Move all chunk data into single SSBO.

Right now this doesn't change much, but in the future this will be helpful when(if?) I get started with multidraw and putting stuff like frustum culling onto the gpu.

assets/cubyz/shaders/chunks/chunk_vertex.vs

@@ -28,7 +28,6 @@ struct FaceData {
 };
 layout(std430, binding = 3) buffer _faceData
 {
-	int voxelSize;
 	FaceData faceData[];
 };
 
@@ -46,6 +45,7 @@ layout(std430, binding = 4) buffer _voxelModels
 };
 
 uniform int time;
+uniform int voxelSize;
 
 const vec3[6] normals = vec3[6](
 	vec3(0, 1, 0),

src/chunk.zig

@@ -393,10 +393,12 @@ pub const meshing = struct {
 		@"waterFog.density": c_int,
 		time: c_int,
 		visibilityMask: c_int,
+		voxelSize: c_int,
 	} = undefined;
 	var vao: c_uint = undefined;
 	var vbo: c_uint = undefined;
 	var faces: std.ArrayList(u32) = undefined;
+	var faceData: graphics.LargeBuffer = undefined;
 
 	pub fn init() !void {
 		shader = try Shader.create("assets/cubyz/shaders/chunks/chunk_vertex.vs", "assets/cubyz/shaders/chunks/chunk_fragment.fs");
@@ -417,6 +419,7 @@ pub const meshing = struct {
 		c.glBindVertexArray(0);
 
 		faces = try std.ArrayList(u32).initCapacity(std.heap.page_allocator, 65536);
+		try faceData.init(main.globalAllocator, 64 << 20, 3);
 	}
 
 	pub fn deinit() void {
@@ -424,6 +427,7 @@ pub const meshing = struct {
 		c.glDeleteVertexArrays(1, &vao);
 		c.glDeleteBuffers(1, &vbo);
 		faces.deinit();
+		faceData.deinit();
 	}
 
 	pub fn bindShaderAndUniforms(projMatrix: Mat4f, ambient: Vec3f, time: u32) void {
@@ -452,7 +456,7 @@ pub const meshing = struct {
 		size: ChunkCoordinate,
 		chunk: std.atomic.Atomic(?*Chunk),
 		faces: std.ArrayList(u32),
-		faceData: SSBO,
+		bufferAllocation: graphics.LargeBuffer.Allocation = .{.start = 0, .len = 0},
 		coreCount: u31 = 0,
 		neighborStart: [7]u31 = [_]u31{0} ** 7,
 		vertexCount: u31 = 0,
@@ -466,12 +470,11 @@ pub const meshing = struct {
 				.size = chunkSize*pos.voxelSize,
 				.faces = std.ArrayList(u32).init(allocator),
 				.chunk = std.atomic.Atomic(?*Chunk).init(null),
-				.faceData = SSBO.init(),
 			};
 		}
 
 		pub fn deinit(self: *ChunkMesh) void {
-			self.faceData.deinit();
+			faceData.free(self.bufferAllocation) catch unreachable;
 			self.faces.deinit();
 			if(self.chunk.load(.Monotonic)) |ch| {
 				renderer.RenderStructure.allocator.destroy(ch);
@@ -508,13 +511,13 @@ pub const meshing = struct {
 				or other.typ == 0
 				or false  // TODO: Blocks.mode(other).checkTransparency(other, neighbor) // TODO: make blocks.meshes.modelIndices(other) != 0 more strict to avoid overdraw.
 				or (!std.meta.eql(block, other) and other.viewThrough())
-				or blocks.meshes.modelIndices(other) != 0);
+				or blocks.meshes.modelIndices(other) != 0
+			);
 		}
 
