Many copies in one draw: the source

since 0.2.0 Scene and geometry
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: batch (line 28), instances (line 47), scene (line 67), motion (line 80), check (line 98).
1/// Sixty-four coloured copies stored in one `InstancedMeshNode`.
2library;

4import 'dart:math' as math;

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

10final class InstancingDemo extends ShowcaseDemo {
static const int instanceCount = 64;

double rotationSpeed = 0.25;
double _angle = 0.0;

late final InstancedMeshNode _field;

@override
void configureView(DemoContext context) {
  context.orbit
    ..distance = 16.0
    ..pitch = 0.52
    ..yaw = 0.55;
}

@override
Scene build(DemoContext context) {
  _field = InstancedMeshNode(
    DeviceMesh.upload(
      context.device,
      const CapsuleShape(
        radius: 0.28,
        height: 0.55,
        segments: 20,
        rings: 6,
      ).build(),
    ),
    Material(
      name: 'instance material',
      baseColor: Vector4(1.0, 1.0, 1.0, 1.0),
      roughness: 0.48,
    ),
    capacity: instanceCount,
    name: 'capsule field',
  );

  const int side = 8;
  for (var i = 0; i < instanceCount; i++) {
    final int x = i % side;
    final int z = i ~/ side;
    final double height = 0.7 + 0.3 * math.sin(x * 0.9 + z * 0.65);
    final Matrix4 transform = Matrix4.identity()
      ..setTranslationRaw((x - 3.5) * 1.35, height, (z - 3.5) * 1.35)
      ..rotateY((x + z) * 0.24)
      ..scaleByDouble(1.0, 0.85 + height * 0.2, 1.0, 1.0);
    _field.addInstance(
      transform,
      color: Vector4(
        0.3 + x / 12.0,
        0.32 + z / 13.0,
        0.78 - (x + z) / 36.0,
        1.0,
      ),
    );
  }

  final Scene scene = Scene()
    ..ambientColor = Vector3(0.45, 0.52, 0.68)
    ..ambientIntensity = 0.13
    ..add(_field)
    ..add(
      LightNode(name: 'sun', intensity: 3.2)
        ..setLocalForward(Vector3(-0.5, -0.8, -0.32)),
    );
  return scene;
}

@override
void update(DemoContext context, double dt) {
  _angle = (_angle + dt * rotationSpeed) % (math.pi * 2.0);
  _field.setRotationYawPitchRoll(_angle, 0.0, 0.0);
}

@override
List<DemoControl> controls(DemoContext context) => <DemoControl>[
  SliderControl(
    'Field rotation',
    min: 0.0,
    max: 1.5,
    value: () => rotationSpeed,
    onChanged: (double value) => rotationSpeed = value,
    format: (double value) => value.toStringAsFixed(2),
  ),
];

@override
void verify(Scene scene, FrameResult frame) {
  if (_field.count != instanceCount ||
      _field.capacity < instanceCount ||
      frame.instances < instanceCount ||
      frame.drawCalls < 1) {
    throw StateError('the instanced field was not drawn');
  }
}
105}