Cameras and lights from a file: the source

since 0.7.0 Formats and I/O
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: document (line 23), roundtrip (line 50), scene (line 56), check (line 77).
1/// A camera and a light, written into a GLB and read back out of it.
2///
3/// Quoted by `gltf_cameras_lights.md` and shown whole in the Source tab.
4library;

6import 'package:flutter3d/flutter3d.dart';
7import 'package:flutter3d_showcase/src/demo/demo.dart';
8import 'package:vector_math/vector_math.dart';

10final class GltfCamerasLightsDemo extends ShowcaseDemo {
late final GltfAsset _readBack;

@override
void configureView(DemoContext context) {
  context.orbit
    ..distance = 3.5
    ..pitch = 0.3
    ..yaw = 0.6;
}

@override
Future<void> prepare(DemoContext context) async {
  // glTF's own `KHR_lights_punctual` and `camera` are held on a document as
  // `ModelLight` and `ModelCamera`, addressed from a node the same way a
  // surface is. This document has one of each, plus a cube to see by.
  final document = PlainModelDocument(
    surfaces: <ModelSurface>[
      ModelSurface(mesh: CuboidShape(size: Vector3.all(1.0)).build()),
    ],
    lights: <ModelLight>[
      ModelLight(
        type: ModelLightType.directional,
        color: Vector3(1.0, 0.95, 0.85),
        intensity: 2.4,
      ),
    ],
    cameras: <ModelCamera>[
      const ModelCamera(
        projection: ModelPerspectiveCamera(yfov: 0.9, znear: 0.1),
        name: 'framing',
      ),
    ],
    nodes: <ModelNode>[
      ModelNode(surfaces: <int>[0]),
      ModelNode(name: 'sun', lightIndex: 0),
      ModelNode(name: 'framing', cameraIndex: 0),
    ],
  );

  final bytes = GltfWriter(document).writeGlb();
  _readBack = await GltfLoader().load(bytes);
}

@override
Scene build(DemoContext context) {
  final scene = Scene();
  for (final ModelSurface surface in _readBack.surfaces) {
    scene.add(
      MeshNode(
        DeviceMesh.upload(context.device, surface.mesh),
        Material(baseColor: Vector4(0.7, 0.75, 0.82, 1.0), roughness: 0.6),
        name: 'cube',
      ),
    );
  }
  for (final ModelLight light in _readBack.lights) {
    scene.add(
      LightNode(name: light.name, intensity: light.intensity)
        ..setLocalForward(Vector3(-0.4, -0.9, -0.3)),
    );
  }
  return scene;
}

@override
void verify(Scene scene, FrameResult frame) {
  if (_readBack.lights.length != 1) {
    throw StateError('the light did not survive the round trip');
  }
  if (_readBack.cameras.length != 1) {
    throw StateError('the camera did not survive the round trip');
  }
  final ModelCameraProjection projection =
      _readBack.cameras.single.projection;
  if (projection is! ModelPerspectiveCamera) {
    throw StateError('the camera came back as the wrong projection');
  }
  if (frame.drawCalls < 1) {
    throw StateError('the cube was not drawn');
  }
}
92}