From f76be64d6bed96207c68136c501d8739bae73940 Mon Sep 17 00:00:00 2001
From: David Williams <david@david-williams.info>
Date: Sun, 27 Jan 2013 22:02:13 +0100
Subject: [PATCH] Work on VolumeResampler (using real convolution).

---
 .../include/PolyVoxCore/Impl/Utility.h        |  2 ++
 .../include/PolyVoxCore/VolumeResampler.inl   | 33 ++++++++++++++++---
 library/PolyVoxCore/source/Impl/Utility.cpp   |  5 +++
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/library/PolyVoxCore/include/PolyVoxCore/Impl/Utility.h b/library/PolyVoxCore/include/PolyVoxCore/Impl/Utility.h
index 5b2e327c..1b635841 100644
--- a/library/PolyVoxCore/include/PolyVoxCore/Impl/Utility.h
+++ b/library/PolyVoxCore/include/PolyVoxCore/Impl/Utility.h
@@ -54,6 +54,8 @@ namespace PolyVox
 	{
 		return (std::min)(high, (std::max)(low, value));
 	}
+
+	float triangleFilter(float fInput);
 }
 
 #endif
diff --git a/library/PolyVoxCore/include/PolyVoxCore/VolumeResampler.inl b/library/PolyVoxCore/include/PolyVoxCore/VolumeResampler.inl
index f4abc452..eb9198b3 100644
--- a/library/PolyVoxCore/include/PolyVoxCore/VolumeResampler.inl
+++ b/library/PolyVoxCore/include/PolyVoxCore/VolumeResampler.inl
@@ -23,6 +23,8 @@ freely, subject to the following restrictions:
 
 #include "PolyVoxCore/Interpolation.h"
 
+#include "PolyVoxCore/Impl/Utility.h"
+
 #include <cmath>
 
 namespace PolyVox
@@ -200,9 +202,9 @@ namespace PolyVox
 					float sy = (ty          ) + m_regSrc.getLowerCorner().getY();
 					float sz = (tz          ) + m_regSrc.getLowerCorner().getZ();
 
-					//typename SrcVolumeType::VoxelType result = m_pVolSrc->getVoxelWithWrapping(sx, sy, sz, WrapModes::Border);
+					typename SrcVolumeType::VoxelType result = m_pVolSrc->getVoxelWithWrapping(sx, sy, sz, WrapModes::Border);
 
-					typename SrcVolumeType::VoxelType result = interpolatedSample(m_pVolSrc, sx, sy, sz, WrapModes::Border, SrcVolumeType::VoxelType(0));
+					//typename SrcVolumeType::VoxelType result = interpolatedSample(m_pVolSrc, sx, sy, sz, WrapModes::Border, SrcVolumeType::VoxelType(0));
 
 					volDownscaledX.setVoxelAt(tx, ty, tz, result);
 				}
@@ -241,11 +243,32 @@ namespace PolyVox
 				{
 					float sx = (tx - m_regDst.getLowerX());
 					float sy = (ty - m_regDst.getLowerY());
-					float sz = (tz - m_regDst.getLowerZ()) * fScaleZ;
+					float sLowerZ = ((tz - 1) - m_regDst.getLowerZ()) * fScaleZ;
+					float sCentreZ = ((tz   ) - m_regDst.getLowerZ()) * fScaleZ;
+					float sUpperZ = ((tz + 1) - m_regDst.getLowerZ()) * fScaleZ;
 
-					typename SrcVolumeType::VoxelType result = volDownscaledXAndY.getVoxelWithWrapping(sx, sy, sz, WrapModes::Border);
+					float sumOfWeights = 0.0f;
+					//typename SrcVolumeType::VoxelType tSum = SrcVolumeType::VoxelType(0);
 
-					m_pVolDst->setVoxelAt(tx, ty, tz, result);
+					//We should be able to use a higher range MultiMaterial rather than needing to use a Vector of floats.
+					//We shouold also probably support an Accumulation type rather than hard coding.
+					Vector<4, float> vecSum(0.0, 0.0, 0.0, 0.0);
+
+					for(float sz = sLowerZ; sz <= sUpperZ; sz += 1.0)
+					{
+						float weight = triangleFilter(sz - sCentreZ);
+						sumOfWeights += weight;
+
+						Vector<4, float> sample = interpolatedSample(&volDownscaledXAndY, sx, sy, sz, WrapModes::Border, SrcVolumeType::VoxelType(0));
+
+						vecSum += (sample * weight);
+					}
+
+					vecSum /= sumOfWeights; //Should divide by 'norm'
+
+					typename SrcVolumeType::VoxelType tResult = vecSum; //Should divide by 'norm'
+
+					m_pVolDst->setVoxelAt(tx, ty, tz, tResult);
 				}
 			}
 		}
diff --git a/library/PolyVoxCore/source/Impl/Utility.cpp b/library/PolyVoxCore/source/Impl/Utility.cpp
index bce4cd98..4733f57f 100644
--- a/library/PolyVoxCore/source/Impl/Utility.cpp
+++ b/library/PolyVoxCore/source/Impl/Utility.cpp
@@ -73,4 +73,9 @@ namespace PolyVox
 		v++;
 		return v;
 	}
+
+	float triangleFilter(float fInput)
+	{
+		return (std::max)(1.0f - (std::abs)(fInput), 0.0f);
+	}
 }