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Knightmark

Sprite benchmark with animated knights, collisions, and spatial hashing.

Three.js React

main.ts public/sprites/knight.json

import { WebGPURenderer } from 'three/webgpu'
import { Scene, OrthographicCamera, NearestFilter } from 'three'
import { gemClearColor } from './GemBackground'
import { GEM } from './gem'
import {
  AnimatedSprite2D,
  Sprite2DMaterial,
  SpriteGroup,
  SpriteSheetLoader,
  TextureLoader,
  TileMap2D,
  Layers,
  type AnimationSetDefinition,
  type SpriteSheet,
  type TileMapData,
  type TilesetData,
  type TileLayerData,
  createDevtoolsProvider,
} from 'three-flatland'
import { createPane } from '@three-flatland/devtools'

// ============================================
// CONSTANTS
// ============================================

const SPEED_THRESHOLD = 80
const TRIP_LERP_RATE = 5
const IDLE_AFTER_TRIP_MS = 400

const VIEW_SIZE = 640

// Tilemap
const TILE_PX = 16
const TILE_SCALE = 2

// ============================================
// TWEAKPANE
// ============================================

const { pane, update: updateDevtools } = createPane({ driver: 'manual' })
const devtools = createDevtoolsProvider({ name: 'knightmark' })

// Stats monitors — explicitly refreshed each frame via knightStatsBindings
// below. The default readonly-binding MonitorBinding ticker (200ms) can
// starve when the main thread is busy (heavy allocs, GC pauses), making
// the display look frozen while underlying values are updating. Holding
// the binding refs lets the animate loop force-refresh them per frame.
const knightStats = { knights: 0, batches: 0 }
const statsFolder = pane.addFolder({ title: 'Knights', expanded: false })
const knightStatsBindings = [
  statsFolder.addBinding(knightStats, 'knights', {
    readonly: true,
    format: (v: number) => v.toFixed(0),
  }),
  statsFolder.addBinding(knightStats, 'batches', {
    readonly: true,
    format: (v: number) => v.toFixed(0),
  }),
]

// Simulation params — tweakable at runtime (at bottom, collapsed)
const sim = { speedMin: 30, speedMax: 200, hitRadius: 8, knightScale: 64 }
const simFolder = pane.addFolder({ title: 'Simulation', expanded: false })
simFolder.addBinding(sim, 'speedMin', { min: 10, max: 100, step: 5, label: 'speed min' })
simFolder.addBinding(sim, 'speedMax', { min: 100, max: 300, step: 10, label: 'speed max' })
simFolder.addBinding(sim, 'hitRadius', { min: 2, max: 20, step: 1, label: 'hit radius' })
simFolder.addBinding(sim, 'knightScale', { min: 32, max: 128, step: 8, label: 'scale' })

// ============================================
// TYPES
// ============================================

type KnightState = 'WALK' | 'ROLL' | 'TRIP' | 'TRIP_IDLE'

interface Knight {
  sprite: AnimatedSprite2D
  state: KnightState
  baseVx: number
  baseVy: number
  speed: number
  vx: number
  vy: number
  idleTimer: number
}

// ============================================
// KNIGHT ANIMATIONS
// ============================================

const knightAnimations: AnimationSetDefinition = {
  fps: 10,
  animations: {
    idle: {
      frames: ['idle_0', 'idle_1', 'idle_2', 'idle_3'],
      fps: 8,
      loop: true,
    },
    run: {
      frames: [
        'run_0',
        'run_1',
        'run_2',
        'run_3',
        'run_4',
        'run_5',
        'run_6',
        'run_7',
        'run_8',
        'run_9',
        'run_10',
        'run_11',
        'run_12',
        'run_13',
        'run_14',
        'run_15',
      ],
      fps: 16,
      loop: true,
    },
    roll: {
      frames: ['roll_0', 'roll_1', 'roll_2', 'roll_3', 'roll_4', 'roll_5', 'roll_6', 'roll_7'],
      fps: 15,
      loop: false,
    },
    death: {
      frames: ['death_0', 'death_1', 'death_2', 'death_3'],
      fps: 8,
      loop: false,
    },
  },
}

// ============================================
// SPATIAL HASH
// ============================================

class SpatialHash {
  private cellSize: number
  private cells = new Map<number, Knight[]>()
  private _bucketPool: Knight[][] = []
  private _activeBuckets: Knight[][] = []

  constructor(cellSize: number) {
    this.cellSize = cellSize
  }

  private key(cx: number, cy: number): number {
    const a = cx + 0x8000
    const b = cy + 0x8000
    return (a << 16) | (b & 0xffff)
  }

  clear(): void {
    for (let i = 0; i < this._activeBuckets.length; i++) {
      const bucket = this._activeBuckets[i]!
      bucket.length = 0
      this._bucketPool.push(bucket)
    }
    this._activeBuckets.length = 0
    this.cells.clear()
  }

