Implement light propagation.

Fixes #61

src/chunk.zig

@@ -93,7 +93,7 @@ pub const Neighbors = struct { // TODO: Should this be an enum?
 };
 
 /// Gets the index of a given position inside this chunk.
-fn getIndex(x: i32, y: i32, z: i32) u32 {
+pub fn getIndex(x: i32, y: i32, z: i32) u32 {
 	std.debug.assert((x & chunkMask) == x and (y & chunkMask) == y and (z & chunkMask) == z);
 	return (@as(u32, @intCast(x)) << chunkShift) | (@as(u32, @intCast(y)) << chunkShift2) | @as(u32, @intCast(z));
 }
@@ -609,12 +609,12 @@ pub const meshing = struct {
 			const z = (wz >> mesh.chunk.voxelSizeShift) & chunkMask;
 			const index = getIndex(x, y, z);
 			return .{
-				mesh.lightingData.*[0].data[index],
-				mesh.lightingData.*[1].data[index],
-				mesh.lightingData.*[2].data[index],
-				mesh.lightingData.*[3].data[index],
-				mesh.lightingData.*[4].data[index],
-				mesh.lightingData.*[5].data[index],
+				mesh.lightingData.*[0].data[index].load(.Unordered),
+				mesh.lightingData.*[1].data[index].load(.Unordered),
+				mesh.lightingData.*[2].data[index].load(.Unordered),
+				mesh.lightingData.*[3].data[index].load(.Unordered),
+				mesh.lightingData.*[4].data[index].load(.Unordered),
+				mesh.lightingData.*[5].data[index].load(.Unordered),
 			};
 		}
 
@@ -812,9 +812,12 @@ pub const meshing = struct {
 
 		pub fn init(self: *ChunkMesh, pos: ChunkPosition, chunk: *Chunk) !void {
 			const lightingData = try main.globalAllocator.create([6]lighting.ChannelChunk);
-			for(lightingData) |*lightChunk| {
-				try lightChunk.init(chunk);
-			}
+			try lightingData[0].init(chunk, .sun_red);
+			try lightingData[1].init(chunk, .sun_green);
+			try lightingData[2].init(chunk, .sun_blue);
+			try lightingData[3].init(chunk, .red);
+			try lightingData[4].init(chunk, .green);
+			try lightingData[5].init(chunk, .blue);
 			self.* = ChunkMesh{
 				.pos = pos,
 				.size = chunkSize*pos.voxelSize,
@@ -853,7 +856,7 @@ pub const meshing = struct {
 			const prevVal = self.refCount.fetchSub(1, .Monotonic);
 			std.debug.assert(prevVal != 0);
 			if(prevVal == 1) {
-				renderer.RenderStructure.addMeshToClearList(self) catch @panic("Out of Memory");
+				renderer.RenderStructure.addMeshToClearListAndDecreaseRefCount(self) catch @panic("Out of Memory");
 			}
 		}
 
@@ -886,6 +889,8 @@ pub const meshing = struct {
 			self.mutex.lock();
 			self.opaqueMesh.reset();
 			self.transparentMesh.reset();
+			var lightEmittingBlocks = std.ArrayList([3]u8).init(main.globalAllocator);
+			defer lightEmittingBlocks.deinit();
 			var n: u32 = 0;
 			var x: u8 = 0;
 			while(x < chunkSize): (x += 1) {
@@ -894,6 +899,7 @@ pub const meshing = struct {
 					var z: u8 = 0;
 					while(z < chunkSize): (z += 1) {
 						const block = (&self.chunk.blocks)[getIndex(x, y, z)]; // ← a temporary fix to a compiler performance bug. TODO: check if this was fixed.
+						if(block.light() != 0) try lightEmittingBlocks.append(.{x, y, z});
 						if(block.typ == 0) continue;
 						// Check all neighbors:
 						for(Neighbors.iterable) |i| {
@@ -931,6 +937,10 @@ pub const meshing = struct {
 				}
 			}
 			self.mutex.unlock();
+			for(self.lightingData[3..]) |*lightingData| {
+				try lightingData.propagateLights(lightEmittingBlocks.items, true);
+			}
+			// TODO: Sunlight propagation
 			try self.finishNeighbors(false);
 		}
 
@@ -1071,7 +1081,7 @@ pub const meshing = struct {
 			self.transparentMesh.clearNeighbor(neighbor, isLod);
 		}
 
-		fn finishData(self: *ChunkMesh) !void {
+		pub fn finishData(self: *ChunkMesh) !void {
 			std.debug.assert(!self.mutex.tryLock());
 			try self.opaqueMesh.finish(self);
 			try self.transparentMesh.finish(self);
@@ -1167,7 +1177,7 @@ pub const meshing = struct {
 						try neighborMesh.uploadData();
 					} else {
 						neighborMesh.increaseRefCount();
-						try renderer.RenderStructure.addToUpdateList(neighborMesh);
+						try renderer.RenderStructure.addToUpdateListAndDecreaseRefCount(neighborMesh);
 					}
 				} else {
 					self.mutex.lock();

src/lighting.zig

@@ -1,31 +1,164 @@
 const std = @import("std");
+const Atomic = std.atomic.Value;
 
 const main = @import("root");
 const blocks = main.blocks;
 const chunk = main.chunk;
 
