Path-finding: the source

since 0.4.1 Simulation, audio and XR
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: brushes (line 43), bake (line 51), live (line 76), query (line 135).
1/// Where an agent can stand, baked once from the level's architecture into a
2/// lattice a step can query in one array lookup.
3///
4/// Quoted by `nav_grid.md` and shown whole in the Source tab.
5library;

7import 'dart:math' as math;

9import 'package:flutter/widgets.dart';
10import 'package:flutter3d/flutter3d.dart';
11import 'package:flutter3d_showcase/src/demo/demo.dart';
12import 'package:flutter3d_sim/flutter3d_sim.dart';
13import 'package:vector_math/vector_math.dart';

15final class NavGridDemo extends ShowcaseDemo {
late final NavGrid _grid;

bool sweeping = true;
double _clock = 0.0;

/// Where the probe is, in metres.
final Vector2 _probe = Vector2(2.0, 2.0);

@override
Scene build(DemoContext context) {
  _grid = _bake();
  final material = Material(
    name: 'floor',
    baseColor: Vector4(0.5, 0.55, 0.6, 1.0),
  );
  final node = MeshNode(
    DeviceMesh.upload(context.device, SphereShape(segments: 16).build()),
    material,
  );
  return Scene()
    ..add(node)
    ..add(
      LightNode(name: 'sun', intensity: 3.0)
        ..setLocalForward(Vector3(-0.4, -1.0, -0.3)),
    );
}

/// Two floor slabs joined by a narrow bridge, so most of the gap between
/// them is not walkable but the bridge is.
static List<Brush> _brushes() => <Brush>[
  Brush(centre: Vector3(2, 0, 2), size: Vector3(4, 1, 4)),
  Brush(centre: Vector3(5.5, 0, 3.5), size: Vector3(3, 1, 1)),
  Brush(centre: Vector3(9, 0, 2), size: Vector3(4, 1, 4)),
];

static NavGrid _bake() => NavGrid.bake(_brushes(), cellSize: 0.5);

@override
void update(DemoContext context, double dt) {
  _clock += dt;
  if (sweeping) {
    // Across both slabs and the gap between, and over the edge.
    _probe.setValues(
      5.5 + 5.5 * math.sin(_clock * 0.5),
      2.4 + 2.2 * math.sin(_clock * 0.83 + 1.0),
    );
  }
}

@override
List<DemoControl> controls(DemoContext context) => <DemoControl>[
  ToggleControl(
    'Sweep the probe',
    value: () => sweeping,
    onChanged: (bool v) => sweeping = v,
  ),
];

@override
Widget? customBody(BuildContext buildContext, DemoContext context) {
  // Asking the baked grid about one point: which cell it falls in, and
  // whether an agent could stand there.
  final int cell = _grid.cellAtPoint(_probe.x, _probe.y);
  final bool walkable = _grid.isWalkable(cell);
  return ColoredBox(
    color: const Color(0xFF14161A),
    child: Padding(
      padding: const EdgeInsets.all(24),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Text(
            'probe at (${_probe.x.toStringAsFixed(1)}, '
            '${_probe.y.toStringAsFixed(1)}): '
            '${walkable ? 'walkable' : 'not walkable'}. Tap the map to '
            'put it somewhere.',
            style: const TextStyle(color: Color(0xFFE8E8EC), fontSize: 15),
          ),
          const SizedBox(height: 16),
          Expanded(
            child: Center(
              child: AspectRatio(
                aspectRatio: _grid.columns / _grid.rows,
                child: LayoutBuilder(
                  builder: (BuildContext context, BoxConstraints box) =>
                      GestureDetector(
                        onTapDown: (TapDownDetails d) {
                          sweeping = false;
                          _probe.setValues(
                            d.localPosition.dx /
                                box.maxWidth *
                                _grid.columns *
                                _grid.cellSize,
                            d.localPosition.dy /
                                box.maxHeight *
                                _grid.rows *
                                _grid.cellSize,
                          );
                        },
                        child: CustomPaint(
                          painter: _GridPainter(_grid, _probe, walkable),
                          child: const SizedBox.expand(),
                        ),
                      ),
                ),
              ),
            ),
          ),
        ],
      ),
    ),
  );
}

@override
void verify(Scene scene, FrameResult frame) {
  if (frame.drawCalls < 1) {
    throw StateError('the floor marker was not drawn');
  }
  final onFirstSlab = _grid.isWalkable(_grid.cellAtPoint(2.0, 2.0));
  final inTheGap = _grid.isWalkable(_grid.cellAtPoint(4.5, 0.5));
  final onBridge = _grid.isWalkable(_grid.cellAtPoint(5.0, 3.5));
  if (!onFirstSlab || inTheGap || !onBridge) {
    throw StateError(
      'the slabs and the bridge should be walkable and the open gap '
      'should not',
    );
  }
}
145}

147/// Draws the grid from above: light for a walkable cell, dark for not.
148final class _GridPainter extends CustomPainter {
const _GridPainter(this.grid, this.probe, this.walkable);

final NavGrid grid;
final Vector2 probe;
final bool walkable;

@override
void paint(Canvas canvas, Size size) {
  final cellW = size.width / grid.columns;
  final cellH = size.height / grid.rows;
  final paint = Paint();
  for (var index = 0; index < grid.cellCount; index++) {
    final cx = grid.cellX(index);
    final cz = grid.cellZ(index);
    paint.color = grid.isWalkable(index)
        ? const Color(0xFF7FB0FF)
        : const Color(0xFF2A2C33);
    canvas.drawRect(
      Rect.fromLTWH(cx * cellW, cz * cellH, cellW, cellH),
      paint,
    );
  }
  final Offset at = Offset(
    probe.x / grid.cellSize * cellW,
    probe.y / grid.cellSize * cellH,
  );
  canvas.drawCircle(
    at,
    cellW * 1.6,
    Paint()
      ..color = walkable ? const Color(0xFF6CE07C) : const Color(0xFFE5665A),
  );
}

@override
bool shouldRepaint(covariant _GridPainter oldDelegate) => true;
185}