  insert(knight: Knight): void {
    const cx = Math.floor(knight.sprite.position.x / this.cellSize)
    const cy = Math.floor(knight.sprite.position.y / this.cellSize)
    const k = this.key(cx, cy)
    let bucket = this.cells.get(k)
    if (!bucket) {
      bucket = this._bucketPool.pop() || []
      this._activeBuckets.push(bucket)
      this.cells.set(k, bucket)
    }
    bucket.push(knight)
  }

  forEachNeighbor(knight: Knight, visitor: (other: Knight) => boolean): void {
    const cx = Math.floor(knight.sprite.position.x / this.cellSize)
    const cy = Math.floor(knight.sprite.position.y / this.cellSize)
    for (let dx = -1; dx <= 1; dx++) {
      for (let dy = -1; dy <= 1; dy++) {
        const bucket = this.cells.get(this.key(cx + dx, cy + dy))
        if (bucket) {
          for (let i = 0; i < bucket.length; i++) {
            if (bucket[i] !== knight) {
              if (visitor(bucket[i]!)) return
            }
          }
        }
      }
    }
  }
}

// ============================================
// MAIN
// ============================================

/* HMR-tracked teardown state. Without this, every dev save accumulates
 * a fresh renderer + animate() loop while the previous one keeps
 * RAFing forever. Dev-only — `import.meta.hot` is undefined in prod. */
let rafId = 0
let activeRenderer: WebGPURenderer | null = null

async function main() {
  // WebGPU renderer
  const renderer = new WebGPURenderer({ antialias: false })
  activeRenderer = renderer
  renderer.setSize(window.innerWidth, window.innerHeight)
  renderer.setPixelRatio(1) // Pixel-perfect for pixel art
  renderer.domElement.style.imageRendering = 'pixelated'
  document.body.appendChild(renderer.domElement)
  await renderer.init()

  // Scene
  // L1-only gem clear color — knightmark's sprites fill the viewport, so
  // an L2 fullscreen-quad backdrop would just be hidden. Clear color
  // remains as a safety backstop and tints any margins.
  const scene = new Scene()
  scene.background = gemClearColor(GEM)

  // Orthographic camera
  const aspect = window.innerWidth / window.innerHeight
  const halfW = (VIEW_SIZE * aspect) / 2
  const halfH = VIEW_SIZE / 2
  const camera = new OrthographicCamera(-halfW, halfW, halfH, -halfH, 0.1, 1000)
  camera.position.z = 100

  // SpriteGroup for batching
  const spriteGroup = new SpriteGroup()
  scene.add(spriteGroup)

  // Load assets
  const asset = (path: string) => './' + path
  const [knightSheet, tilesetTexture] = await Promise.all([
    SpriteSheetLoader.load(asset('sprites/knight.json')),
    TextureLoader.load(asset('sprites/Dungeon_Tileset.png')),
  ])

  // Ensure pixel-art filtering for knight sprites
  knightSheet.texture.minFilter = NearestFilter
  knightSheet.texture.magFilter = NearestFilter

  // --- Floor tilemap ---
  // Dungeon_Tileset.png is a 10×10 grid of 16px tiles
  // GID = firstGid + row * columns + col (firstGid=1, columns=10)
  const TS_COLS = 10
  const TS_ROWS = 10

  // Cover the camera view generously (support ultrawide)
  const mapCols = Math.ceil((VIEW_SIZE * 3) / TILE_PX) + 4
  const mapRows = Math.ceil(VIEW_SIZE / TILE_PX) + 4

  // Floor tile pattern — 4×3 clean stone floor from rows 0-2, cols 6-9.
  // The upper-left room tiles have wall shading baked in; these upper-right
  // tiles are the standalone floor meant to be tiled freely.
  const FLOOR_PATTERN = [
    7,
    8,
    9,
    10, // row 0, cols 6-9
    17,
    18,
    19,
    20, // row 1, cols 6-9
    27,
    28,
    29,
    30, // row 2, cols 6-9
  ]

  const floorData = new Uint32Array(mapCols * mapRows)
  for (let y = 0; y < mapRows; y++) {
    for (let x = 0; x < mapCols; x++) {
      floorData[y * mapCols + x] = FLOOR_PATTERN[(y % 3) * 4 + (x % 4)]!
    }
  }

  const tilesetData: TilesetData = {
    name: 'dungeon',
    firstGid: 1,
    tileWidth: TILE_PX,
    tileHeight: TILE_PX,
    imageWidth: TS_COLS * TILE_PX,
    imageHeight: TS_ROWS * TILE_PX,
    columns: TS_COLS,
    tileCount: TS_COLS * TS_ROWS,
    tiles: new Map(),
    texture: tilesetTexture,
  }

  const floorLayer: TileLayerData = {
    name: 'Floor',
    id: 0,
    width: mapCols,
    height: mapRows,
    data: floorData,
  }

  const mapData: TileMapData = {
    width: mapCols,
    height: mapRows,
    tileWidth: TILE_PX,
    tileHeight: TILE_PX,
    orientation: 'orthogonal',
    renderOrder: 'right-down',
    infinite: false,
    tilesets: [tilesetData],
    tileLayers: [floorLayer],
    objectLayers: [],
  }

  const tilemap = new TileMap2D({ data: mapData, enableCollision: false })
  tilemap.scale.set(TILE_SCALE, TILE_SCALE, 1)
  const mapWorldW = mapCols * TILE_PX * TILE_SCALE
  const mapWorldH = mapRows * TILE_PX * TILE_SCALE
  tilemap.position.set(-mapWorldW / 2, -mapWorldH / 2, -1)
  scene.add(tilemap)