-const Channel = enum {
-	red,
-	green,
-	blue,
+const Channel = enum(u8) {
+	sun_red = 0,
+	sun_green = 1,
+	sun_blue = 2,
+	red = 3,
+	green = 4,
+	blue = 5,
 
 	pub fn shift(self: Channel) u5 {
 		switch(self) {
-			.red => return 16,
-			.green => return 8,
-			.blue => return 0,
+			.red, .sun_red => return 16,
+			.green, .sun_green => return 8,
+			.blue, .sun_blue => return 0,
 		}
 	}
 };
 
 pub const ChannelChunk = struct {
-	data: [chunk.chunkVolume]u8,
+	data: [chunk.chunkVolume]Atomic(u8),
 	mutex: std.Thread.Mutex,
+	ch: *chunk.Chunk,
+	channel: Channel,
 
-	pub fn init(self: *ChannelChunk, ch: *chunk.Chunk) !void {
+	pub fn init(self: *ChannelChunk, ch: *chunk.Chunk, channel: Channel) !void {
 		self.mutex = .{};
-		for(&self.data, 0..) |*val, i| {
-			val.* = if(ch.blocks[i].transparent()) 255 else 0; // TODO: Proper light propagation. This is just ambient occlusion at the moment.
+		self.ch = ch;
+		self.channel = channel;
+		@memset(&self.data, Atomic(u8).init(0));
+	}
+
+	const Entry = struct {
+		x: u5,
+		y: u5,
+		z: u5,
+		value: u8,
+
+		fn compare(_: void, a: @This(), b: @This()) std.math.Order {
+			if (a.value > b.value) return .gt;
+			if (a.value < b.value) return .lt;
+			return .eq;
+		}
+	};
+
+	fn propagateDirect(self: *ChannelChunk, lightQueue: *std.PriorityQueue(Entry, void, Entry.compare)) std.mem.Allocator.Error!void {
+		var neighborLists: [6]std.ArrayListUnmanaged(Entry) = .{.{}} ** 6;
+		defer {
+			for(&neighborLists) |*list| {
+				list.deinit(main.globalAllocator);
+			}
+		}
+
+		self.mutex.lock();
+		errdefer self.mutex.unlock();
+		while(lightQueue.removeOrNull()) |entry| {
+			const index = chunk.getIndex(entry.x, entry.y, entry.z);
+			if(entry.value <= self.data[index].load(.Unordered)) continue;
+			self.data[index].store(entry.value, .Unordered);
+			for(chunk.Neighbors.iterable) |neighbor| {
+				const nx = entry.x + chunk.Neighbors.relX[neighbor];
+				const ny = entry.y + chunk.Neighbors.relY[neighbor];
+				const nz = entry.z + chunk.Neighbors.relZ[neighbor];
+				var result: Entry = .{.x = @intCast(nx & chunk.chunkMask), .y = @intCast(ny & chunk.chunkMask), .z = @intCast(nz & chunk.chunkMask), .value = entry.value};
+				result.value -|= 8*|@as(u8, @intCast(self.ch.pos.voxelSize));
+				if(result.value == 0) continue;
+				if(nx < 0 or nx >= chunk.chunkSize or ny < 0 or ny >= chunk.chunkSize or nz < 0 or nz >= chunk.chunkSize) {
+					try neighborLists[neighbor].append(main.globalAllocator, result);
+					continue;
+				}
+				const neighborIndex = chunk.getIndex(nx, ny, nz);
+				var absorption: u8 = @intCast(self.ch.blocks[neighborIndex].absorption() >> self.channel.shift() & 255);
+				absorption *|= @intCast(self.ch.pos.voxelSize);
+				result.value -|= absorption;
+				if(result.value != 0) try lightQueue.add(result);
+			}
+		}
+		self.mutex.unlock();
+		if(main.renderer.RenderStructure.getMeshAndIncreaseRefCount(self.ch.pos)) |mesh| {
+			mesh.mutex.lock();
+			defer mesh.mutex.unlock();
+			try mesh.finishData();
+			try main.renderer.RenderStructure.addToUpdateListAndDecreaseRefCount(mesh);
+		}
+
+		for(0..6) |neighbor| {
+			if(neighborLists[neighbor].items.len == 0) continue;
+			const neighborMesh = main.renderer.RenderStructure.getNeighborAndIncreaseRefCount(self.ch.pos, self.ch.pos.voxelSize, @intCast(neighbor)) orelse continue;
+			defer neighborMesh.decreaseRefCount();
+			try neighborMesh.lightingData[@intFromEnum(self.channel)].propagateFromNeighbor(neighborLists[neighbor].items);
 		}
 	}
+
