half-earth/resources/overlays/no_overlay.tres

@@ -4,3 +4,5 @@
 
 [resource]
 script = ExtResource( 1 )
+_healthy = Color( 0.0431373, 0.541176, 0.0235294, 1 )
+_depleted = Color( 0.670588, 0.572549, 0.27451, 1 )

half-earth/resources/tiles/tile_types/developed.tres

@@ -7,4 +7,4 @@ script = ExtResource( 1 )
 Name = "Developed"
 Key = 68
 Color = Color( 0.372549, 0.372549, 0.372549, 1 )
-HeatGeneration = 0.4
+HeatGeneration = 0.15

half-earth/resources/tiles/tile_types/wild.tres

@@ -1,10 +1,11 @@
 [gd_resource type="Resource" load_steps=2 format=2]
 
-[ext_resource path="res://scripts/tile/TileType.cs" type="Script" id=1]
+[ext_resource path="res://scripts/tile/Wild.cs" type="Script" id=1]
 
 [resource]
 script = ExtResource( 1 )
 Name = "Wild"
 Key = 87
-Color = Color( 0, 0.545098, 0.0196078, 1 )
+Color = Color( 0.14902, 1, 0, 0 )
-HeatGeneration = -0.2
+HeatGeneration = -0.02
+Threshold = 0.6

half-earth/scripts/HeatSystem.cs

@@ -0,0 +1,100 @@
+using Godot;
+
+public class HeatSystem
+{
+    private readonly TileGrid _tiles;
+    private readonly float _diffusionCoefficient;
+
+    private float[] _nextTemperatures = null;
+
+    public HeatSystem(TileGrid tiles, float diffusionCoefficient)
+    {
+        _tiles = tiles;
+        _diffusionCoefficient = diffusionCoefficient;
+        _nextTemperatures = new float[tiles.Count];
+    }
+
+    public void Process()
+    {
+        GenerateHeat();
+        Diffuse();
+    }
+
+
+    private float TransferHeat(float t0, float alpha, float nx, float ny, float px, float py)
+    {
+        float d2tdx2 = nx - 2 * t0 + px;
+        float d2tdy2 = ny - 2 * t0 + py;
+        return t0 + alpha * (d2tdx2 + d2tdy2);
+    }
+
+    private void GetNeighbourTemperatures(int x, int y, out float nx, out float ny, out float px, out float py)
+    {
+        // default value
+        var t = _tiles[x, y].temperature;
+
+        nx = x > 0 ? _tiles[x - 1, y].temperature : t;
+        px = x < _tiles.Size - 1 ? _tiles[x + 1, y].temperature : t;
+
+        ny = y > 0 ? _tiles[x, y - 1].temperature : t;
+        py = y < _tiles.Size - 1 ? _tiles[x, y + 1].temperature : t;
+    }
+    private void GenerateHeat()
+    {
+        for (int i = 0; i < _tiles.Count; i++)
+        {
+            var tile = _tiles[i];
+            var type = tile.type;
+            tile.temperature += type.HeatGeneration;
+            ApplyHeatDamage(ref tile);
+            _tiles[i] = tile;
+        }
+    }
+
+    private void ApplyHeatDamage(ref Tile tile)
+    {
+        if (!(tile.type is IDamageable damageable))
+            return;
+
+        var surplus = tile.temperature - damageable.Threshold;
+        if (surplus < 0)
+            return;
+
+        // TODO: parameterised balancing
+        tile.currentHealth -= surplus;
+        tile.currentHealth = Mathf.Clamp(tile.currentHealth, 0, 1);
+    }
+
+    private void Diffuse()
+    {
+        var D = _diffusionCoefficient;
+
+        for (int i = 0; i < _tiles.Count; i++)
+        {
+            float t = _tiles[i].temperature;
+
+            _tiles.MapIndex(i, out var x, out var y);
+
+            GetNeighbourTemperatures(
+                x, y,
+                out var nx,
+                out var ny,
+                out var px,
+                out var py);
+
+            var temperature = TransferHeat(t, D, nx, ny, px, py);
+
+            // TODO: what if it's really really cold out?
+            temperature = Mathf.Max(0, temperature);
+            _nextTemperatures[i] = temperature;
+        }
+
+        for (int i = 0; i < _tiles.Count; i++)
+        {
+            var tile = _tiles[i];
+            tile.temperature = _nextTemperatures[i];
+            _tiles[i] = tile;
+        }
+    }
+
+}

half-earth/scripts/WorldGrid.cs

@@ -16,13 +16,12 @@ public class WorldGrid : Node2D
     [Export]
     public float DiffusionCoefficient { get; set; } = 0.01f;
 
-    private float[] _nextValues = null;
-
     public struct TileView
     {
         public ShaderMaterial material;
     }
     private TileView[] _tileViews;
+    private HeatSystem _heat;
 
     // Called when the node enters the scene tree for the first time.
     public override void _Ready()
@@ -30,6 +29,8 @@ public class WorldGrid : Node2D
         _tileGrid = (TileGrid)_tileGridResource;
 
         GenerateCanvasItems(_tileGrid);
+
+        _heat = new HeatSystem(_tileGrid, DiffusionCoefficient);
     }
 
