A simple terrain generation algorithm implemented in flutter based off https://www.youtube.com/watch?v=IKB1hWWedMk&list=PLRqwX-V7Uu6ZiZxtDDRCi6uhfTH4FilpH&index=14

terrain_generation.dart

import 'dart:math';
import 'dart:typed_data';
import 'dart:ui' as UI;

import 'package:flutter/material.dart';
import 'package:vector_math/vector_math_64.dart' hide Colors;

final TargetPlatform platform = TargetPlatform.android;

void main() {
  runApp(App());
}

void main() {
  runApp(App());
}

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark(),
      debugShowCheckedModeBanner: false,
      home: TerrainGeneration(),
    );
  }
}

final up = Vector3(0.0, 1.0, 0.0);

class TerrainGeneration extends StatefulWidget {
  @override
  TerrainGenerationState createState() => TerrainGenerationState();
}

class TerrainGenerationState extends State<TerrainGeneration>
    with SingleTickerProviderStateMixin {
  // Fields private to this class
  AnimationController _animationController;
  final _customPaintKey = GlobalKey();
  bool _isInitialized = false;

  // Accessible in TerrainGenerationPainter.
  // There is no need to setState after updating these
  // They'll update with every vsync tick.
  int columns, rows;
  List<List<double>> terrain;
  double scale = 40.0;
  var flying = 0.0;
  final simplexNoise = SimplexNoise();

  @override
  void initState() {
    _animationController = AnimationController(
      vsync: this,
      duration: const Duration(days: 365),
    );

    // Await the build phase to be complete in order to get sizing
    Future.delayed(Duration.zero, () {
      final context = _customPaintKey.currentContext;
      final RenderBox box = context.findRenderObject();

      setup(box.size);
    });

    _animationController.forward();
    super.initState();
  }

  @override
  void dispose() {
    _animationController.dispose();

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Waves')),
      body: SizedBox.expand(
        child: AnimatedBuilder(
          animation: _animationController,
          builder: (context, __) {
            return CustomPaint(
              key: _customPaintKey,
              willChange: true,
              painter: _isInitialized
                  ? TerrainGenerationPainter(_animationController, this)
                  : null,
            );
          },
        ),
      ),
    );
  }

  void setup(Size size) {
    final width = size.width;
    // Add extra columns to help it fill the width of the screen
    columns = (width / scale).round() + 16;
    rows = (size.height / scale).round();

    terrain = List.generate(
      rows,
      (_) => List.generate(columns + 1, (_) => 0.0),
    );

    setState(() => _isInitialized = true);
  }
}

class TerrainGenerationPainter extends CustomPainter {
  const TerrainGenerationPainter(this.animation, this.state)
      : super(repaint: animation);

  final Animation<double> animation;
  final TerrainGenerationState state;

  @override
  void paint(Canvas canvas, Size size) {
    final scale = state.scale;
    state.flying -= 0.01;

    var iOff = state.flying;
    for (int i = 0; i < state.rows; i++) {
      var jOff = 0.0;
      state.terrain.add([]);
      for (int j = 0; j < state.columns; j++) {
        state.terrain[i][j] = state.simplexNoise.noise2D(iOff, jOff) * .25;
        // terrain[i][j] = random.nextDouble() * .25;
        jOff += 0.1;
      }
      iOff += 0.1;
    }

    final List<List<Vector3>> allVertices = [];
    // final List<List<Vector3>> allVertices = [];

    // To Account for all those columns I added in order to fill the space
    canvas.translate(-100, 0);

    for (int i = 0; i < state.rows; i++) {
      allVertices.add([]);

      for (int j = 0; j < state.columns - 1; j++) {
        final vertices = allVertices[i];

        vertices.add(
          Vector3(j * scale, i * scale, state.terrain[i][j]),
        );
        vertices.add(
          Vector3(j * scale, (i + 1) * scale, state.terrain[i][j + 1]),
        );
      }
    }

    final width = size.width;
    final height = size.height;

    final cameraPosition = Vector3(0, 0, 6);
    final brush = Paint()
      ..color = Colors.red
      ..style = PaintingStyle.stroke
      ..strokeWidth = 4.0;
    final lookAt = Vector3.zero();
    final cameraDistance = cameraPosition.distanceTo(lookAt);
    final aspectRatio = width / height;
    final zNearPlane = cameraDistance - 0.1;
    final zFarPlane = cameraDistance * 2;
    final fovYRadians = 0.7;

    // Build matrices to get us into an OpenGL-like coordinate space
    // bottom left corner of the screen is at (-1, -1), top right is at (1, 1)
    final toOpenGlCoords = Matrix4.compose(
      Vector3(-1.0, 1.0, 0.0),
      Quaternion.axisAngle(Vector3(1.0, 0.0, 0.0), pi),
      Vector3(2 / width, 2 / height, 1.0),
    );
    final toFlutterCoords = Matrix4.tryInvert(toOpenGlCoords);

    var modelMatrix = Matrix4.rotationX(-pi / 2.3).scaled(1.0, 4.5, 1.0);
    final viewMatrix = makeViewMatrix(cameraPosition, lookAt, up);
    final projectionMatrix = makePerspectiveMatrix(
      fovYRadians,
      aspectRatio,
      zNearPlane,
      zFarPlane,
    );

    final mvp = projectionMatrix * viewMatrix * modelMatrix;
    final flutterCompatTransform = toFlutterCoords * mvp * toOpenGlCoords;

    for (final vertices in allVertices) {
      final projected = vertices.map<Vector2>((vertex) {
        final vertexCopy = vertex.clone();
        vertexCopy.applyProjection(flutterCompatTransform);

        return Vector2(vertexCopy.x, vertexCopy.y);
      }).toList();
      final storage = _encodeVector2List(projected);

      canvas.drawVertices(
        UI.Vertices.raw(
          VertexMode.triangleStrip,
          storage,
        ),
        BlendMode.srcATop,
        brush,
      );
    }
  }

  // This is copied from dart:ui
  Int32List _encodeColorList(List<Color> colors) {
    final int colorCount = colors.length;
    final Int32List result = Int32List(colorCount);
    for (int i = 0; i < colorCount; ++i) result[i] = colors[i].value;

    return result;
  }

  // This is copied from dart:ui
  Float32List _encodeVector2List(List<Vector2> vertices) {
    final int pointCount = vertices.length;
    final Float32List result = Float32List(pointCount * 2);

    for (int i = 0; i < pointCount; ++i) {
      final int xIndex = i * 2;
      final int yIndex = xIndex + 1;
      final Vector2 point = vertices[i];
      result[xIndex] = point.x;
      result[yIndex] = point.y;
    }

    return result;
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => true;
}