Creating AR Overlays in Flutter Using Sceneform

Introduction

Creating AR overlays in Flutter on Android devices requires bridging Flutter's UI with native AR libraries. Sceneform is an Android 3D framework that simplifies rendering AR content and placing virtual nodes in real space. This tutorial explains a practical integration pattern: host a Sceneform-based Android view and communicate with it from Flutter using Platform Views and MethodChannel. The approach targets flutter mobile development where you need low-latency AR overlays while keeping the Flutter UI for the rest of the app.

Setup And Dependencies

On the Android side, add Sceneform (use a maintained fork if using newer Android tooling) and ARCore dependencies to android/app/build.gradle. Ensure your Android manifest declares AR features and request CAMERA permission at runtime. Keep Flutter dependencies minimal; you will use platform views and method channels, so add no AR-specific Dart packages unless you want helpers.

Key Android-side items:

• ARCore (com.google.ar:core).

• Sceneform or Sceneform maintained fork as a Gradle dependency.

• A custom Android View or Fragment that initializes an ArSceneView and Sceneform's Renderables.

You will embed that native view into Flutter with AndroidView and control overlays by sending messages (position, text, toggle) via MethodChannel.

Sceneform Integration Strategy

The robust pattern is:

• Build a native Android component (class extends FrameLayout) that contains ArSceneView.

• Expose a simple API (createOverlay, updateOverlayPosition, removeOverlay) callable over a MethodChannel.

• Register a PlatformViewFactory to return the custom view to Flutter.

The native view should manage an AnchorNode root and a Node per overlay. When Flutter sends a position (hit test result or screen coordinates), translate it to world space and attach/update a ViewRenderable or ModelRenderable. Keep renderable creation async and cached.

On the Flutter side, instantiate an AndroidView with the registered viewType and establish a MethodChannel whose name matches the native registration. Use that channel to send JSON-like maps describing overlays.

Example Dart snippet to create an AndroidView and channel:

import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';

final channel = MethodChannel('ar_sceneform_channel');

Widget build(BuildContext context) => AndroidView(viewType: 'SceneformView');

void addOverlay(Map data) => channel.invokeMethod('addOverlay', data);

Building AR Overlays

Overlay types can be text labels, 2D widgets (ViewRenderable), or 3D models (ModelRenderable). Common overlay workflow:

1. Flutter requests a hit test for a tap. Either do hit test on native side and return results or forward the screen coordinates to Android.

2. Native side creates an Anchor at the hit location, attaches a Node, and sets a ViewRenderable for 2D UI or a ModelRenderable for 3D content.

3. When the camera moves, Sceneform manages the overlay's world-space transform so the overlay appears attached to the real surface.

When sending overlay content from Flutter, keep payloads small: use identifiers and lightweight parameters. Transfer heavier assets (e.g., textures) via URLs or preload them in the native layer. Use method channel handlers to acknowledge creation so Flutter can update local state reliably.

Example payload:

{
  "id": "overlay_1",
  "type": "label",
  "position": {"x": 0.3, "y": 0.1, "z": -1.2},
  "params": {"text": "Marker A", "scale": 0.5, "color": "#FF0000"}
}

• id: string

• type: 'label' | 'model'

• position: {x,y,z} or screenTap: {x,y}

• params: {text, scale, color, modelUrl}

Native should respond with success/failure and the world position of the attached node.

Performance And Best Practices

• Cache Renderables: Creating ModelRenderable is expensive. Preload and reuse.

• Limit Overlays: Too many active nodes hurt frame rate. Pool and reuse nodes.

• Use Simple Geometry For Labels: ViewRenderable or simple quads with textures outperform complex models for 2D overlays.

• Throttle Updates: Do not send continuous high-frequency transforms from Flutter. Let native tracking handle updates and send only control messages.

• Permission Handling: Request camera permission from Flutter or native and fail gracefully if ARCore is unsupported.

Testing tip: use the ARCore supported devices list. On emulators, use ARCore emulator images or test on physical devices for accurate results.

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Conclusion

Embedding Sceneform into a Flutter app via Platform Views gives you full native AR capabilities while preserving Flutter for the rest of the UI. The pattern—native Sceneform view, MethodChannel control, and careful resource management—delivers interactive AR overlays suitable for flutter mobile development. Prioritize caching, minimize cross-language churn, and choose the appropriate overlay types for performance. With this architecture you can iterate quickly in Dart while Sceneform handles the heavy AR rendering on Android.