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authorAlexander Harkness <bearbin@gmail.com>2013-11-24 15:19:41 +0100
committerAlexander Harkness <bearbin@gmail.com>2013-11-24 15:19:41 +0100
commit675b4aa878f16291ce33fced48a2bc7425f635ae (patch)
tree409914df27a98f65adf866da669429c4de141b6f /src/LightingThread.h
parentLineBlockTracer: Using the coord-based block faces. (diff)
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+
+// LightingThread.h
+
+// Interfaces to the cLightingThread class representing the thread that processes requests for lighting
+
+/*
+Lighting is done on whole chunks. For each chunk to be lighted, the whole 3x3 chunk area around it is read,
+then it is processed, so that the middle chunk area has valid lighting, and the lighting is copied into the ChunkMap.
+Lighting is calculated in full char arrays instead of nibbles, so that accessing the arrays is fast.
+Lighting is calculated in a flood-fill fashion:
+1. Generate seeds from where the light spreads (full skylight / light-emitting blocks)
+2. For each seed:
+ - Spread the light 1 block in each of the 6 cardinal directions, if the blocktype allows
+ - If the recipient block has had lower lighting value than that being spread, make it a new seed
+3. Repeat step 2, until there are no more seeds
+The seeds need two fast operations:
+ - Check if a block at [x, y, z] is already a seed
+ - Get the next seed in the row
+For that reason it is stored in two arrays, one stores a bool saying a seed is in that position,
+the other is an array of seed coords, encoded as a single int.
+Step 2 needs two separate storages for old seeds and new seeds, so there are two actual storages for that purpose,
+their content is swapped after each full step-2-cycle.
+
+The thread has two queues of chunks that are to be lighted.
+The first queue, m_Queue, is the only one that is publicly visible, chunks get queued there by external requests.
+The second one, m_PostponedQueue, is for chunks that have been taken out of m_Queue and didn't have neighbors ready.
+Chunks from m_PostponedQueue are moved back into m_Queue when their neighbors get valid, using the ChunkReady callback.
+*/
+
+
+
+#pragma once
+
+#include "OSSupport/IsThread.h"
+#include "ChunkDef.h"
+
+
+
+
+
+// fwd: "cWorld.h"
+class cWorld;
+
+// fwd: "cChunkMap.h"
+class cChunkStay;
+
+
+
+
+
+class cLightingThread :
+ public cIsThread
+{
+ typedef cIsThread super;
+
+public:
+
+ cLightingThread(void);
+ ~cLightingThread();
+
+ bool Start(cWorld * a_World);
+
+ void Stop(void);
+
+ /// Queues the entire chunk for lighting
+ void QueueChunk(int a_ChunkX, int a_ChunkZ, cChunkCoordCallback * a_CallbackAfter = NULL);
+
+ /// Blocks until the queue is empty or the thread is terminated
+ void WaitForQueueEmpty(void);
+
+ size_t GetQueueLength(void);
+
+ /// Called from cWorld when a chunk gets valid. Chunks in m_PostponedQueue may need moving into m_Queue
+ void ChunkReady(int a_ChunkX, int a_ChunkZ);
+
+protected:
+
+ struct sItem
+ {
+ int x, z;
+ cChunkStay * m_ChunkStay;
+ cChunkCoordCallback * m_Callback;
+
+ sItem(void) {} // empty default constructor needed
+ sItem(int a_X, int a_Z, cChunkStay * a_ChunkStay, cChunkCoordCallback * a_Callback) :
+ x(a_X),
+ z(a_Z),
+ m_ChunkStay(a_ChunkStay),
+ m_Callback(a_Callback)
+ {
+ }
+ } ;
+
+ typedef std::list<sItem> sItems;
+
+ cWorld * m_World;
+ cCriticalSection m_CS;
+ sItems m_Queue;
+ sItems m_PostponedQueue; // Chunks that have been postponed due to missing neighbors
+ cEvent m_evtItemAdded; // Set when queue is appended, or to stop the thread
+ cEvent m_evtQueueEmpty; // Set when the queue gets empty
+
+ // Buffers for the 3x3 chunk data
+ // These buffers alone are 1.7 MiB in size, therefore they cannot be located on the stack safely - some architectures may have only 1 MiB for stack, or even less
+ // Placing the buffers into the object means that this object can light chunks only in one thread!
