From 849f635d04cbc0420103fc05bdb6441e83fd6251 Mon Sep 17 00:00:00 2001
From: David Williams <david@david-williams.info>
Date: Sat, 7 Jun 2008 21:21:14 +0000
Subject: [PATCH] Almost finished new marching cubes implementation. Just
 normal calculation and memory pool still to do.

---
 source/SurfaceExtractors.cpp | 141 ++++++++++++++++++++++++++++++-----
 1 file changed, 123 insertions(+), 18 deletions(-)

diff --git a/source/SurfaceExtractors.cpp b/source/SurfaceExtractors.cpp
index 1a6fea56..8b50261d 100644
--- a/source/SurfaceExtractors.cpp
+++ b/source/SurfaceExtractors.cpp
@@ -149,27 +149,132 @@ namespace PolyVox
 			const uint16_t x = volIter.getPosX() - offset.getX();
 			const uint16_t y = volIter.getPosY() - offset.getY();
 
-			//Voxels values
-			const uint8_t v000 = volIter.getVoxel();
-			const uint8_t v100 = volIter.peekVoxel1px0py0pz();
-			const uint8_t v010 = volIter.peekVoxel0px1py0pz();
-			const uint8_t v110 = volIter.peekVoxel1px1py0pz();
-			const uint8_t v001 = volIter.peekVoxel0px0py1pz();
-			const uint8_t v101 = volIter.peekVoxel1px0py1pz();
-			const uint8_t v011 = volIter.peekVoxel0px1py1pz();
-			const uint8_t v111 = volIter.peekVoxel1px1py1pz();
-
 			//Determine the index into the edge table which tells us which vertices are inside of the surface
 			uint8_t iCubeIndex = 0;
 