  // --- Bounce bounds = camera view edges ---
  let boundsLeft = -halfW
  let boundsRight = halfW
  let boundsTop = halfH
  let boundsBottom = -halfH

  // --- Knights ---
  const knights: Knight[] = []
  const spatialHash = new SpatialHash(sim.hitRadius * 4)

  // Shared material with alphaTest > 0 → opaque bucket → GPU depth-test
  // fast path (no CPU zIndex sort needed for batches using this material).
  const material = Sprite2DMaterial.getShared({ map: knightSheet.texture, alphaTest: 0.5 })

  function spawnKnight(sheet: SpriteSheet): Knight {
    const margin = sim.knightScale / 2
    const sprite = new AnimatedSprite2D({
      spriteSheet: sheet,
      animationSet: knightAnimations,
      animation: 'idle',
      layer: Layers.ENTITIES,
      anchor: [0.5, 0.5],
      material,
    })
    sprite.scale.set(sim.knightScale, sim.knightScale, 1)
    const x = boundsLeft + margin + Math.random() * (boundsRight - boundsLeft - margin * 2)
    const y = boundsBottom + margin + Math.random() * (boundsTop - boundsBottom - margin * 2)
    sprite.position.set(x, y, 0)
    const speed = sim.speedMin + Math.random() * (sim.speedMax - sim.speedMin)
    const angle = Math.random() * Math.PI * 2
    const baseVx = Math.cos(angle) * speed
    const baseVy = Math.sin(angle) * speed
    const animName = speed < SPEED_THRESHOLD ? 'idle' : 'run'
    sprite.play(animName)
    sprite.flipX = baseVx < 0
    spriteGroup.add(sprite)
    return {
      sprite,
      state: 'WALK',
      baseVx,
      baseVy,
      speed,
      vx: baseVx,
      vy: baseVy,
      idleTimer: 0,
    }
  }

  function spawnBatch(count: number) {
    for (let i = 0; i < count; i++) knights.push(spawnKnight(knightSheet))
  }

  function triggerTrip(knight: Knight) {
    knight.state = 'TRIP'
    knight.sprite.play('death', {
      onComplete: () => {
        knight.state = 'TRIP_IDLE'
        knight.idleTimer = IDLE_AFTER_TRIP_MS
        knight.sprite.play('idle')
      },
    })
  }

  function triggerRoll(knight: Knight) {
    knight.state = 'ROLL'
    knight.sprite.play('roll', {
      onComplete: () => {
        knight.state = 'WALK'
        const animName = knight.speed < SPEED_THRESHOLD ? 'idle' : 'run'
        knight.sprite.play(animName)
      },
    })
  }

  const urlSpawn = parseInt(new URLSearchParams(window.location.search).get('spawn') ?? '', 10)
  spawnBatch(Number.isFinite(urlSpawn) && urlSpawn > 0 ? urlSpawn : 10)

  // --- UI ---
  const addBtn = document.getElementById('btn-add')!
  addBtn.addEventListener('click', () => spawnBatch(100))
  window.addEventListener('keydown', (e) => {
    if (e.code === 'Space') {
      e.preventDefault()
      spawnBatch(100)
    }
  })

  // --- Resize ---
  function handleResize() {
    const newAspect = window.innerWidth / window.innerHeight
    const newHalfW = (VIEW_SIZE * newAspect) / 2
    const newHalfH = VIEW_SIZE / 2
    camera.left = -newHalfW
    camera.right = newHalfW
    camera.top = newHalfH
    camera.bottom = -newHalfH
    camera.updateProjectionMatrix()
    renderer.setSize(window.innerWidth, window.innerHeight)
    boundsLeft = -newHalfW
    boundsRight = newHalfW
    boundsTop = newHalfH
    boundsBottom = -newHalfH
  }
  window.addEventListener('resize', handleResize)

  // --- Animation loop ---
  let lastTime = performance.now()
  function animate() {
    rafId = requestAnimationFrame(animate)
    const now = performance.now()
    const deltaMs = now - lastTime
    lastTime = now
    const dt = deltaMs / 1000

    // Derive cell size from current hitRadius
    const cellSize = sim.hitRadius * 4

