Optimizing Decentraland Scenes

Scene Limits (Per Parcel Count)

All limits scale with parcel count n. Triangles, entities, and bodies scale linearly. Materials, textures, and height scale logarithmically.

Read the Materials row with care. The client instantiates a material per rendered object, so this number tracks how many objects a scene renders rather than how many distinct materials it authors — a scene that correctly reuses one model many times will pass this cap while doing the right thing. Treat it as a memory signal, and judge frame-time risk by shaderVariants instead (see Repeated Models below).

File limits: 15 MB per parcel, 300 MB max total, 200 files per parcel, 50 MB max per individual file.

File limits count only what is actually uploaded on deploy. Make sure .dclignore (at the project root) excludes all working files — Blender/FBX sources, draft models, concept art, spreadsheets, markdown docs — since these are often the bulk of a project's size and are never needed at runtime. See the .dclignore section in the deploy-scene skill.

Important: Except for the MB size limits, all other limits can be exceeded. It's generally not recommended to go over them because of performance impact, but if a user tests their scene and determines that it's good enough, it should be ok to publish.

Entity Count Optimization

Reuse Entities

Use this pattern only for cases where the scene should be spawning and removing instances dynamically.

// BAD: Creating new entity each time
function spawnBullet() {
	const bullet = engine.addEntity() // Creates entity every call
	// ...
}

// GOOD: Object pooling
const bulletPool: Entity[] = []
function getBullet(): Entity {
	const existing = bulletPool.find((e) => !ActiveBullet.has(e))
	if (existing) return existing
	const newBullet = engine.addEntity()
	bulletPool.push(newBullet)
	return newBullet
}

Remove Unused Entities

const removed = engine.removeEntity(entity) // returns boolean
// true: components purged, id released for reuse
// false: entity is renderer-reserved (avatar range) — components untouched

Use Parenting

Instead of independent transform values for each child, use entity hierarchy:

const parent = engine.addEntity()
Transform.create(parent, { position: Vector3.create(8, 0, 8) })

// Children inherit parent transform
const child1 = engine.addEntity()
Transform.create(child1, { position: Vector3.create(0, 1, 0), parent })

const child2 = engine.addEntity()
Transform.create(child2, { position: Vector3.create(1, 1, 0), parent })

Repeated Models (Reuse vs Merge)

For repeated content — lamp posts, chairs, trees, fences — default to one entity per copy, all pointing at the same .glb. The engine dedups by source: one download, one asset-bundle conversion, one copy of the meshes and textures in memory, no matter how many entities use it. The dedup is global for the session, so a neighboring scene using the same file gets it for free.

// GOOD: one file, many entities — engine shares the loaded asset
for (const position of lampPostPositions) {
	const lampPost = engine.addEntity()
	Transform.create(lampPost, { position })
	GltfContainer.create(lampPost, { src: 'assets/scene/lampPost.glb' })
}

// BAD: near-identical files — 20 downloads, 20 copies in memory
// lampPost_01.glb, lampPost_02.glb, ... lampPost_20.glb

What reuse does NOT save: draw calls. 20 lamp posts are 20 renderers either way — whether from 20 entities or from one .glb with 20 lamp posts modeled into it. There is no runtime batching or GPU instancing for scene content: the client streams and builds scenes at runtime, so it cannot group repeated objects the way an engine can with pre-baked content. Draw count is fixed at author time.

Only the third row reduces draw calls, and it costs file size, memory, and per-object culling. Recommend it only when: many small props, always co-visible in one spot, never interactive, AND a measurement showed renderer count is the bottleneck. Otherwise recommend reuse.

Middle ground for scattered props: one .glb per cluster (a street block, a room's furniture) rather than one-per-prop or one-for-the-whole-scene. Cuts renderer count while keeping clusters small enough for culling to help.

