Sheen: the source

since 0.8.0 Shading and materials
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: colours (line 26), cloth (line 35), live (line 68).
1/// Red cloth twice: bare on the left, with a sheen at its rim on the right.
2///
3/// Quoted by `sheen.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 SheenDemo extends ShowcaseDemo {
int colour = 0;
double sheenRoughness = 0.5;

static const List<String> _colourNames = <String>['Blue', 'White', 'Gold'];

late final Material _cloth;

@override
void configureView(DemoContext context) {
  context.orbit
    ..distance = 3.4
    ..yaw = 0.0
    ..pitch = 0.1;
}

/// Linear colours: the sheen is not painted, so it is not sRGB.
Vector3 _sheenColour() => switch (colour) {
  0 => Vector3(0.2, 0.4, 1.0),
  1 => Vector3(1.0, 1.0, 1.0),
  _ => Vector3(1.0, 0.75, 0.3),
};

@override
Scene build(DemoContext context) {
  final Material bare = Material(
    name: 'bare cloth',
    lighting: LightingModel.pbrLayered,
    baseColor: Vector4(0.8, 0.05, 0.05, 1.0),
    roughness: 0.6,
  );
  _cloth = Material(
    name: 'cloth with sheen',
    lighting: LightingModel.pbrLayered,
    baseColor: Vector4(0.8, 0.05, 0.05, 1.0),
    roughness: 0.6,
    extensions: MaterialExtensions(
      sheenColor: _sheenColour(),
      sheenRoughness: sheenRoughness,
    ),
  );

  final DeviceMesh ball = DeviceMesh.upload(
    context.device,
    SphereShape(radius: 0.5, segments: 48, rings: 24).build(),
  );
  return Scene()
    ..ambientIntensity = 0.15
    ..add(MeshNode(ball, bare, name: 'bare')..setPosition(-0.6, 0.0, 0.0))
    ..add(MeshNode(ball, _cloth, name: 'sheen')..setPosition(0.6, 0.0, 0.0))
    ..add(
      LightNode(name: 'key', intensity: 3.0)
        ..setLocalForward(Vector3(-0.35, -0.45, -1.0).normalized()),
    );
}

@override
void update(DemoContext context, double dt) {
  _cloth.extensions = MaterialExtensions(
    sheenColor: _sheenColour(),
    sheenRoughness: sheenRoughness,
  );
}

@override
List<DemoControl> controls(DemoContext context) => <DemoControl>[
  ChoiceControl(
    'Sheen colour',
    options: _colourNames,
    index: () => colour,
    onChanged: (int i) => colour = i,
  ),
  SliderControl(
    'Sheen roughness',
    // The shader floors sheen roughness at 0.07; below it nothing changes.
    min: 0.07,
    max: 1,
    value: () => sheenRoughness,
    onChanged: (double v) => sheenRoughness = v,
  ),
];

@override
void verify(Scene scene, FrameResult frame) {
  final MeshNode cloth = scene.meshes.firstWhere(
    (MeshNode m) => m.name == 'sheen',
  );
  if (cloth.material.extensions?.shades != true) {
    throw StateError('the cloth has no layer that changes its shading');
  }
  if (frame.drawCalls < 2) {
    throw StateError('the two spheres were not both drawn');
  }
}
104}