 		pub fn regenerateMainMesh(self: *ChunkMesh, chunk: *Chunk) !void {
 			std.debug.assert(!self.mutex.tryLock()); // The mutex should be locked when calling this function.
 			self.faces.clearRetainingCapacity();
-			try self.faces.append(chunk.pos.voxelSize);
 			var n: u32 = 0;
 			var x: u8 = 0;
 			while(x < chunkSize): (x += 1) {
@@ -582,7 +585,7 @@ pub const meshing = struct {
 					start.* -= 2;
 				}
 			} else {
-				searchStart = 1;
+				searchStart = 0;
 				searchEnd = self.coreCount;
 				self.coreCount -= 2;
 				for(self.neighborStart) |*start| {
@@ -606,7 +609,7 @@ pub const meshing = struct {
 			if(fromNeighborChunk) |neighbor| {
 				searchRange = self.faces.items[self.neighborStart[neighbor]..self.neighborStart[neighbor+1]];
 			} else {
-				searchRange = self.faces.items[1..self.coreCount];
+				searchRange = self.faces.items[0..self.coreCount];
 			}
 			var i: u32 = 0;
 			while(i < searchRange.len): (i += 2) {
@@ -699,15 +702,16 @@ pub const meshing = struct {
 						}
 					}
 				}
-				if(neighborMesh != self) neighborMesh.uploadData();
+				if(neighborMesh != self) try neighborMesh.uploadData();
 			}
 			self.chunk.load(.Monotonic).?.blocks[getIndex(x, y, z)] = newBlock;
-			self.uploadData();
+			try self.uploadData();
 		}
 
-		fn uploadData(self: *ChunkMesh) void {
+		fn uploadData(self: *ChunkMesh) !void {
-			self.vertexCount = @intCast(u31, 6*(self.faces.items.len-1)/2);
+			self.vertexCount = @intCast(u31, 6*self.faces.items.len/2);
-			self.faceData.bufferData(u32, self.faces.items);
+			try faceData.realloc(&self.bufferAllocation, @intCast(u31, 4*self.faces.items.len));
+			faceData.bufferSubData(self.bufferAllocation.start, u32, self.faces.items);
 		}
 
 		pub fn uploadDataAndFinishNeighbors(self: *ChunkMesh) !void {
@@ -772,8 +776,7 @@ pub const meshing = struct {
 						for(neighborMesh.neighborStart[1+(neighbor ^ 1)..]) |*neighborStart| {
 							neighborStart.* = neighborStart.* - (rangeEnd - rangeStart) + @intCast(u31, additionalNeighborFaces.items.len);
 						}
-						neighborMesh.vertexCount = @intCast(u31, 6*(neighborMesh.faces.items.len-1)/2);
+						try neighborMesh.uploadData();
-						neighborMesh.faceData.bufferData(u32, neighborMesh.faces.items);
 						continue;
 					}
 				}
@@ -826,7 +829,7 @@ pub const meshing = struct {
 				}
 			}
 			self.neighborStart[6] = @intCast(u31, self.faces.items.len);
-			self.uploadData();
+			try self.uploadData();
 			self.generated = true;
 		}
 
@@ -842,8 +845,8 @@ pub const meshing = struct {
 				@floatCast(f32, @intToFloat(f64, self.pos.wz) - playerPosition[2])
 			);
 			c.glUniform1i(uniforms.visibilityMask, self.visibilityMask);
-			self.faceData.bind(3);
+			c.glUniform1i(uniforms.voxelSize, self.pos.voxelSize);
-			c.glDrawElements(c.GL_TRIANGLES, self.vertexCount, c.GL_UNSIGNED_INT, null);
+			c.glDrawElementsBaseVertex(c.GL_TRIANGLES, self.vertexCount, c.GL_UNSIGNED_INT, null, self.bufferAllocation.start/8*4);
 		}
 	};
 };

