One bounce of diffuse light: the source

since 0.7.0 Light and environment
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: field (line 71), gather (line 79), live (line 84), shadow (line 90).
1/// One bounce of diffuse light: a grid of probes, each filled by casting rays
2/// out from it and recording what colour comes back.
3///
4/// Quoted by `irradiance_field.md` and shown whole in the Source tab.
5library;

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

11final class IrradianceFieldDemo extends ShowcaseDemo {
bool baked = true;
double ambient = 0.5;

late final IrradianceField _field;
late final Scene _scene;

@override
void configureView(DemoContext context) {
  context.orbit
    ..distance = 6.0
    ..pitch = 0.35
    ..yaw = 0.5;
  context.orbit.target.setValues(-0.5, 1.0, 0.0);
}

@override
Scene build(DemoContext context) {
  final Material floor = Material(
    name: 'floor',
    baseColor: Vector4(0.55, 0.55, 0.55, 1.0),
    roughness: 0.95,
    doubleSided: true,
  );
  final Material wall = Material(
    name: 'red wall',
    baseColor: Vector4(0.85, 0.08, 0.08, 1.0),
    roughness: 0.95,
    doubleSided: true,
  );

  final MeshNode wallNode =
      MeshNode(
          DeviceMesh.upload(
            context.device,
            const PlaneShape(width: 3, depth: 4).build(),
          ),
          wall,
          name: 'wall',
        )
        ..setPosition(-2.0, 1.5, 0.0)
        ..setRotation(Quaternion.axisAngle(Vector3(0.0, 0.0, 1.0), -1.5708));

  final Scene scene = _scene = Scene()
    ..add(
      MeshNode(
        DeviceMesh.upload(
          context.device,
          const PlaneShape(width: 6, depth: 6).build(),
        ),
        floor,
        name: 'floor',
      ),
    )
    ..add(wallNode)
    ..add(
      LightNode(name: 'sun', intensity: 4.0)
        ..setLocalForward(Vector3(-0.6, -0.7, 0.15)),
    );

  _field = IrradianceField(
    origin: Vector3(-1.0, 0.5, -1.0),
    spacing: Vector3(1.0, 1.0, 1.0),
    countX: 2,
    countY: 2,
    countZ: 2,
  );

  gather(_field, scene, rays: 96);

  return scene;
}

@override
void update(DemoContext context, double dt) {
  _scene.irradianceField = baked ? _field : null;
  _scene.ambientIntensity = ambient;
}

// A one-sided wall, not a closed brush. A pass that records only back
// faces sees straight through a plane like this one, so the floor beside
// the wall would never fall into shadow and the field's bounce light would
// have nothing but full sun to compete with. The sun records both sides by
// default since 0.8.2; named here because the shadow depends on it.
@override
RenderSettings settings(DemoContext context) => const RenderSettings(
  shadows: ShadowSettings(directionalCasterFaces: ShadowCasterFaces.both),
);

@override
List<DemoControl> controls(DemoContext context) => <DemoControl>[
  ToggleControl(
    'Field on',
    value: () => baked,
    onChanged: (bool v) => baked = v,
  ),
  SliderControl(
    'Ambient strength',
    min: 0,
    max: 2,
    value: () => ambient,
    onChanged: (double v) => ambient = v,
  ),
];

@override
void verify(Scene scene, FrameResult frame) {
  final Vector3 towardWall = _field.sample(
    Vector3(-0.5, 1.0, -0.5),
    Vector3(-1.0, 0.0, 0.0),
  );
  final Vector3 awayFromWall = _field.sample(
    Vector3(-0.5, 1.0, -0.5),
    Vector3(1.0, 0.0, 0.0),
  );
  if (towardWall.x < 0.01 || towardWall.x <= awayFromWall.x * 1.5) {
    throw StateError(
      'the probe facing the red wall ($towardWall) is not redder than the '
      'one facing away from it ($awayFromWall); the bounce never arrived',
    );
  }
}
133}