Three more consequences worth knowing:

• Reuse does NOT reduce material count either. The client instantiates a material per renderer to write the scene's boundary clipping, so materials in the stats tracks rendered objects, not distinct models — measured: 14 entities on one shared .glb report 28 renderers and 28 materials, while geometries and textures stay at one copy. Those instances share the same textures and shader variants, so this is a small memory cost, not a frame-time one. Never recommend material dedup as a frame-time fix without checking shaderVariants first.
• Spawning many copies at once? Preload with AssetLoad first (see below) so copies come from a resident asset instead of each awaiting the same download. It does not make the copies free: building them is ~90% of a burst's cost even when the asset is already resident, so a large burst can still cost a frame.
• One huge model is worse than many small ones for load smoothness. Asset creation is spread across frames under a frame-time budget, but a single enormous model cannot be split — it lands in one frame and is far more likely to cause a visible hiccup.

See the gltf-reuse-vs-merge benchmark scene for a concrete measurement: it spawns the same lamp post model via reuse (one .glb, many entities), via duplicate files, and via a merged .glb, comparing renderer/material counts, memory, and load behavior. It also demonstrates AssetLoad preloading and collision-mask tuning for burst spawning.

Triangle Count Optimization

Use Lower-Poly Models

• Small props: 100-500 triangles
• Medium objects: 500-1,500 triangles
• Large buildings: 1,500-5,000 triangles
• Hero pieces: Up to 10,000 triangles

Use LOD (Level of Detail)

Show simpler models at distance:

engine.addSystem(() => {
	// Check distance to player and swap models
	const playerPos = Transform.get(engine.PlayerEntity).position
	const objPos = Transform.get(myEntity).position
	const distance = Vector3.distance(playerPos, objPos)

	const gltf = GltfContainer.getMutable(myEntity)
	if (distance > 30) {
		gltf.src = 'models/building_lod2.glb' // Low poly
	} else if (distance > 15) {
		gltf.src = 'models/building_lod1.glb' // Medium poly
	} else {
		gltf.src = 'models/building_lod0.glb' // High poly
	}
})

Use Primitives Instead of Models

For simple shapes, MeshRenderer is lighter than loading a .glb:

MeshRenderer.setBox(entity) // Very cheap
MeshRenderer.setSphere(entity) // Cheap
MeshRenderer.setPlane(entity) // Very cheap

Fix Heavy Models in Blender

When the stats point at specific models — a prop with tens of thousands of triangles, a GLB carrying 2048+ textures, meshes full of faces the player never sees — fix the asset itself by driving Blender rather than compensating in SDK code. The full guide (headless CLI vs Blender MCP, setup, export rules) is in {baseDir}/../add-3d-models/references/blender-authoring.md, with ready-made bpy scripts in {baseDir}/../add-3d-models/references/blender-patterns.md. Typical rescue edits:

• Decimate modifier to cut triangle count on imported or over-detailed models (a rescue tool for existing assets — new models should be modeled low-poly from the start).
• Resize textures to power-of-two, 1024×1024 or less, and repack them into the GLB.
• Delete never-visible faces (undersides, occluded backs) and enable back-face culling instead of doubling geometry.
• Merge per-color materials into a single palette-texture material, and per-part textures into one atlas.
• Strip lights, cameras, and materials on _collider meshes — dead weight the engine ignores or pays for twice.

Audit before and after with the triangle-count and material-audit scripts in the patterns file, export back to the same path (the preview hot-reloads the file), and re-check the stats panel. For a quick non-Blender pass, gltf-transform (below) can compress and strip a GLB without touching its geometry choices.

Texture Optimization

• Dimensions must be power-of-two: 256, 512, 1024
• Maximum is 1024x1024. The asset-bundle-converter enforces DESKTOPMAXTEXTURE_SIZE = 1024 (AssetBundleConverter.cs → ReduceTextureSizeIfNeeded): anything larger (e.g. 2048) is downscaled to 1024 at conversion, so authoring above 1024 wastes source size without visual benefit.
• Recommended sizes: 512x512 for most objects, 1024x1024 for hero pieces
• Use .png for UI/sprites with transparency
• Use .jpg for photos and textures without transparency
• Prefer compressed formats (WebP) over raw PNG where possible
• Use texture atlases (combine multiple textures into one image) to reduce draw calls and material count
• Share texture references across materials — do not duplicate texture files
• Reuse materials across entities:

// GOOD: Define material once, apply to many
Material.setPbrMaterial(entity1, {
	texture: Material.Texture.Common({ src: 'images/wall.jpg' }),
})
Material.setPbrMaterial(entity2, {
	texture: Material.Texture.Common({ src: 'images/wall.jpg' }),
})
// Same texture URL = shared in memory

Texture Size Guide by Use Case

Textures do not need to be square — 512x1024 is valid as long as both dimensions are powers of two.