+ // The blobs are XZY organized as a whole, instead of 3x3 XZY-organized subarrays ->
+ // -> This means data has to be scatterred when reading and gathered when writing!
+ static const int BlocksPerYLayer = cChunkDef::Width * cChunkDef::Width * 3 * 3;
+ BLOCKTYPE m_BlockTypes[BlocksPerYLayer * cChunkDef::Height];
+ NIBBLETYPE m_BlockLight[BlocksPerYLayer * cChunkDef::Height];
+ NIBBLETYPE m_SkyLight [BlocksPerYLayer * cChunkDef::Height];
+ HEIGHTTYPE m_HeightMap [BlocksPerYLayer];
+
+ // Seed management (5.7 MiB)
+ // Two buffers, in each calc step one is set as input and the other as output, then in the next step they're swapped
+ // Each seed is represented twice in this structure - both as a "list" and as a "position".
+ // "list" allows fast traversal from seed to seed
+ // "position" allows fast checking if a coord is already a seed
+ unsigned char m_IsSeed1 [BlocksPerYLayer * cChunkDef::Height];
+ unsigned int m_SeedIdx1[BlocksPerYLayer * cChunkDef::Height];
+ unsigned char m_IsSeed2 [BlocksPerYLayer * cChunkDef::Height];
+ unsigned int m_SeedIdx2[BlocksPerYLayer * cChunkDef::Height];
+ int m_NumSeeds;
+
+ virtual void Execute(void) override;
+
+ /// Lights the entire chunk. If neighbor chunks don't exist, touches them and re-queues the chunk
+ void LightChunk(sItem & a_Item);
+
+ /// Prepares m_BlockTypes and m_HeightMap data; returns false if any of the chunks fail. Zeroes out the light arrays
+ bool ReadChunks(int a_ChunkX, int a_ChunkZ);
+
+ /// Uses m_HeightMap to initialize the m_SkyLight[] data; fills in seeds for the skylight
+ void PrepareSkyLight(void);
+
+ /// Uses m_BlockTypes to initialize the m_BlockLight[] data; fills in seeds for the blocklight
+ void PrepareBlockLight(void);
+
+ /// Calculates light in the light array specified, using stored seeds
+ void CalcLight(NIBBLETYPE * a_Light);
+
+ /// Does one step in the light calculation - one seed propagation and seed recalculation
+ void CalcLightStep(
+ NIBBLETYPE * a_Light,
+ int a_NumSeedsIn, unsigned char * a_IsSeedIn, unsigned int * a_SeedIdxIn,
+ int & a_NumSeedsOut, unsigned char * a_IsSeedOut, unsigned int * a_SeedIdxOut
+ );
+
+ /// Compresses from 1-block-per-byte (faster calc) into 2-blocks-per-byte (MC storage):
+ void CompressLight(NIBBLETYPE * a_LightArray, NIBBLETYPE * a_ChunkLight);
+
+ inline void PropagateLight(
+ NIBBLETYPE * a_Light,
+ int a_SrcIdx, int a_DstIdx,
+ int & a_NumSeedsOut, unsigned char * a_IsSeedOut, unsigned int * a_SeedIdxOut
+ )
+ {
+ ASSERT(a_SrcIdx >= 0);
+ ASSERT(a_SrcIdx < ARRAYCOUNT(m_SkyLight));
+ ASSERT(a_DstIdx >= 0);
+ ASSERT(a_DstIdx < ARRAYCOUNT(m_BlockTypes));
+
+ if (a_Light[a_SrcIdx] <= a_Light[a_DstIdx] + g_BlockSpreadLightFalloff[m_BlockTypes[a_DstIdx]])
+ {
+ // We're not offering more light than the dest block already has
+ return;
+ }
+
+ a_Light[a_DstIdx] = a_Light[a_SrcIdx] - g_BlockSpreadLightFalloff[m_BlockTypes[a_DstIdx]];
+ if (!a_IsSeedOut[a_DstIdx])
+ {
+ a_IsSeedOut[a_DstIdx] = true;
+ a_SeedIdxOut[a_NumSeedsOut++] = a_DstIdx;
+ }
+ }
+
+} ;
+
+
+
+