    // Update knight movement and animation
    const margin = sim.knightScale / 2
    for (const k of knights) {
      switch (k.state) {
        case 'WALK':
        case 'ROLL':
          k.vx = k.baseVx
          k.vy = k.baseVy
          break
        case 'TRIP':
          k.vx += (0 - k.vx) * Math.min(1, TRIP_LERP_RATE * dt)
          k.vy += (0 - k.vy) * Math.min(1, TRIP_LERP_RATE * dt)
          break
        case 'TRIP_IDLE':
          k.vx = 0
          k.vy = 0
          k.idleTimer -= deltaMs
          if (k.idleTimer <= 0) {
            k.state = 'WALK'
            k.vx = k.baseVx
            k.vy = k.baseVy
            const animName = k.speed < SPEED_THRESHOLD ? 'idle' : 'run'
            k.sprite.play(animName)
          }
          break
      }
      k.sprite.position.x += k.vx * dt
      k.sprite.position.y += k.vy * dt

      // Bounce off screen edges
      if (k.sprite.position.x < boundsLeft + margin) {
        k.sprite.position.x = boundsLeft + margin
        k.baseVx = Math.abs(k.baseVx)
        k.vx = Math.abs(k.vx)
      } else if (k.sprite.position.x > boundsRight - margin) {
        k.sprite.position.x = boundsRight - margin
        k.baseVx = -Math.abs(k.baseVx)
        k.vx = -Math.abs(k.vx)
      }
      if (k.sprite.position.y < boundsBottom + margin) {
        k.sprite.position.y = boundsBottom + margin
        k.baseVy = Math.abs(k.baseVy)
        k.vy = Math.abs(k.vy)
      } else if (k.sprite.position.y > boundsTop - margin) {
        k.sprite.position.y = boundsTop - margin
        k.baseVy = -Math.abs(k.baseVy)
        k.vy = -Math.abs(k.vy)
      }
      k.sprite.flipX = k.baseVx < 0
      k.sprite.zIndex = -Math.floor(k.sprite.position.y)
      k.sprite.update(deltaMs)
    }

    // Knight-knight collisions via spatial hash
    spatialHash.clear()
    // Update spatial hash cell size from current hitRadius
    ;(spatialHash as unknown as { cellSize: number }).cellSize = cellSize
    for (const k of knights) spatialHash.insert(k)
    const collisionDist = sim.hitRadius * 2
    const collisionDistSq = collisionDist * collisionDist
    for (const k of knights) {
      if (k.state !== 'WALK') continue
      spatialHash.forEachNeighbor(k, (other) => {
        if (other.state !== 'WALK') return false
        const dx = other.sprite.position.x - k.sprite.position.x
        const dy = other.sprite.position.y - k.sprite.position.y
        const distSq = dx * dx + dy * dy
        if (distSq < collisionDistSq) {
          const tripChanceA = k.speed / (k.speed + other.speed)
          if (Math.random() < tripChanceA) {
            triggerTrip(k)
            triggerRoll(other)
          } else {
            triggerTrip(other)
            triggerRoll(k)
          }
          return true
        }
        return false
      })
    }

    // Render — systems run automatically in updateMatrixWorld
    devtools.beginFrame(performance.now(), renderer)
    renderer.render(scene, camera)
    devtools.endFrame(renderer)
    updateDevtools()

    // Knight batch monitors
    const s = spriteGroup.stats
    knightStats.knights = knights.length
    knightStats.batches = s.batchCount
  }
  animate()
}
main()

if (import.meta.hot) {
  import.meta.hot.dispose(() => {
    if (rafId) {
      cancelAnimationFrame(rafId)
      rafId = 0
    }
    if (activeRenderer) {
      activeRenderer.dispose?.()
      activeRenderer.domElement.remove()
      activeRenderer = null
    }
  })
}

App.tsx public/sprites/knight.json

import { Suspense, useRef, useMemo, useCallback, useEffect } from 'react'
import type { OrthographicCamera } from 'three'
import { Canvas, extend, useFrame, useThree, useLoader } from '@react-three/fiber/webgpu'
import {
  AnimatedSprite2D,
  Sprite2DMaterial,
  SpriteGroup,
  SpriteSheetLoader,
  TextureLoader,
  TileMap2D,
  Layers,
  type AnimationSetDefinition,
  type SpriteSheet,
  type TileMapData,
  type TilesetData,
  type TileLayerData,
} from 'three-flatland/react'
import { DevtoolsProvider, usePane, usePaneFolder, usePaneInput } from '@three-flatland/devtools/react'
// Knightmark doesn't render any gem-background layer — its sprites
// fill the viewport. The body bg (#16191e) shows through during
// initial sprite load. GEM/GemBackground imports intentionally
// omitted; the per-example `gem.ts` is still synced for consistency.

extend({ SpriteGroup, TileMap2D })

function OrthoCamera({ viewSize }: { viewSize: number }) {
  const set = useThree((s) => s.set)
  const size = useThree((s) => s.size)
  const aspect = size.width / size.height
  return (
    <orthographicCamera
      ref={(cam: OrthographicCamera | null) => {
        if (!cam) return
        cam.left = (-viewSize * aspect) / 2
        cam.right = (viewSize * aspect) / 2
        cam.top = viewSize / 2
        cam.bottom = -viewSize / 2
        cam.updateProjectionMatrix()
        set({ camera: cam })
      }}
      position={[0, 0, 100]}
      near={0.1}
      far={1000}
      manual
    />
  )
}

