Introduction

In Part 1 we created all needed methods to generate map with Grass and River. In this part we will add Forest spots to the map. A lot of code is reused from Part 1 but it is gradually enhanced step-by-step.

Final Result

The forest is added in different points and different shapes:

Implementation

Refactor previous methods

Before we start jumping into Forest, we need to enhance code written in previous part.

One of the things I did not like about it was that we directly accessed tiles list via indexes. We had to play with rows/columns/x/y variables and place them into correct spots.

With refactoring all manipulations with tiles is now done via special methods:

  MapTile tileAtPoint(Point point) {
    return tiles[point.y][point.x];
  }

  void setTileAtPoint(Point point, MapTile tile) {
    tiles[point.y][point.x] = tile;
  }

  void setTile(MapTile tile) {
    tiles[tile.y][tile.x] = tile;
  }

We no longer operate with pure x/y/row/col variables. All coordinates are instances of class Point (from dart:math).

For example, getting random point on map returns Point:

  Point _getRandomPoint() {
    var col = Random().nextInt(width - 1);
    var row = Random().nextInt(height - 1);
    return Point(col, row);
  }

With these enhancements the code looks less mathy and more OOPish.

Forest specifications

Forest can occupy empty tiles (that are currently grass)
It cannot occupy or cross the river
Forest can grow in other not yet occupied tiles.

addForest method

Implementing these requirements is pretty straightforward given that you also already wrote some useful utility functions :)


  void addForest() {
    ForestMapTile forest;

    // amount of tries to pick the spot for forest
    var tries = 10;
    while (tries-- > 0) {
      var point = _getRandomPoint();
      var tile = tileAtPoint(point);
      if (tile.type != MAP_TILE_TYPES.GRASS) {
        continue;
      }
      // first tile of the new forest spot
      forest = ForestMapTile(x: point.x, y: point.y);
      setTile(forest);

      // with 75% change grow the forest in random direction
      while (willGrow(75)) {
        var nextPoint = _nextPoint(Point(forest.x, forest.y));
        var nextTile = tileAtPoint(nextPoint);
        if (nextTile.type == MAP_TILE_TYPES.GRASS) {
          forest = ForestMapTile(x: nextPoint.x, y: nextPoint.y);
          setTileAtPoint(nextPoint, forest);
        }
      }
      // forest growing is done
      break;
    }
  }

willGrow method is enhanced and allows to provide % for success as input argument

  bool willGrow(int chance) {
    var next = Random().nextInt(100);
    return next <= chance;
  }

Another useful method is _nextPoint. It returns a nearby point to the given input point:

Point _nextPoint(Point point) {
    var decision = leftDownRight();
    var nextX = point.x;
    var nextY = point.y;
    if (decision == 0) {
      nextY = nextY + 1;
    }
    if (decision == -1) {
      nextX = nextX - 1;
    }
    if (decision == 1) {
      nextX = nextX + 1;
    }
    // truncate out of bounds values back to point inside the map
    if (nextX >= width) {
      nextX = width - 1;
    }

    if (nextY >= height) {
      nextY = height - 1;
    }

    if (nextX < 0) {
      nextX = 0;
    }

    if (nextY < 0) {
      nextY = 0;
    }

    return Point(nextX, nextY);
  }

Adding forest to the map

Another method addForests is used to generate multiple forest spots:

  void addForests() {
    width.timesRepeat(addForest);
  }

timesRepeat is an Extension for int type:

extension TimesRepeat on int {
  void timesRepeat(Function f) {
    for (var i = 0; i < this; i++) {
      f();
    }
  }
}

Create map with river and forest

Now you can call addRiver and addForests methods to initialize map:

final WorldMap map = WorldMap(width: 20, height: 20)
    ..addRiver()
    ..addForests();

The map generated map looks something like this:

In Part 3 we will generate lakes and further refactor existing functions. Stay tuned!

Generation and Render of 2D Map with Terrain in Dart + Flutter. Adding Forest Spots. Part 2

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Generation and Render of 2D Map with Terrain in Dart + Flutter. Adding Lakes. Part 3

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Introduction

Final Result

Implementation

Refactor previous methods

Forest specifications

addForest method

Adding forest to the map

Create map with river and forest

Next

Command Palette

Comments

Building game with Flutter

Generation and Render of 2D Map with Terrain in Dart + Flutter. Adding Lakes. Part 3

More from this blog

Introduction

Final Result

Implementation

Refactor previous methods

Forest specifications

addForest method

Adding forest to the map

Create map with river and forest

Next