Clustered lights: the source

since 0.8.0 Light and environment
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: floor (line 36), lights (line 49), settings (line 74).
1/// Clustered lights: every fragment is lit by the lights that reach its part
2/// of the view, so a floor under sixty-four lamps is lit by all of them.
3///
4/// Quoted by `clustered_lights.md` and shown whole in the Source tab.
5library;

7import 'dart:math' as math;

9import 'package:flutter3d/flutter3d.dart';
10import 'package:flutter3d_showcase/src/demo/demo.dart';
11import 'package:vector_math/vector_math.dart';

13final class ClusteredLightsDemo extends ShowcaseDemo {
bool clustered = true;
double range = 0.8;

final List<LightNode> _lights = <LightNode>[];

@override
void configureView(DemoContext context) {
  context.orbit
    ..distance = 9.8
    ..pitch = 1.15
    ..yaw = 0.0;
}

/// A saturated colour at [t] of the way round the hue circle.
static Vector3 _hue(double t) {
  double channel(double offset) =>
      (0.5 + 0.5 * math.cos(2 * math.pi * (t + offset))).clamp(0.0, 1.0);
  return Vector3(channel(0.0), channel(2 / 3), channel(1 / 3));
}

@override
Scene build(DemoContext context) {
  final Scene scene = Scene()
    ..ambientIntensity = 0.03
    ..add(
      MeshNode(
        DeviceMesh.upload(
          context.device,
          CuboidShape(size: Vector3(12.0, 0.1, 12.0)).build(),
        ),
        Material(name: 'floor', lighting: LightingModel.lambert),
        name: 'floor',
      )..setPosition(0.0, -0.05, 0.0),
    );

  for (var i = 0; i < 8; i++) {
    for (var j = 0; j < 8; j++) {
      final LightNode light = LightNode(
        name: 'lamp $i $j',
        type: LightType.point,
        intensity: 1.5,
        range: range,
        color: _hue((i * 8 + j) / 64.0),
      )..setPosition(i - 3.5, 0.3, j - 3.5);
      _lights.add(light);
      scene.add(light);
    }
  }
  return scene;
}

@override
void update(DemoContext context, double dt) {
  for (final LightNode light in _lights) {
    light.range = range;
  }
}

@override
RenderSettings settings(DemoContext context) => RenderSettings(
  clusteredLights: clustered,
);

@override
List<DemoControl> controls(DemoContext context) => <DemoControl>[
  ToggleControl(
    'Clustered lights',
    value: () => clustered,
    onChanged: (bool v) => clustered = v,
  ),
  SliderControl(
    'Light range',
    min: 0.4,
    max: 3.0,
    value: () => range,
    onChanged: (double v) => range = v,
    format: (double v) => '${v.toStringAsFixed(1)} m',
  ),
];

@override
void verify(Scene scene, FrameResult frame) {
  if (scene.lights.length != 64) {
    throw StateError('the grid should hold 64 lights');
  }
  if (!clustered) {
    throw StateError('the page should start with clusteredLights on');
  }
  // The per-draw list reports the same loss with the cells on or off: 64
  // lights less eight slots and a tail of twenty-four. Those 32 are the
  // lamps the floor loses without the cells.
  if (frame.lightsDropped != 32) {
    throw StateError(
      'a per-draw list should leave 32 of the 64 lamps out, '
      'the frame reports ${frame.lightsDropped}',
    );
  }
}
112}