// ============================================
// CONSTANTS
// ============================================

const SPEED_THRESHOLD = 80
const TRIP_LERP_RATE = 5
const IDLE_AFTER_TRIP_MS = 400

const VIEW_SIZE = 640

// Tilemap
const TILE_PX = 16
const TILE_SCALE = 2

// ============================================
// TYPES
// ============================================

type KnightState = 'WALK' | 'ROLL' | 'TRIP' | 'TRIP_IDLE'

interface Knight {
  sprite: AnimatedSprite2D
  state: KnightState
  baseVx: number
  baseVy: number
  speed: number
  vx: number
  vy: number
  idleTimer: number
}

// ============================================
// KNIGHT ANIMATIONS
// ============================================

const knightAnimations: AnimationSetDefinition = {
  fps: 10,
  animations: {
    idle: {
      frames: ['idle_0', 'idle_1', 'idle_2', 'idle_3'],
      fps: 8,
      loop: true,
    },
    run: {
      frames: [
        'run_0',
        'run_1',
        'run_2',
        'run_3',
        'run_4',
        'run_5',
        'run_6',
        'run_7',
        'run_8',
        'run_9',
        'run_10',
        'run_11',
        'run_12',
        'run_13',
        'run_14',
        'run_15',
      ],
      fps: 16,
      loop: true,
    },
    roll: {
      frames: ['roll_0', 'roll_1', 'roll_2', 'roll_3', 'roll_4', 'roll_5', 'roll_6', 'roll_7'],
      fps: 15,
      loop: false,
    },
    death: {
      frames: ['death_0', 'death_1', 'death_2', 'death_3'],
      fps: 8,
      loop: false,
    },
  },
}

// ============================================
// SPATIAL HASH
// ============================================

class SpatialHash {
  cellSize: number
  private cells = new Map<number, Knight[]>()
  private _bucketPool: Knight[][] = []
  private _activeBuckets: Knight[][] = []

  constructor(cellSize: number) {
    this.cellSize = cellSize
  }

  private key(cx: number, cy: number): number {
    const a = cx + 0x8000
    const b = cy + 0x8000
    return (a << 16) | (b & 0xffff)
  }

  clear(): void {
    for (let i = 0; i < this._activeBuckets.length; i++) {
      const bucket = this._activeBuckets[i]!
      bucket.length = 0
      this._bucketPool.push(bucket)
    }
    this._activeBuckets.length = 0
    this.cells.clear()
  }

  insert(knight: Knight): void {
    const cx = Math.floor(knight.sprite.position.x / this.cellSize)
    const cy = Math.floor(knight.sprite.position.y / this.cellSize)
    const k = this.key(cx, cy)
    let bucket = this.cells.get(k)
    if (!bucket) {
      bucket = this._bucketPool.pop() || []
      this._activeBuckets.push(bucket)
      this.cells.set(k, bucket)
    }
    bucket.push(knight)
  }

  forEachNeighbor(knight: Knight, visitor: (other: Knight) => boolean): void {
    const cx = Math.floor(knight.sprite.position.x / this.cellSize)
    const cy = Math.floor(knight.sprite.position.y / this.cellSize)
    for (let dx = -1; dx <= 1; dx++) {
      for (let dy = -1; dy <= 1; dy++) {
        const bucket = this.cells.get(this.key(cx + dx, cy + dy))
        if (bucket) {
          for (let i = 0; i < bucket.length; i++) {
            if (bucket[i] !== knight) {
              if (visitor(bucket[i]!)) return
            }
          }
        }
      }
    }
  }
}

// ============================================
// STATE TRANSITIONS
// ============================================

function triggerTrip(knight: Knight) {
  knight.state = 'TRIP'
  knight.sprite.play('death', {
    onComplete: () => {
      knight.state = 'TRIP_IDLE'
      knight.idleTimer = IDLE_AFTER_TRIP_MS
      knight.sprite.play('idle')
    },
  })
}

function triggerRoll(knight: Knight) {
  knight.state = 'ROLL'
  knight.sprite.play('roll', {
    onComplete: () => {
      knight.state = 'WALK'
      const animName = knight.speed < SPEED_THRESHOLD ? 'idle' : 'run'
      knight.sprite.play(animName)
    },
  })
}

