add basic tile map lighter implementations (sky lighting only)

Blarg.GameFramework/Blarg.GameFramework.csproj

@@ -207,6 +207,8 @@
     <Compile Include="TileMap\Lighting\ITileMapLighter.cs" />
     <Compile Include="TileMap\TileMapRenderer.cs" />
     <Compile Include="TileMap\ChunkRenderer.cs" />
+    <Compile Include="TileMap\Lighting\BaseTileMapLighter.cs" />
+    <Compile Include="TileMap\Lighting\SimpleTileMapLighter.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
   <ItemGroup>

Blarg.GameFramework/TileMap/Lighting/BaseTileMapLighter.cs

@@ -0,0 +1,67 @@
+using System;
+using Blarg.GameFramework.Support;
+using Blarg.GameFramework.TileMap.Meshes;
+
+namespace Blarg.GameFramework.TileMap.Lighting
+{
+	public abstract class BaseTileMapLighter : ITileMapLighter
+	{
+		public abstract void Light(TileMap tileMap);
+
+		protected void ResetLightValues(TileMap tileMap)
+		{
+			for (int y = 0; y < tileMap.Height; ++y)
+			{
+				for (int z = 0; z < tileMap.Depth; ++z)
+				{
+					for (int x = 0; x < tileMap.Width; ++x)
+					{
+						var tile = tileMap.Get(x, y, z);
+
+						// sky lighting will be recalculated, and other types of light sources
+						// info stays as they were
+						tile.Flags = tile.Flags.ClearBit(Tile.FLAG_LIGHT_SKY);
+						tile.SkyLight = 0;
+						tile.TileLight = tileMap.AmbientLightValue;
+					}
+				}
+			}
+		}
+
+		protected void CastSkyLightDown(TileMap tileMap)
+		{
+			// go through each vertical column one at a time from top to bottom
+			for (int x = 0; x < tileMap.Width; ++x)
+			{
+				for (int z = 0; z < tileMap.Depth; ++z)
+				{
+					bool stillSkyLit = true;
+					byte currentSkyLightValue = tileMap.SkyLightValue;
+
+					for (int y = tileMap.Height - 1; y >= 0 && stillSkyLit; --y)
+					{
+						var tile = tileMap.Get(x, y, z);
+						var mesh = tileMap.TileMeshes.Get(tile);
+						if (mesh == null || (mesh != null && !mesh.IsOpaque(TileMesh.SIDE_TOP) && !mesh.IsOpaque(TileMesh.SIDE_BOTTOM)))
+						{
+							// tile is partially transparent or this tile is empty space
+							tile.Flags = tile.Flags.SetBit(Tile.FLAG_LIGHT_SKY);
+
+							if (mesh != null)
+								currentSkyLightValue = Tile.AdjustLightForTranslucency(currentSkyLightValue, mesh.Translucency);
+
+							tile.SkyLight = currentSkyLightValue;
+						}
+						else
+						{
+							// tile is present and is fully solid, sky lighting stops
+							// at the tile above this one
+							stillSkyLit = false;
+						}
+					}
+				}
+			}
+		}
+	}
+}
+

Blarg.GameFramework/TileMap/Lighting/SimpleTileMapLighter.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace Blarg.GameFramework.TileMap.Lighting
+{
+	public class SimpleTileMapLighter : BaseTileMapLighter
+	{
+		public override void Light(TileMap tileMap)
+		{
+			ResetLightValues(tileMap);
+			CastSkyLightDown(tileMap);
+		}
+	}
+}
+