     #region Positioning
@@ -53,8 +54,6 @@ public class WorldGrid : Node2D
         var tile = _tileGrid[idx];
         tile.type = tileType;
         _tileGrid[x, y] = tile;
-
-        _tileViews[idx].material.SetShaderParam("lowColor", tileType.Color);
     }
     #endregion
 
@@ -76,7 +75,6 @@ public class WorldGrid : Node2D
         this.Clear();
 
         _tileViews = new TileView[grid.Count];
-        _nextValues = new float[grid.Count];
 
         for (int i = 0; i < grid.Count; i++)
         {
@@ -96,80 +94,11 @@ public class WorldGrid : Node2D
 
             TileView view = default;
             view.material = (ShaderMaterial)canvasItem.Material;
-            view.material.SetShaderParam("lowColor", _tileGrid.StartTileType.Color);
             _tileViews[i] = view;
         }
     }
 
     public ShaderMaterial GetTileMaterial(int idx) => _tileViews[idx].material;
 
-    #region Simulation
+    public void _on_Clock_OnTick(int ticks) => _heat.Process();
-    public void _on_Clock_OnTick(int ticks)
-    {
-        GenerateHeat();
-        Diffuse();
-    }
-
-    private float TransferHeat(float t0, float alpha, float nx, float ny, float px, float py)
-    {
-        float d2tdx2 = nx - 2 * t0 + px;
-        float d2tdy2 = ny - 2 * t0 + py;
-        return t0 + alpha * (d2tdx2 + d2tdy2);
-    }
-
-    private void GetNeighbourTemperatures(int x, int y, out float nx, out float ny, out float px, out float py)
-    {
-        // default value
-        var t = _tileGrid[x, y].temperature;
-
-        nx = x > 0 ? _tileGrid[x - 1, y].temperature : t;
-        px = x < _tileGrid.Size - 1 ? _tileGrid[x + 1, y].temperature : t;
-
-        ny = y > 0 ? _tileGrid[x, y - 1].temperature : t;
-        py = y < _tileGrid.Size - 1 ? _tileGrid[x, y + 1].temperature : t;
-    }
-
-    private void GenerateHeat()
-    {
-        for (int i = 0; i < _tileGrid.Count; i++)
-        {
-            var tile = _tileGrid[i];
-            var type = tile.type;
-            tile.temperature += type.HeatGeneration;
-            _tileGrid[i] = tile;
-        }
-    }
-
-    private void Diffuse()
-    {
-        var D = DiffusionCoefficient;
-
-        for (int i = 0; i < _tileGrid.Count; i++)
-        {
-            float t = _tileGrid[i].temperature;
-
-            _tileGrid.MapIndex(i, out var x, out var y);
-
-            GetNeighbourTemperatures(
-                x, y,
-                out var nx,
-                out var ny,
-                out var px,
-                out var py);
-
-            var temperature = TransferHeat(t, D, nx, ny, px, py);
-
-            // TODO: what if it's really really cold out?
-            temperature = Mathf.Max(0, temperature);
-            _nextValues[i] = temperature;
-        }
-
-        for (int i = 0; i < _tileGrid.Count; i++)
-        {
-            var tile = _tileGrid[i];
-            tile.temperature = _nextValues[i];
-            _tileGrid[i] = tile;
-        }
-    }
-    #endregion
 }

half-earth/scripts/overlays/NoOverlay.cs

@@ -2,10 +2,25 @@ using Godot;
 
 public class NoOverlay : Overlay
 {
+    [Export]
+    private Color _healthy;
+
+    [Export]
+    private Color _depleted;
+
     // in this view we want to draw tiles with their normal colour
     public override void Apply(Tile tile, ShaderMaterial material)
     {
         var type = tile.type;
+
+        if (type is Wild wild)
+        {
+            material.SetShaderParam("lowColor", _depleted);
+            material.SetShaderParam("highColor", _healthy);
+            material.SetShaderParam("t", tile.currentHealth);
+            return;
+        }
+
         material.SetShaderParam("lowColor", type.Color);
         material.SetShaderParam("t", 0);
     }

half-earth/scripts/tile/IDamageable.cs

@@ -0,0 +1,4 @@
+public interface IDamageable
+{
+    float Threshold { get; }
+}

half-earth/scripts/tile/Tile.cs

@@ -5,4 +5,5 @@ public struct Tile
     public bool isHighlighted;
     public float temperature;
     public TileType type;
+    public float currentHealth;
 }

half-earth/scripts/tile/TileGrid.cs

@@ -10,7 +10,7 @@ public class TileGrid : Resource, IReadOnlyList<Tile>
 
     [Export]
     private Resource _startTileTypeResource;
-    public TileType StartTileType => (TileType)_startTileTypeResource;
+    private TileType StartTileType => (TileType)_startTileTypeResource;
 
     public int Count => Size * Size;
 
@@ -58,6 +58,7 @@ public class TileGrid : Resource, IReadOnlyList<Tile>
             tile.isHighlighted = false;
             tile.temperature = 0.0f;
             tile.type = StartTileType;
+            tile.currentHealth = 1.0f;
 
             tiles.Add(tile);
         }

half-earth/scripts/tile/Wild.cs

@@ -0,0 +1,7 @@
+using Godot;
+
+public class Wild : TileType, IDamageable
+{
+    [Export]
+    public float Threshold { get; private set; }
+}