// ============================================
// SPAWN HELPER
// ============================================

function spawnKnight(
  sheet: SpriteSheet,
  spriteGroup: SpriteGroup,
  bounds: { left: number; right: number; top: number; bottom: number },
  simParams: { speedMin: number; speedMax: number; knightScale: number }
): Knight {
  const margin = simParams.knightScale / 2
  // Opaque alphaTest material enables the GPU depth-test fast path:
  // the y-sort (zIndex = -y) is resolved by the depth buffer, so the
  // CPU batchSortSystem can skip this batch entirely.
  const material = Sprite2DMaterial.getShared({
    map: sheet.texture,
    alphaTest: 0.5,
  })
  const sprite = new AnimatedSprite2D({
    spriteSheet: sheet,
    animationSet: knightAnimations,
    animation: 'idle',
    layer: Layers.ENTITIES,
    anchor: [0.5, 0.5],
    material,
  })
  sprite.scale.set(simParams.knightScale, simParams.knightScale, 1)
  const x = bounds.left + margin + Math.random() * (bounds.right - bounds.left - margin * 2)
  const y = bounds.bottom + margin + Math.random() * (bounds.top - bounds.bottom - margin * 2)
  sprite.position.set(x, y, 0)
  const speed = simParams.speedMin + Math.random() * (simParams.speedMax - simParams.speedMin)
  const angle = Math.random() * Math.PI * 2
  const baseVx = Math.cos(angle) * speed
  const baseVy = Math.sin(angle) * speed
  const animName = speed < SPEED_THRESHOLD ? 'idle' : 'run'
  sprite.play(animName)
  sprite.flipX = baseVx < 0
  spriteGroup.add(sprite)
  return {
    sprite,
    state: 'WALK',
    baseVx,
    baseVy,
    speed,
    vx: baseVx,
    vy: baseVy,
    idleTimer: 0,
  }
}

// ============================================
// SCENE COMPONENT
// ============================================

interface KnightmarkSceneProps {
  addKnightsRef: React.RefObject<(() => void) | null>
  speedMin: number
  speedMax: number
  hitRadius: number
  knightScale: number
  knightStatsRef: React.RefObject<{ knights: number; batches: number }>
}

function KnightmarkScene({
  addKnightsRef,
  speedMin,
  speedMax,
  hitRadius,
  knightScale,
  knightStatsRef,
}: KnightmarkSceneProps) {
  const { size } = useThree()

  // Load assets (presets automatically apply NearestFilter)
  const knightSheet = useLoader(SpriteSheetLoader, './sprites/knight.json')
  const tilesetTex = useLoader(TextureLoader, './sprites/Dungeon_Tileset.png')

  const spriteGroupRef = useRef<SpriteGroup>(null)
  const knightsRef = useRef<Knight[]>([])
  const spatialHashRef = useRef(new SpatialHash(hitRadius * 4))
  const boundsRef = useRef({ left: 0, right: 0, top: 0, bottom: 0 })

  // Store latest sim params in refs for use in useFrame
  const simRef = useRef({ speedMin, speedMax, hitRadius, knightScale })
  simRef.current = { speedMin, speedMax, hitRadius, knightScale }

  // Track world bounds for spawn/cleanup logic (camera frustum is set by <OrthoCamera>)
  useEffect(() => {
    const aspect = size.width / size.height
    const halfW = (VIEW_SIZE * aspect) / 2
    const halfH = VIEW_SIZE / 2
    boundsRef.current = { left: -halfW, right: halfW, top: halfH, bottom: -halfH }
  }, [size])

  // Build floor tilemap data
  const { mapData, mapWorldW, mapWorldH } = useMemo(() => {
    const TS_COLS = 10
    const TS_ROWS = 10

    // Cover the camera view generously (support ultrawide)
    const mapCols = Math.ceil((VIEW_SIZE * 3) / TILE_PX) + 4
    const mapRows = Math.ceil(VIEW_SIZE / TILE_PX) + 4

    // Floor tile pattern — 4×3 clean stone floor from rows 0-2, cols 6-9.
    const FLOOR_PATTERN = [7, 8, 9, 10, 17, 18, 19, 20, 27, 28, 29, 30]

    const floorData = new Uint32Array(mapCols * mapRows)
    for (let y = 0; y < mapRows; y++) {
      for (let x = 0; x < mapCols; x++) {
        floorData[y * mapCols + x] = FLOOR_PATTERN[(y % 3) * 4 + (x % 4)]!
      }
    }

    const tilesetData: TilesetData = {
      name: 'dungeon',
      firstGid: 1,
      tileWidth: TILE_PX,
      tileHeight: TILE_PX,
      imageWidth: TS_COLS * TILE_PX,
      imageHeight: TS_ROWS * TILE_PX,
      columns: TS_COLS,
      tileCount: TS_COLS * TS_ROWS,
      tiles: new Map(),
      texture: tilesetTex,
    }

    const floorLayer: TileLayerData = {
      name: 'Floor',
      id: 0,
      width: mapCols,
      height: mapRows,
      data: floorData,
    }

    const data: TileMapData = {
      width: mapCols,
      height: mapRows,
      tileWidth: TILE_PX,
      tileHeight: TILE_PX,
      orientation: 'orthogonal',
      renderOrder: 'right-down',
      infinite: false,
      tilesets: [tilesetData],
      tileLayers: [floorLayer],
      objectLayers: [],
    }

    return {
      mapData: data,
      mapWorldW: mapCols * TILE_PX * TILE_SCALE,
      mapWorldH: mapRows * TILE_PX * TILE_SCALE,
    }
  }, [tilesetTex])