src/graphics.zig

@@ -423,6 +423,122 @@ pub const SSBO = struct {
 		c.glBufferData(c.GL_SHADER_STORAGE_BUFFER, @intCast(c_long, data.len*@sizeOf(T)), data.ptr, c.GL_STATIC_DRAW);
 		c.glBindBuffer(c.GL_SHADER_STORAGE_BUFFER, 0);
 	}
+
+	pub fn createDynamicBuffer(self: SSBO, size: usize) void {
+		c.glBindBuffer(c.GL_SHADER_STORAGE_BUFFER, self.bufferID);
+		c.glBufferData(c.GL_SHADER_STORAGE_BUFFER, @intCast(c_long, size), null, c.GL_DYNAMIC_DRAW);
+		c.glBindBuffer(c.GL_SHADER_STORAGE_BUFFER, 0);
+	}
+};
+
+/// A big SSBO that is able to allocate/free smaller regions.
+pub const LargeBuffer = struct {
+	pub const Allocation = struct {
+		start: u31,
+		len: u31,
+	};
+	ssbo: SSBO,
+	freeBlocks: std.ArrayList(Allocation),
+
+	pub fn init(self: *LargeBuffer, allocator: Allocator, size: u31, binding: c_uint) !void {
+		self.ssbo = SSBO.init();
+		self.ssbo.createDynamicBuffer(size);
+		self.ssbo.bind(binding);
+
+		self.freeBlocks = std.ArrayList(Allocation).init(allocator);
+		try self.freeBlocks.append(.{.start = 0, .len = size});
+	}
+
+	pub fn deinit(self: *LargeBuffer) void {
+		self.ssbo.deinit();
+		self.freeBlocks.deinit();
+	}
+
+	fn alloc(self: *LargeBuffer, size: u31) !Allocation {
+		var smallestBlock: ?*Allocation = null;
+		for(self.freeBlocks.items) |*block, i| {
+			if(size == block.len) {
+				return self.freeBlocks.swapRemove(i);
+			}
+			if(size < block.len and if(smallestBlock) |_smallestBlock| block.len > _smallestBlock.len else true) {
+				smallestBlock = block;
+			}
+		}
+		if(smallestBlock) |block| {
+			const result = Allocation {.start = block.start, .len = size};
+			block.start += size;
+			block.len -= size;
+			return result;
+		} else return error.OutOfMemory; // TODO: Increase the buffer size.
+	}
+
+	pub fn free(self: *LargeBuffer, _allocation: Allocation) !void {
+		var allocation = _allocation;
+		if(allocation.len == 0) return;
+		for(self.freeBlocks.items) |*block, i| {
+			if(allocation.start + allocation.len == block.start) {
+				allocation.len += block.len;
+				_ = self.freeBlocks.swapRemove(i);
+				break;
+			}
+		}
+		for(self.freeBlocks.items) |*block| {
+			if(allocation.start == block.start + block.len) {
+				block.len += allocation.len;
+				return;
+			}
+		}
+		try self.freeBlocks.append(allocation);
+	}
+
+	pub fn realloc(self: *LargeBuffer, allocation: *Allocation, newSize: u31) !void {
+		if(allocation.len == 0) allocation.* = try self.alloc(newSize);
+		if(newSize == allocation.len) return;
+		if(newSize < allocation.len) {
+			const diff = allocation.len - newSize;
+			// Check if there is a free block directly after:
+			for(self.freeBlocks.items) |*block| {
+				if(allocation.start + allocation.len == block.start and block.len + allocation.len >= newSize) {
+					block.start -= diff;
+					block.len += diff;
+					allocation.len -= diff;
+					return;
+				}
+			}
+			// Create a new free block:
+			allocation.len -= diff;
+			try self.freeBlocks.append(.{.start = allocation.start + allocation.len, .len = diff});
+		} else {
+			// Check if the buffer can be extended without a problem:
+			for(self.freeBlocks.items) |*block, i| {
+				if(allocation.start + allocation.len == block.start and block.len + allocation.len >= newSize) {
+					const diff = newSize - allocation.len;
+					allocation.len += diff;
+					if(block.len != diff) {
+						block.start += diff;
+						block.len -= diff;
+					} else {
+						_ = self.freeBlocks.swapRemove(i);
+					}
+					return;
+				}
+			}
+			const oldAllocation = allocation.*;
+			allocation.* = try self.alloc(newSize);
+
+			c.glBindBuffer(c.GL_SHADER_STORAGE_BUFFER, self.ssbo.bufferID);
+			c.glCopyBufferSubData(c.GL_SHADER_STORAGE_BUFFER, c.GL_SHADER_STORAGE_BUFFER, oldAllocation.start, allocation.start, oldAllocation.len);
+			c.glBindBuffer(c.GL_SHADER_STORAGE_BUFFER, 0);
+
+			try self.free(oldAllocation);
+		}
+	}
+
+	pub fn bufferSubData(self: *LargeBuffer, offset: u31, comptime T: type, data: []T) void {
+		c.glBindBuffer(c.GL_SHADER_STORAGE_BUFFER, self.ssbo.bufferID);
+		c.glBufferSubData(c.GL_SHADER_STORAGE_BUFFER, offset, @sizeOf(T)*@intCast(c_long, data.len), data.ptr);
+		c.glBindBuffer(c.GL_SHADER_STORAGE_BUFFER, 0);
+	}
 };
 
 pub const FrameBuffer = struct {