-			if (v000 == 0) iCubeIndex |= 1;
-			if (v100 == 0) iCubeIndex |= 2;
-			if (v110 == 0) iCubeIndex |= 4;
-			if (v010 == 0) iCubeIndex |= 8;
-			if (v001 == 0) iCubeIndex |= 16;
-			if (v101 == 0) iCubeIndex |= 32;
-			if (v111 == 0) iCubeIndex |= 64;
-			if (v011 == 0) iCubeIndex |= 128;
+			if((x==0) && (y==0))
+			{
+				const uint8_t v000 = volIter.getVoxel();
+				const uint8_t v100 = volIter.peekVoxel1px0py0pz();
+				const uint8_t v010 = volIter.peekVoxel0px1py0pz();
+				const uint8_t v110 = volIter.peekVoxel1px1py0pz();
+
+				const uint8_t v001 = volIter.peekVoxel0px0py1pz();
+				const uint8_t v101 = volIter.peekVoxel1px0py1pz();
+				const uint8_t v011 = volIter.peekVoxel0px1py1pz();
+				const uint8_t v111 = volIter.peekVoxel1px1py1pz();			
+
+				if (v000 == 0) iCubeIndex |= 1;
+				if (v100 == 0) iCubeIndex |= 2;
+				if (v110 == 0) iCubeIndex |= 4;
+				if (v010 == 0) iCubeIndex |= 8;
+				if (v001 == 0) iCubeIndex |= 16;
+				if (v101 == 0) iCubeIndex |= 32;
+				if (v111 == 0) iCubeIndex |= 64;
+				if (v011 == 0) iCubeIndex |= 128;
+			}
+			else if((x>0) && y==0)
+			{
+				const uint8_t v100 = volIter.peekVoxel1px0py0pz();
+				const uint8_t v110 = volIter.peekVoxel1px1py0pz();
+
+				const uint8_t v101 = volIter.peekVoxel1px0py1pz();
+				const uint8_t v111 = volIter.peekVoxel1px1py1pz();			
+
+				//x
+				uint8_t iPreviousCubeIndexX = bitmask[getIndex(x-1,y)];
+				uint8_t srcBit6 = iPreviousCubeIndexX & 64;
+				uint8_t destBit7 = srcBit6 << 1;
+				
+				uint8_t srcBit5 = iPreviousCubeIndexX & 32;
+				uint8_t destBit4 = srcBit5 >> 1;
+
+				uint8_t srcBit2 = iPreviousCubeIndexX & 4;
+				uint8_t destBit3 = srcBit2 << 1;
+				
+				uint8_t srcBit1 = iPreviousCubeIndexX & 2;
+				uint8_t destBit0 = srcBit1 >> 1;
+
+				iCubeIndex |= destBit0;
+				if (v100 == 0) iCubeIndex |= 2;
+				if (v110 == 0) iCubeIndex |= 4;
+				iCubeIndex |= destBit3;
+				iCubeIndex |= destBit4;
+				if (v101 == 0) iCubeIndex |= 32;
+				if (v111 == 0) iCubeIndex |= 64;
+				iCubeIndex |= destBit7;
+			}
+			else if((x==0) && (y>0))
+			{
+				const uint8_t v010 = volIter.peekVoxel0px1py0pz();
+				const uint8_t v110 = volIter.peekVoxel1px1py0pz();
+
+				const uint8_t v011 = volIter.peekVoxel0px1py1pz();
+				const uint8_t v111 = volIter.peekVoxel1px1py1pz();
+
+				//y
+				uint8_t iPreviousCubeIndexY = bitmask[getIndex(x,y-1)];
+				uint8_t srcBit7 = iPreviousCubeIndexY & 128;
+				uint8_t destBit4 = srcBit7 >> 3;
+				
+				uint8_t srcBit6 = iPreviousCubeIndexY & 64;
+				uint8_t destBit5 = srcBit6 >> 1;
+
+				uint8_t srcBit3 = iPreviousCubeIndexY & 8;
+				uint8_t destBit0 = srcBit3 >> 3;
+				
+				uint8_t srcBit2 = iPreviousCubeIndexY & 4;
+				uint8_t destBit1 = srcBit2 >> 1;
+
+				iCubeIndex |= destBit0;
+				iCubeIndex |= destBit1;
+				if (v110 == 0) iCubeIndex |= 4;
+				if (v010 == 0) iCubeIndex |= 8;
+				iCubeIndex |= destBit4;
+				iCubeIndex |= destBit5;
+				if (v111 == 0) iCubeIndex |= 64;
+				if (v011 == 0) iCubeIndex |= 128;
+			}
+			else
+			{
+				//const uint8_t v000 = volIter.getVoxel();
+				//const uint8_t v100 = volIter.peekVoxel1px0py0pz();
+				//const uint8_t v010 = volIter.peekVoxel0px1py0pz();
+				const uint8_t v110 = volIter.peekVoxel1px1py0pz();
+
+				const uint8_t v111 = volIter.peekVoxel1px1py1pz();
+
+				//y
+				uint8_t iPreviousCubeIndexY = bitmask[getIndex(x,y-1)];
+				uint8_t srcBit7 = iPreviousCubeIndexY & 128;
+				uint8_t destBit4 = srcBit7 >> 3;
+				
+				uint8_t srcBit6 = iPreviousCubeIndexY & 64;
+				uint8_t destBit5 = srcBit6 >> 1;
+
+				uint8_t srcBit3 = iPreviousCubeIndexY & 8;
+				uint8_t destBit0 = srcBit3 >> 3;
+				
+				uint8_t srcBit2 = iPreviousCubeIndexY & 4;
+				uint8_t destBit1 = srcBit2 >> 1;
+
+				//x
+				uint8_t iPreviousCubeIndexX = bitmask[getIndex(x-1,y)];
+				srcBit6 = iPreviousCubeIndexX & 64;
+				uint8_t destBit7 = srcBit6 << 1;
+
+				srcBit2 = iPreviousCubeIndexX & 4;
+				uint8_t destBit3 = srcBit2 << 1;
+
+				iCubeIndex |= destBit0;
+				iCubeIndex |= destBit1;
+				if (v110 == 0) iCubeIndex |= 4;
+				iCubeIndex |= destBit3;
+				iCubeIndex |= destBit4;
+				iCubeIndex |= destBit5;
+				if (v111 == 0) iCubeIndex |= 64;
+				iCubeIndex |= destBit7;
+			}
 
 			//Save the bitmask
 			bitmask[getIndex(x,y)] = iCubeIndex;