  // Spawn batch of knights
  const spawnBatch = useCallback(
    (count: number) => {
      const r2d = spriteGroupRef.current
      if (!r2d) return
      const bounds = boundsRef.current
      const sim = simRef.current
      for (let i = 0; i < count; i++) {
        knightsRef.current.push(spawnKnight(knightSheet, r2d, bounds, sim))
      }
    },
    [knightSheet]
  )

  // Initial spawn + expose add handler
  useEffect(() => {
    spawnBatch(10)
    addKnightsRef.current = () => spawnBatch(100)
    return () => {
      addKnightsRef.current = null
    }
  }, [spawnBatch, addKnightsRef])

  // Game loop
  useFrame((_, delta) => {
    const dt = delta
    const deltaMs = delta * 1000
    const knights = knightsRef.current
    const spatialHash = spatialHashRef.current
    const bounds = boundsRef.current
    const sim = simRef.current
    const margin = sim.knightScale / 2

    // Update spatial hash cell size from current hitRadius
    spatialHash.cellSize = sim.hitRadius * 4

    // Update knight movement and animation
    for (const k of knights) {
      switch (k.state) {
        case 'WALK':
        case 'ROLL':
          k.vx = k.baseVx
          k.vy = k.baseVy
          break
        case 'TRIP':
          k.vx += (0 - k.vx) * Math.min(1, TRIP_LERP_RATE * dt)
          k.vy += (0 - k.vy) * Math.min(1, TRIP_LERP_RATE * dt)
          break
        case 'TRIP_IDLE':
          k.vx = 0
          k.vy = 0
          k.idleTimer -= deltaMs
          if (k.idleTimer <= 0) {
            k.state = 'WALK'
            k.vx = k.baseVx
            k.vy = k.baseVy
            const animName = k.speed < SPEED_THRESHOLD ? 'idle' : 'run'
            k.sprite.play(animName)
          }
          break
      }
      k.sprite.position.x += k.vx * dt
      k.sprite.position.y += k.vy * dt

      // Bounce off screen edges
      if (k.sprite.position.x < bounds.left + margin) {
        k.sprite.position.x = bounds.left + margin
        k.baseVx = Math.abs(k.baseVx)
        k.vx = Math.abs(k.vx)
      } else if (k.sprite.position.x > bounds.right - margin) {
        k.sprite.position.x = bounds.right - margin
        k.baseVx = -Math.abs(k.baseVx)
        k.vx = -Math.abs(k.vx)
      }
      if (k.sprite.position.y < bounds.bottom + margin) {
        k.sprite.position.y = bounds.bottom + margin
        k.baseVy = Math.abs(k.baseVy)
        k.vy = Math.abs(k.vy)
      } else if (k.sprite.position.y > bounds.top - margin) {
        k.sprite.position.y = bounds.top - margin
        k.baseVy = -Math.abs(k.baseVy)
        k.vy = -Math.abs(k.vy)
      }
      k.sprite.flipX = k.baseVx < 0
      k.sprite.zIndex = -Math.floor(k.sprite.position.y)
      k.sprite.update(deltaMs)
    }

    // Knight-knight collisions via spatial hash
    spatialHash.clear()
    for (const k of knights) spatialHash.insert(k)
    const collisionDist = sim.hitRadius * 2
    const collisionDistSq = collisionDist * collisionDist
    for (const k of knights) {
      if (k.state !== 'WALK') continue
      spatialHash.forEachNeighbor(k, (other) => {
        if (other.state !== 'WALK') return false
        const dx = other.sprite.position.x - k.sprite.position.x
        const dy = other.sprite.position.y - k.sprite.position.y
        const distSq = dx * dx + dy * dy
        if (distSq < collisionDistSq) {
          const tripChanceA = k.speed / (k.speed + other.speed)
          if (Math.random() < tripChanceA) {
            triggerTrip(k)
            triggerRoll(other)
          } else {
            triggerTrip(other)
            triggerRoll(k)
          }
          return true
        }
        return false
      })
    }

    // Update knight-batch monitors. Refresh bindings every frame — the
    // default readonly-binding MonitorBinding ticker (200ms) can starve
    // under heavy main-thread load (allocs, GC pauses), making the
    // display freeze even while the underlying values keep updating.
    if (spriteGroupRef.current) {
      const s = spriteGroupRef.current.stats
      knightStatsRef.current.knights = knights.length
      knightStatsRef.current.batches = s.batchCount
    }
  })

  return (
    <>
      <tileMap2D
        data={mapData}
        enableCollision={false}
        scale={[TILE_SCALE, TILE_SCALE, 1]}
        position={[-mapWorldW / 2, -mapWorldH / 2, -1]}
      />
      <spriteGroup ref={spriteGroupRef} />
    </>
  )
}

// ============================================
// APP
// ============================================

export default function App() {
  const addKnightsRef = useRef<(() => void) | null>(null)

  // Tweakpane
  const { pane } = usePane()

  // Knights monitors (first)
  const knightStatsRef = useRef({ knights: 0, batches: 0 })
  const statsFolder = usePaneFolder(pane, 'Knights')

