p + row)
     }
   }
 }
 
+/** Grid divisions along edge a->b, from its world length and the density. */
+function divisions(a: Corner, b: Corner): number {
+  const length = Math.hypot(b[0] - a[0], b[1] - a[1], b[2] - a[2])
+  return Math.max(1, Math.round(length * DIVISIONS_PER_UNIT))
+}
+
 /** A box centered at (cx, cz) on the floor: top face plus four sides, one uv
- *  tile per face. No bottom (never seen). */
+ *  tile per face. No bottom (never seen). Tessellated like every other surface,
+ *  so it no longer warps up close. */
 function box(m: Mesh, cx: number, cz: number, half: number, top: number): void {
   const x0 = cx - half
   const x1 = cx + half
   const z0 = cz - half
   const z1 = cz + half
-  quad(m, [x0, top, z0], [x1, top, z0], [x1, top, z1], [x0, top, z1])
+  quadGrid(m, [x0, top, z0], [x1, top, z0], [x1, top, z1], [x0, top, z1], 1, 1)
-  quad(m, [x0, 0, z0], [x1, 0, z0], [x1, top, z0], [x0, top, z0])
+  quadGrid(m, [x0, 0, z0], [x1, 0, z0], [x1, top, z0], [x0, top, z0], 1, 1)
-  quad(m, [x1, 0, z1], [x0, 0, z1], [x0, top, z1], [x1, top, z1])
+  quadGrid(m, [x1, 0, z1], [x0, 0, z1], [x0, top, z1], [x1, top, z1], 1, 1)
-  quad(m, [x1, 0, z0], [x1, 0, z1], [x1, top, z1], [x1, top, z0])
+  quadGrid(m, [x1, 0, z0], [x1, 0, z1], [x1, top, z1], [x1, top, z0], 1, 1)
-  quad(m, [x0, 0, z1], [x0, 0, z0], [x0, top, z0], [x0, top, z1])
+  quadGrid(m, [x0, 0, z1], [x0, 0, z0], [x0, top, z0], [x0, top, z1], 1, 1)
-}
-
-function quad(m: Mesh, a: Corner, b: Corner, c: Corner, d: Corner): void {
-  const base = m.vertices.length
-  const corners: [Corner, [number, number]][] = [
-    [a, [0, 0]],
-    [b, [1, 0]],
-    [c, [1, 1]],
-    [d, [0, 1]],
-  ]
-  for (const [pos, uv] of corners) {
-    const vertex: Vertex = { pos: { x: pos[0], y: pos[1], z: pos[2] }, uv: { x: uv[0], y: uv[1] } }
-    m.vertices.push(vertex)
-  }
-  m.indices.push(base, base + 1, base + 2, base, base + 2, base + 3)
 }

app/main.ts

@@ -15,7 +15,7 @@ const ctx = screen.getContext("2d")!
 const back = document.createElement("canvas")
 const backCtx = back.getContext("2d")!
 
-let config: RenderConfig = RenderConfig.psxish
+let config: RenderConfig = RenderConfig.standard
 let fb = Framebuffer.create(1, 1)
 let image = new ImageData(1, 1)
 
@@ -54,7 +54,7 @@ async function main(): Promise<void> {
   globalThis.addEventListener("keydown", (e) => {
     keys.add(e.code)
     if (e.code === "Digit1") {
-      useConfig(RenderConfig.psxish)
+      useConfig(RenderConfig.standard)
     }
     if (e.code === "Digit2") {
       useConfig(RenderConfig.soft)
@@ -95,7 +95,7 @@ async function main(): Promise<void> {
     }
     const viewProj = Camera.viewProjection(camera, fb.width / fb.height)
 
-    Sky.render(fb, camera, level.sky)
+    Sky.render(fb, camera, level.sky, now / 1000)
     Rasterizer.draw(fb, level.floor, textures.floor, viewProj, config)
     Rasterizer.draw(fb, level.walls, textures.wall, viewProj, config)
     Rasterizer.draw(fb, level.crate, textures.crate, viewProj, config)

engine/render/RenderConfig.ts

@@ -62,7 +62,7 @@ export type RenderConfig = {
  *  sweep `perspectiveCorrect` 0 -> 0.5 -> 1 so you can watch the texture swim
  *  straighten out as you press through them. */
 export namespace RenderConfig {
-  export const psxish: RenderConfig = {
+  export const standard: RenderConfig = {
     internalWidth: 384,
     internalHeight: 216,
     upscaleFilter: "nearest",

engine/render/Sky.ts

@@ -3,7 +3,21 @@ import type { Framebuffer } from "./Framebuffer"
 import { Camera } from "../scene/Camera"
 import { Vec3 } from "../math/Vec3"
 
