From 23a56ed00082d24b6293e37e9dbdbedd233ab8bd Mon Sep 17 00:00:00 2001
From: David Williams <david@david-williams.info>
Date: Mon, 7 Feb 2011 21:34:57 +0000
Subject: [PATCH] More work on compression.

---
 examples/Basic/main.cpp                       |  6 +-
 .../PolyVoxCore/include/PolyVoxImpl/Block.h   |  2 +-
 .../PolyVoxCore/include/PolyVoxImpl/Block.inl | 72 +++++++++++--------
 library/PolyVoxCore/include/Volume.inl        |  2 +-
 4 files changed, 47 insertions(+), 35 deletions(-)

diff --git a/examples/Basic/main.cpp b/examples/Basic/main.cpp
index f591d8ed..2318d55c 100644
--- a/examples/Basic/main.cpp
+++ b/examples/Basic/main.cpp
@@ -421,7 +421,7 @@ int main(int argc, char *argv[])
 	openGLWidget.show();
 
 	//Create an empty volume and then place a sphere in it
-	Volume<MaterialDensityPair44> volData(1024, 1024, 1024);
+	Volume<MaterialDensityPair44> volData(128, 128, 128);
 	//createSphereInVolume(volData, 30);
 	createPerlinVolume(volData);
 
@@ -439,12 +439,12 @@ int main(int argc, char *argv[])
 	}*/
 
 	//Extract the surface
-	/*SurfaceMesh<PositionMaterialNormal> mesh;
+	SurfaceMesh<PositionMaterialNormal> mesh;
 	CubicSurfaceExtractorWithNormals<MaterialDensityPair44> surfaceExtractor(&volData, volData.getEnclosingRegion(), &mesh);
 	surfaceExtractor.execute();
 
 	//Pass the surface to the OpenGL window
-	openGLWidget.setSurfaceMeshToRender(mesh);*/
+	openGLWidget.setSurfaceMeshToRender(mesh);
 
 	//Run the message pump.
 	return app.exec();
diff --git a/library/PolyVoxCore/include/PolyVoxImpl/Block.h b/library/PolyVoxCore/include/PolyVoxImpl/Block.h
index 90df1e76..18d536d7 100644
--- a/library/PolyVoxCore/include/PolyVoxImpl/Block.h
+++ b/library/PolyVoxCore/include/PolyVoxImpl/Block.h
@@ -63,7 +63,7 @@ namespace PolyVox
 		bool m_bIsCompressed;
 		uint64_t m_uTimestamp;
 
-		std::vector<uint32_t> runlengths;
+		std::vector<uint8_t> runlengths;
 		std::vector<VoxelType> values;
 	};
 }
diff --git a/library/PolyVoxCore/include/PolyVoxImpl/Block.inl b/library/PolyVoxCore/include/PolyVoxImpl/Block.inl
index 27f6c862..5ccb1d14 100644
--- a/library/PolyVoxCore/include/PolyVoxImpl/Block.inl
+++ b/library/PolyVoxCore/include/PolyVoxImpl/Block.inl
@@ -27,6 +27,7 @@ freely, subject to the following restrictions:
 
 #include <cassert>
 #include <cstring> //For memcpy
+#include <limits>
 #include <stdexcept> //for std::invalid_argument
 
 namespace PolyVox
@@ -199,41 +200,37 @@ namespace PolyVox
 	template <typename VoxelType>
 	void Block<VoxelType>::compress(void)
 	{
-		VoxelType current;
-		uint32_t runLength = 0;
 		uint32_t uNoOfVoxels = m_uSideLength * m_uSideLength * m_uSideLength;
-		bool firstTime = true;
-		//uint32_t runlengthCounter = 0;
 		runlengths.clear();
 		values.clear();
 
-		for(uint32_t ct = 0; ct < uNoOfVoxels; ++ct)
+		VoxelType current = m_tUncompressedData[0];
+		uint8_t runLength = 1;
+
+		for(uint32_t ct = 1; ct < uNoOfVoxels; ++ct)
 		{		
-			VoxelType value = *(m_tUncompressedData + ct);
-			if(firstTime)
+			VoxelType value = m_tUncompressedData[ct];
+			if((value == current) && (runLength < (std::numeric_limits<uint8_t>::max)()))
 			{
-				current = value;
-				runLength = 1;
-				firstTime = false;
+				runLength++;
 			}
 			else
 			{
-				if(value == current)
-				{
-					runLength++;
-				}
-				else
-				{
-					//stream.write(reinterpret_cast<char*>(&current), sizeof(current));
-					//stream.write(reinterpret_cast<char*>(&runLength), sizeof(runLength));
-					runlengths.push_back(runLength);
-					values.push_back(current);
-					current = value;
-					runLength = 1;
-				}
-			}	
+				runlengths.push_back(runLength);
+				values.push_back(current);
+				current = value;
+				runLength = 1;
+			}
 		}
 
+		runlengths.push_back(runLength);
+		values.push_back(current);
+
+		//Shrink the vectors to their contents (seems slow?):
+		//http://stackoverflow.com/questions/1111078/reduce-the-capacity-of-an-stl-vector
+		//C++0x may have a shrink_to_fit() function?
+		//std::vector<uint8_t>(runlengths).swap(runlengths);
+		//std::vector<VoxelType>(values).swap(values);
 
 		delete[] m_tUncompressedData;
 		m_tUncompressedData = 0;
@@ -245,17 +242,32 @@ namespace PolyVox
 	{
 		m_tUncompressedData = new VoxelType[m_uSideLength * m_uSideLength * m_uSideLength];
 
-
 		VoxelType* pUncompressedData = m_tUncompressedData;
-		for(uint32_t ct = 0; ct < runlengths.size(); ++ct)
+		
+		//memset should provide the fastest way of expanding the data, but it works
+		//on unsigned chars so is only possible if our voxel type is the right size.
+		//Nore that memset takes an int type, but sonverts it to unsiogned char:
+		//http://www.cplusplus.com/reference/clibrary/cstring/memset/
+		if(sizeof(VoxelType) == sizeof(unsigned char))
 		{
-			for(uint32_t i = 0; i < runlengths[ct]; ++i)
+			for(uint32_t ct = 0; ct < runlengths.size(); ++ct)
 			{
-				*pUncompressedData = values[ct];
-				++pUncompressedData;
+				memset(pUncompressedData, *((int*)(&values[ct])), runlengths[ct]);
+				pUncompressedData += runlengths[ct];
+			}
+		}
+		//Otherwise we fall back on a loop.
+		else
+		{
+			for(uint32_t ct = 0; ct < runlengths.size(); ++ct)
+			{
+				for(uint32_t i = 0; i < runlengths[ct]; ++i)
+				{
+					*pUncompressedData = values[ct];
+					++pUncompressedData;
+				}
 			}
 		}
-
 
 		m_bIsCompressed = false;
 	}
diff --git a/library/PolyVoxCore/include/Volume.inl b/library/PolyVoxCore/include/Volume.inl
index c5905e48..db515b8b 100644
--- a/library/PolyVoxCore/include/Volume.inl
+++ b/library/PolyVoxCore/include/Volume.inl
@@ -388,7 +388,7 @@ namespace PolyVox
 			return block;
 		}
 
-		const uint32_t MaxUncompressedBlocks = 1000;
+		const uint32_t MaxUncompressedBlocks = 10;
 		if(m_pUncompressedBlocks.size() == MaxUncompressedBlocks)
 		{
 			Block<VoxelType>* pLeastRecentlyUsedBlock = 0;