Procedural sky: the source

since 0.2.0 Light and environment
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: sun (line 50), dome (line 52), sky (line 100).
1/// A sky that needs no image: a gradient, a glow and a sun disc, drawn by the
2/// renderer from a few numbers.
3///
4/// Quoted by `procedural_sky.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 ProceduralSkyDemo extends ShowcaseDemo {
double sunHeight = 14.0;
double sunDisc = 6.0;
double glow = 0.4;
bool dome = false;

late final LightNode _sun;
late final MeshNode _dome;

@override
void configureView(DemoContext context) {
  context.orbit
    ..distance = 7.0
    ..pitch = 0.1
    ..yaw = 0.9;
  context.orbit.target.setValues(0.0, 0.8, 0.0);
}

// The way to the sun for the current height, at a fixed compass bearing.
Vector3 get _towardsSun {
  final double up = sunHeight * math.pi / 180.0;
  return Vector3(-math.cos(up) * 0.6, math.sin(up), -math.cos(up) * 0.8);
}

@override
Scene build(DemoContext context) {
  final Material ground = Material(
    name: 'ground',
    baseColor: Vector4(0.42, 0.4, 0.36, 1.0),
    roughness: 0.9,
    doubleSided: true,
  );
  final Material ball = Material(
    name: 'ball',
    baseColor: Vector4(0.8, 0.8, 0.82, 1.0),
    roughness: 0.35,
  );
  _sun = LightNode(name: 'sun', intensity: 3.0);

  final MeshData shell = const SkyDome().build();
  paintSky(
    shell,
    SkyGradient(
      zenith: Vector3(0.08, 0.2, 0.5),
      horizon: Vector3(0.5, 0.58, 0.68),
      nadir: Vector3(0.06, 0.06, 0.07),
    ).colour,
  );
  _dome = skyNode(DeviceMesh.upload(context.device, shell))..visible = false;

  return Scene()
    ..ambientIntensity = 0.4
    ..add(
      MeshNode(
        DeviceMesh.upload(
          context.device,
          const PlaneShape(width: 30, depth: 30).build(),
        ),
        ground,
        name: 'ground',
      ),
    )
    ..add(
      MeshNode(
        DeviceMesh.upload(
          context.device,
          SphereShape(radius: 0.8, segments: 32, rings: 16).build(),
        ),
        ball,
        name: 'ball',
      )..setPosition(0.0, 0.8, 0.0),
    )
    ..add(_sun)
    ..add(_dome);
}

@override
void update(DemoContext context, double dt) {
  _sun.setLocalForward(-_towardsSun);
  _dome.visible = dome;
  // The dome is small and has to follow the eye, or it is a ball on the
  // ground.
  followCamera(_dome, context.camera);
}

@override
RenderSettings settings(DemoContext context) => RenderSettings(
  sky: SkySettings(
    enabled: !dome,
    directionToSun: _towardsSun,
    sunIntensity: sunDisc,
    glowStrength: glow,
  ),
);

@override
List<DemoControl> controls(DemoContext context) => <DemoControl>[
  SliderControl(
    'Sun height',
    min: 2,
    max: 85,
    value: () => sunHeight,
    onChanged: (double v) => sunHeight = v,
    format: (double v) => '${v.round()} deg',
  ),
  SliderControl(
    'Sun disc',
    min: 0,
    max: 20,
    value: () => sunDisc,
    onChanged: (double v) => sunDisc = v,
  ),
  SliderControl(
    'Glow',
    min: 0,
    max: 1,
    value: () => glow,
    onChanged: (double v) => glow = v,
  ),
  ToggleControl(
    'Painted dome instead',
    value: () => dome,
    onChanged: (bool v) => dome = v,
  ),
];

@override
void verify(Scene scene, FrameResult frame) {
  final FramePass draw = frame.passes.firstWhere(
    (FramePass p) => p.name == 'scene',
  );
  final int meshes = scene.meshes.where((MeshNode m) => m.visible).length;
  // The sky is one full-screen triangle inside the scene pass, so it is the
  // draw that comes on top of the meshes.
  if (draw.drawCalls != meshes + 1) {
    throw StateError(
      'expected $meshes mesh draws and one for the sky, '
      'got ${draw.drawCalls}',
    );
  }
}
154}