Back-Face Culling

Back-face culling skips rendering the inside face of any polygon the player will never see from behind. It's set in your 3D modeling tool (Blender, Maya, etc.) — not in SDK code.

Rule of thumb: Enable back-face culling on all materials by default. Only disable it when a surface must be visible from both sides (e.g., a leaf plane on a tree, a thin wall).

System Optimization

Avoid Per-Frame Allocations

// BAD: Creates new Vector3 every frame
engine.addSystem(() => {
	const target = Vector3.create(8, 1, 8) // Allocation!
})

// GOOD: Reuse constants
const TARGET = Vector3.create(8, 1, 8)
engine.addSystem(() => {
	// Use TARGET
})

Throttle Expensive Operations

let lastCheck = 0
engine.addSystem((dt) => {
	lastCheck += dt
	if (lastCheck < 0.5) return // Only run every 0.5 seconds
	lastCheck = 0
	// Expensive operation here
})

Remove Systems When Not Needed

const systemFn = (dt: number) => {
	/* ... */
}
engine.addSystem(systemFn)

// When no longer needed:
engine.removeSystem(systemFn)

Asset Preloading (AssetLoad Component)

Use AssetLoad to pre-load assets into memory ahead of time so they display instantly when needed. PBAssetLoad has a single field: assets: string[] — the list of asset paths to load. Commonly created on engine.RootEntity, but any entity works.

import {
	engine,
	AssetLoad,
	assetLoadLoadingStateSystem,
	LoadingState,
} from '@dcl/sdk/ecs'

// Queue assets to pre-load (any entity works — commonly a dedicated cube/root).
// AssetLoad.getOrCreateMutable lets you also PUSH more paths later:
//   AssetLoad.getOrCreateMutable(entity, { assets: [...] }).assets.push(morePath)
AssetLoad.create(entity, { assets: ['models/big.glb', 'sounds/win.mp3'] })

// React to loading state. The callback fires PER ASSET (once per path in the
// list), receiving { asset, currentState } — NOT one batch-level event.
assetLoadLoadingStateSystem.registerAssetLoadLoadingStateEntity(
	entity,
	(state: { asset: string; currentState: LoadingState }) => {
		if (state.currentState === LoadingState.FINISHED) {
			// state.asset finished loading and is now cached
		}
	},
)
// Stop listening: assetLoadLoadingStateSystem.removeAssetLoadLoadingStateEntity(entity)

LoadingState enum members: LOADING, FINISHED, FINISHEDWITHERROR (asset found but failed to load), NOTFOUND (path does not exist), UNKNOWN (initial/default state). A missing/typo'd src resolves to NOTFOUND, not a thrown error.

Caveats:

• The state callback is per-asset, keyed by the asset path string — dispatch on state.asset to update the right entity. There is no single "all finished" event; track completion yourself by counting per-asset FINISHED/error states.
• AssetLoad only adds assets to memory. Removing a path from the assets list does not free memory — there is no unload via AssetLoad.
• Preloading a path does not create/render anything — you still getOrCreateMutable the real component (GltfContainer, AudioSource, VideoPlayer, Material texture) on an entity to use it; the preload just makes that later use instant.
• If an asset is used immediately at scene startup, there is no need for AssetLoad. Only pre-load assets NOT required at startup — things that appear later or on player interaction.

Local Asset Bundle Preview

Reproduce the server-side asset bundle conversion locally before publishing. This catches conversion issues (missing textures, broken models after compression) and makes the preview render with production-quality optimized models.

• Creator Hub: check Optimize Assets in the dropdown next to the Preview button.
• CLI: npm run start -- --local-ab

The Desktop Explorer converts all .gltf/.glb models to asset bundles on your machine. The first run may take several minutes on large scenes; converted models are cached, so subsequent previews only reconvert new or modified assets. If an asset fails to convert, the preview falls back to the raw model. Only available with the Desktop Client (not Bevy Web).

This is the local equivalent of the server-side conversion that runs after every publish (see the deploy-scene skill). Use it routinely before publishing, especially before live events.