-/** Procedural sky: a vertical gradient plus a sun disc. No texture needed. */
+/** One procedural cloud layer. For now a single cumulus type; add more kinds
+ *  later by giving this a `kind` field and branching in the cloud shader. */
+export type CloudLayer = {
+  color: Color
+  /** Roughly the fraction of sky covered, 0..1. */
+  coverage: number
+  /** Puff size: larger = smaller, busier clouds. */
+  scale: number
+  /** Scroll speed (wind), in noise units per second. */
+  speed: number
+  /** Edge softness: small = crisp cumulus rims, large = hazy. */
+  edge: number
+}
+
+/** Procedural sky: a vertical gradient, a sun disc, and optional moving clouds. */
 export type SkyConfig = {
   zenith: Color
   horizon: Color
@@ -12,6 +26,7 @@ export type SkyConfig = {
   sunDir: Vec3
   /** Angular radius of the sun's core, in radians. */
   sunSize: number
+  clouds: CloudLayer | null
 }
 
 const UP: Vec3 = { x: 0, y: 1, z: 0 }
@@ -20,13 +35,13 @@ export namespace Sky {
   /**
    * Fill the whole framebuffer with the sky and reset depth to 0. Run first each
    * frame in place of Framebuffer.clear; opaque geometry then overwrites the sky
-   * wherever it is nearer.
+   * wherever it is nearer. `time` (seconds) drives cloud motion.
    *
    * Per pixel it reconstructs the view ray from the camera basis, shades a
-   * horizon->zenith gradient by the ray's elevation (so it pans with pitch and
+   * horizon->zenith gradient by the ray's elevation, brightens toward `sun` near
-   * yaw), and brightens toward `sun` where the ray points near `sunDir`.
+   * `sunDir`, then lays crisp-edged cumulus over the top.
    */
-  export function render(fb: Framebuffer, camera: Camera, sky: SkyConfig): void {
+  export function render(fb: Framebuffer, camera: Camera, sky: SkyConfig, time: number): void {
     const { width, height, color, depth } = fb
     const forward = Camera.forward(camera)
     const right = Vec3.normalize(Vec3.cross(forward, UP))
@@ -35,6 +50,7 @@ export namespace Sky {
     const tanX = tanY * (width / height)
     const sun = Vec3.normalize(sky.sunDir)
     const cosSun = Math.cos(sky.sunSize)
+    const clouds = sky.clouds
     for (let y = 0; y < height; y++) {
       const ndcY = 1 - ((y + 0.5) / height) * 2
       for (let x = 0; x < width; x++) {
@@ -55,10 +71,71 @@ export namespace Sky {
           const glow = Math.min(1, ((facing - cosSun) / (1 - cosSun)) * 1.5)
           c = Color.lerp(c, sky.sun, glow)
         }
+        if (clouds !== null && dy > 0.02) {
+          const cover = cumulus(dx, dy, dz, clouds, time)
+          if (cover > 0) {
+            c = Color.lerp(c, clouds.color, cover)
+          }
+        }
         const i = y * width + x
         color[i] = c
         depth[i] = 0
       }
     }
   }
+
+  /**
+   * Coverage in 0..1 of a cumulus layer along a view ray. The ray is projected
+   * onto a flat cloud plane "at infinity" (xz / y), scrolled by wind, sampled
+   * with fractal noise, then hard-thresholded so the clouds have distinct puffy
+   * edges rather than a foggy falloff. Fades out near the horizon, where the
+   * projection blows up into noise.
+   */
+  function cumulus(dx: number, dy: number, dz: number, layer: CloudLayer, time: number): number {
+    const u = (dx / dy) * layer.scale + time * layer.speed
+    const v = (dz / dy) * layer.scale
+    const density = fbm(u, v)
+    const threshold = 0.72 - layer.coverage * 0.4
+    const cover = smoothstep(threshold - layer.edge, threshold + layer.edge, density)
+    return cover * smoothstep(0.02, 0.22, dy)
+  }
+
+  /** Fractal (value-noise) sum, ~0..1, giving lumpy cumulus shapes. */
+  function fbm(x: number, y: number): number {
+    let sum = 0
+    let amplitude = 0.5
+    let frequency = 1
+    for (let octave = 0; octave < 4; octave++) {
+      sum += amplitude * valueNoise(x * frequency, y * frequency)
+      frequency *= 2
+      amplitude *= 0.5
+    }
+    return sum
+  }
+
+  function valueNoise(x: number, y: number): number {
+    const xi = Math.floor(x)
+    const yi = Math.floor(y)
+    const xf = x - xi
+    const yf = y - yi
+    const u = xf * xf * (3 - 2 * xf)
+    const v = yf * yf * (3 - 2 * yf)
+    const a = hash(xi, yi)
+    const b = hash(xi + 1, yi)
+    const c = hash(xi, yi + 1)
+    const d = hash(xi + 1, yi + 1)
+    return a + (b - a) * u + (c - a) * v + (a - b - c + d) * u * v
+  }
+
+  /** Deterministic 0..1 hash of an integer lattice point. */
+  function hash(x: number, y: number): number {
+    let h = (Math.imul(x, 374761393) + Math.imul(y, 668265263)) | 0
+    h = Math.imul(h ^ (h >>> 13), 1274126177)
+    return ((h ^ (h >>> 16)) >>> 0) / 4294967295
+  }
+
+  function smoothstep(a: number, b: number, x: number): number {
+    const t = Math.max(0, Math.min(1, (x - a) / (b - a || 1e-4)))
+    return t * t * (3 - 2 * t)
+  }
 }