  // Simulation folder (at bottom, collapsed)
  const simFolder = usePaneFolder(pane, 'Simulation')
  const [speedMin] = usePaneInput(simFolder, 'speedMin', 30, {
    min: 10,
    max: 100,
    step: 5,
    label: 'speed min',
  })
  const [speedMax] = usePaneInput(simFolder, 'speedMax', 200, {
    min: 100,
    max: 300,
    step: 10,
    label: 'speed max',
  })
  const [hitRadius] = usePaneInput(simFolder, 'hitRadius', 8, {
    min: 2,
    max: 20,
    step: 1,
    label: 'hit radius',
  })
  const [knightScale] = usePaneInput(simFolder, 'knightScale', 64, {
    min: 32,
    max: 128,
    step: 8,
    label: 'scale',
  })
  // Refresh callback driven from KnightmarkScene's useFrame — see
  // `refreshStatsRef.current()` call in the per-frame block. Per-frame
  // refresh keeps the readout current under heavy load (GC pauses can
  // starve tweakpane's 200ms internal ticker, leaving the display
  // frozen while underlying values keep updating).
  const refreshStatsRef = useRef<() => void>(() => {})
  useEffect(() => {
    if (!statsFolder) return
    const bKnights = statsFolder.addBinding(knightStatsRef.current, 'knights', {
      readonly: true,
      format: (v: number) => v.toFixed(0),
    })
    const bBatches = statsFolder.addBinding(knightStatsRef.current, 'batches', {
      readonly: true,
      format: (v: number) => v.toFixed(0),
    })
    refreshStatsRef.current = () => {
      bKnights.refresh()
      bBatches.refresh()
    }
    return () => {
      refreshStatsRef.current = () => {}
      bKnights.dispose()
      bBatches.dispose()
    }
  }, [statsFolder])

  // Keyboard: Space to add knights
  useEffect(() => {
    const handler = (e: KeyboardEvent) => {
      if (e.code === 'Space') {
        e.preventDefault()
        addKnightsRef.current?.()
      }
    }
    window.addEventListener('keydown', handler)
    return () => window.removeEventListener('keydown', handler)
  }, [])

  return (
    <>
      <Canvas
        dpr={1}
        renderer={{ antialias: false }}
        onCreated={({ gl }) => {
          gl.domElement.style.imageRendering = 'pixelated'
        }}
      >
        <OrthoCamera viewSize={VIEW_SIZE} />
        <DevtoolsProvider name="knightmark" />
        {/* No L1/L2/L3 — knightmark's sprites fill the viewport, so a
           backdrop wouldn't be visible anyway. Body bg (#16191e) shows
           through during initial sprite load, no color jump. */}
        <Suspense fallback={null}>
          <KnightmarkScene
            addKnightsRef={addKnightsRef}
            speedMin={speedMin}
            speedMax={speedMax}
            hitRadius={hitRadius}
            knightScale={knightScale}
            knightStatsRef={knightStatsRef}
          />
        </Suspense>
      </Canvas>

      {/* TODO: migrate game UI to three-flatland events */}
      <div
        style={{
          position: 'fixed',
          bottom: 16,
          left: '50%',
          transform: 'translateX(-50%)',
          display: 'flex',
          gap: 10,
          zIndex: 100,
        }}
      >
        <button
          onClick={() => addKnightsRef.current?.()}
          style={{
            padding: '10px 24px',
            fontSize: 14,
            fontFamily: 'monospace',
            border: '2px solid #4a9eff',
            background: 'rgba(74,158,255,0.1)',
            color: '#4a9eff',
            cursor: 'pointer',
            borderRadius: 4,
            transition: 'background 0.15s',
          }}
        >
          + 100 Knights (Space)
        </button>
      </div>
    </>
  )
}

What It Demonstrates

Knightmark is a sprite stress test inspired by classic benchmarks like Bunnymark. It showcases:

• Batch rendering — thousands of animated sprites in minimal draw calls
• AnimatedSprite2D — frame-based sprite animation with multiple states
• Spatial hashing — efficient collision detection between sprites
• Y-sorting — depth-correct rendering via zIndex

Key Patterns

Animated Sprites with State Machines

Each knight has a state machine (walk, roll, trip, idle) driving its animation:

const sprite = new AnimatedSprite2D({
  spriteSheet: knightSheet,
  animationSet: knightAnimations,
  animation: 'idle',
  layer: Layers.ENTITIES,
});

sprite.play('run');
sprite.play('death', {
  onComplete: () => sprite.play('idle'),
});

Y-Sort Depth Ordering

Knights render in correct depth order by setting zIndex from their Y position:

sprite.zIndex = -Math.floor(sprite.position.y);

Spatial Hash for Collisions

A simple spatial hash grid enables O(n) collision checks instead of O(n^2):

spatialHash.clear();
for (const knight of knights) spatialHash.insert(knight);

spatialHash.forEachNeighbor(knight, (other) => {
  // Check distance and resolve collision
});

Further Reading

• Batch Rendering - Learn more about batching
• Animation - Sprite animation basics