Loading Time Optimization

• Use CDN URLs for large shared assets when possible

Loading Areas for Large Scenes

For scenes with many 3D models (e.g. a furnished multi-room building), avoid rendering everything at once. Use trigger areas to load and unload content as the player moves through the scene:

import { engine, Transform, GltfContainer, TriggerArea, triggerAreaEventsSystem, ColliderLayer } from '@dcl/sdk/ecs'
import { Vector3 } from '@dcl/sdk/math'

// Keep furniture hidden initially
let furnitureLoaded = false

// When player enters the building, spawn interior furniture
const trigger = engine.addEntity()
Transform.create(trigger, {
  position: Vector3.create(8, 1, 8),
  scale: Vector3.create(3, 3, 3)
})
TriggerArea.setBox(trigger, ColliderLayer.CL_PLAYER)

triggerAreaEventsSystem.onTriggerEnter(trigger, () => {
  if (!furnitureLoaded) loadInterior()
  furnitureLoaded = true
})
triggerAreaEventsSystem.onTriggerExit(trigger, () => {
  if (furnitureLoaded) unloadInterior()
  furnitureLoaded = false
})

This pattern keeps the initial triangle and entity counts low and loads detail only when needed.

Common Performance Pitfalls

Scene Statistics Monitoring

In Preview Mode

When running the scene locally with npm run start:

• Press P to toggle the performance panel.
• Monitor: FPS, draw calls, triangles, entities, materials, textures, memory.
• Scene limits are shown alongside current usage with green/yellow/red indicators.

What to Watch

• FPS below 30: Something is too expensive. Check draw calls and system execution time.
• Triangle count approaching limit: Enable LOD, reduce model detail, remove hidden faces.
• Entity count climbing: Likely a leak — entities being created but never destroyed. Implement pooling.
• Draw calls above 300 (1 parcel): Too many material slots being rendered. Atlas and reduce transparency to cut slots per object, and reduce the number of rendered objects. Note that draw count tracks rendered objects × their material slots — reusing one model across many entities does not reduce it (see Repeated Models above), and neither does packing many separate objects into a single .glb.

Recommended Optimization Tools

# Optimize a GLB with Draco compression
npx @gltf-transform/cli optimize input.glb output.glb --compress draco

Example scenes

Engine-team stress-test scenes (treat as ground truth for API shape):

• https://github.com/decentraland/sdk7-test-scenes/tree/main/scenes/0,2-cube-wave-32x32 — ~961 primitive cubes in ONE parcel (far over the 200-entity soft limit), all Transform.position.y mutated every frame via a single engine.getEntitiesWith(MeshRenderer) query. Demonstrates that soft limits can be exceeded and that a per-frame query over hundreds of entities is the intended pattern (no pooling needed for a fixed static set — cubes are created once in main(), not per frame).
• https://github.com/decentraland/sdk7-test-scenes/tree/main/scenes/73,-2-dbmonster — UI stress test: dozens of nested <Label> in a ReactEcs tree rebuilt every frame with Math.random() values. Demonstrates the UI render function re-runs each frame, so heavy per-frame allocation in .tsx is a real cost.
• https://github.com/decentraland/sdk7-test-scenes/tree/main/scenes/88,-12-asset-load — AssetLoad preloading with the per-asset assetLoadLoadingStateSystem state callback (mp3 / texture / video / glb, plus a deliberately missing path that resolves to NOT_FOUND).
• https://github.com/decentraland/sdk7-test-scenes/tree/main/scenes/94,-10-gltf-reuse-vs-merge — benchmark: GltfContainer reuse (one .glb, N entities) vs duplicate files vs merged mesh, measuring renderer/material counts, memory, and load smoothness. Uses AssetLoad preloading and collision-mask tuning for burst spawning.

Cross-References

• deploy-scene — post-publish asset bundle conversion timing, troubleshooting, /detectabs command
• add-3d-models — model loading, colliders, file organization, and driving Blender to fix or author models (references/blender-authoring.md)
• game-design — performance budgets, design patterns, and MVP planning
• advanced-rendering — texture modes, material reuse, and LOD with VisibilityComponent
• scene-runtime — EngineInfo.sceneHidden to pause expensive systems when the scene is hidden behind fullscreen Explorer UI