+	fn propagateFromNeighbor(self: *ChannelChunk, lights: []Entry) std.mem.Allocator.Error!void {
+		var lightQueue = std.PriorityQueue(Entry, void, Entry.compare).init(main.globalAllocator, {});
+		defer lightQueue.deinit();
+		for(lights) |entry| {
+			const index = chunk.getIndex(entry.x, entry.y, entry.z);
+			var result = entry;
+			var absorption: u8 = @intCast(self.ch.blocks[index].absorption() >> self.channel.shift() & 255);
+			absorption *|= @intCast(self.ch.pos.voxelSize);
+			result.value -|= absorption;
+			if(result.value != 0) try lightQueue.add(result);
+		}
+		try self.propagateDirect(&lightQueue);
+	}
+
+	pub fn propagateLights(self: *ChannelChunk, lights: [][3]u8, comptime checkNeighbors: bool) std.mem.Allocator.Error!void {
+		var lightQueue = std.PriorityQueue(Entry, void, Entry.compare).init(main.globalAllocator, {});
+		defer lightQueue.deinit();
+		for(lights) |pos| {
+			const index = chunk.getIndex(pos[0], pos[1], pos[2]);
+			try lightQueue.add(.{.x = @intCast(pos[0]), .y = @intCast(pos[1]), .z = @intCast(pos[2]), .value = @intCast(self.ch.blocks[index].light() >> self.channel.shift() & 255)});
+		}
+		if(checkNeighbors) {
+			for(0..6) |neighbor| {
+				const x3: i32 = if(neighbor & 1 == 0) chunk.chunkMask else 0;
+				var x1: i32 = 0;
+				while(x1 < chunk.chunkSize): (x1 += 1) {
+					var x2: i32 = 0;
+					while(x2 < chunk.chunkSize): (x2 += 1) {
+						var x: i32 = undefined;
+						var y: i32 = undefined;
+						var z: i32 = undefined;
+						if(chunk.Neighbors.relX[neighbor] != 0) {
+							x = x3;
+							y = x1;
+							z = x2;
+						} else if(chunk.Neighbors.relY[neighbor] != 0) {
+							x = x1;
+							y = x3;
+							z = x2;
+						} else {
+							x = x2;
+							y = x1;
+							z = x3;
+						}
+						const otherX = x+%chunk.Neighbors.relX[neighbor] & chunk.chunkMask;
+						const otherY = y+%chunk.Neighbors.relY[neighbor] & chunk.chunkMask;
+						const otherZ = z+%chunk.Neighbors.relZ[neighbor] & chunk.chunkMask;
+						const neighborMesh = main.renderer.RenderStructure.getNeighborAndIncreaseRefCount(self.ch.pos, self.ch.pos.voxelSize, @intCast(neighbor)) orelse continue;
+						defer neighborMesh.decreaseRefCount();
+						const neighborLightChunk = &neighborMesh.lightingData[@intFromEnum(self.channel)];
+						const index = chunk.getIndex(x, y, z);
+						const neighborIndex = chunk.getIndex(otherX, otherY, otherZ);
+						var value: u8 = neighborLightChunk.data[neighborIndex].load(.Unordered);
+						value -|= 8*|@as(u8, @intCast(self.ch.pos.voxelSize));
+						if(value == 0) continue;
+						var absorption: u8 = @intCast(self.ch.blocks[index].absorption() >> self.channel.shift() & 255);
+						absorption *|= @intCast(self.ch.pos.voxelSize);
+						value -|= absorption;
+						if(value != 0) try lightQueue.add(.{.x = @intCast(x), .y = @intCast(y), .z = @intCast(z), .value = value});
+					}
+				}
+			}
+		}
+		try self.propagateDirect(&lightQueue);
+	}
 };

src/renderer.zig

@@ -1601,14 +1601,14 @@ pub const RenderStructure = struct {
 		}
 	}
 
-	pub fn addMeshToClearList(mesh: *chunk.meshing.ChunkMesh) !void {
+	pub fn addMeshToClearListAndDecreaseRefCount(mesh: *chunk.meshing.ChunkMesh) !void {
 		std.debug.assert(mesh.refCount.load(.Monotonic) == 0);
 		mutex.lock();
 		defer mutex.unlock();
 		try clearList.append(mesh);
 	}
 
-	pub fn addToUpdateList(mesh: *chunk.meshing.ChunkMesh) !void {
+	pub fn addToUpdateListAndDecreaseRefCount(mesh: *chunk.meshing.ChunkMesh) !void {
 		std.debug.assert(mesh.refCount.load(.Monotonic) != 0);
 		mutex.lock();
 		defer mutex.unlock();