Export, read back, compare: the source

since 0.7.0 Formats and I/O
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: checked (line 37), validate (line 45), report (line 67), check (line 96).
1/// Write, read back, and compare: `ExportReport` and `validateGltfExport`.
2///
3/// Quoted by `export_validate.md` and shown whole in the Source tab.
4library;

6import 'package:flutter/widgets.dart';
7import 'package:flutter3d/flutter3d.dart';
8import 'package:flutter3d_showcase/src/demo/demo.dart';
9import 'package:vector_math/vector_math.dart';

11final class ExportValidateDemo extends ShowcaseDemo {
late final ExportReport _glb;
late final ExportReport _obj;
late final ExportReport _stl;
late final List<String> _boundsProblems;

final _document = PlainModelDocument(
  surfaces: <ModelSurface>[
    ModelSurface(
      mesh: CuboidShape(size: Vector3.all(1.0)).build(),
      materialIndex: 0,
    ),
  ],
  materials: <SurfaceMaterial>[
    SurfaceMaterial(baseColor: Vector4(0.5, 0.7, 0.9, 1.0)),
  ],
  // `GltfWriter` places a surface through the node graph alone, never
  // through its own transform, so a document meant to be written as glTF
  // needs at least one node naming it.
  nodes: <ModelNode>[
    ModelNode(surfaces: <int>[0]),
  ],
);

@override
Future<void> prepare(DemoContext context) async {
  // `exportChecked` writes, reads the result back through the same writer
  // and compares. A binary format like GLB is held to a tolerance of
  // `0.0`; OBJ, a decimal text format, rounds on the way out by design and
  // is checked against `ObjWriter.decimals` own precision instead.
  _glb = await exportToGlb(_document);
  _obj = await exportToObj(_document);
  _stl = await exportToStl(_document);

  // `compareModelDocuments` proves the geometry round-tripped; it says
  // nothing about whether the file's own declared bounds match the data,
  // which is a writer's own bookkeeping and not part of a document at
  // all. `validateGltfExport` checks that separately, straight off the
  // bytes.
  _boundsProblems = await validateGltfExport(_glb.files.values.first);
}

@override
Scene build(DemoContext context) => Scene()
  ..add(
    MeshNode(
      DeviceMesh.upload(context.device, _document.surfaces.single.mesh),
      Material(baseColor: Vector4(0.5, 0.7, 0.9, 1.0)),
      name: 'cube',
    ),
  )
  ..add(
    LightNode(name: 'sun', intensity: 3.0)
      ..setLocalForward(Vector3(-0.4, -1.0, -0.3)),
  );

String _line(String name, ExportReport report) =>
    '$name: ${report.isClean ? 'clean' : 'not clean'}, '
    '${report.writerWarnings.length} warning(s), '
    '${report.differences.length} difference(s)';

String _report() =>
    '${_line('glb', _glb)}\n'
    '${_line('obj', _obj)}\n'
    '${_line('stl', _stl)}\n'
    'accessor bounds: ${_boundsProblems.isEmpty ? 'match the data' : _boundsProblems.join('\n')}';

@override
Widget? customBody(BuildContext buildContext, DemoContext context) =>
    Container(
      color: const Color(0xFF14161A),
      padding: const EdgeInsets.all(24),
      alignment: Alignment.topLeft,
      child: DefaultTextStyle(
        style: const TextStyle(
          color: Color(0xFFE8E8EC),
          fontSize: 16,
          fontFamily: 'monospace',
        ),
        child: Text(_report()),
      ),
    );

@override
void verify(Scene scene, FrameResult frame) {
  if (!_glb.isClean) {
    throw StateError('the GLB round trip was not clean: $_glb');
  }
  if (_boundsProblems.isNotEmpty) {
    throw StateError('the GLB declared the wrong bounds: $_boundsProblems');
  }
  if (frame.drawCalls < 1) {
    throw StateError('the cube was not drawn');
  }
}
106}