Start on fixing FDK and BP voxel-size weighting factors

3 files changed, 23 insertions, 9 deletions

diff --git a/cuda/3d/cone_bp.cu b/cuda/3d/cone_bp.cu
index 02242b0..aff0834 100644
--- a/cuda/3d/cone_bp.cu
+++ b/cuda/3d/cone_bp.cu
@@ -266,7 +266,11 @@ bool ConeBP_Array(cudaPitchedPtr D_volumeData,
 {
 	bindProjDataTexture(D_projArray);
 
-	float fOutputScale = params.fOutputScale * params.fVolScaleX * params.fVolScaleY * params.fVolScaleZ;
+	float fOutputScale;
+	if (params.bFDKWeighting)
+		fOutputScale = params.fOutputScale / (params.fVolScaleX * params.fVolScaleY * params.fVolScaleZ);
+	else
+		fOutputScale = params.fOutputScale * (params.fVolScaleX * params.fVolScaleY * params.fVolScaleZ);
 
 	for (unsigned int th = 0; th < dims.iProjAngles; th += g_MaxAngles) {
 		unsigned int angleCount = g_MaxAngles;
diff --git a/cuda/3d/fdk.cu b/cuda/3d/fdk.cu
index 27357ad..0630afe 100644
--- a/cuda/3d/fdk.cu
+++ b/cuda/3d/fdk.cu
@@ -59,7 +59,7 @@ __constant__ float gC_angle[g_MaxAngles];
 // per-detector u/v shifts?
 
 
-__global__ void devFDK_preweight(void* D_projData, unsigned int projPitch, unsigned int startAngle, unsigned int endAngle, float fSrcOrigin, float fDetOrigin, float fZShift, float fDetUSize, float fDetVSize, const SDimensions3D dims)
+__global__ void devFDK_preweight(void* D_projData, unsigned int projPitch, unsigned int startAngle, unsigned int endAngle, float fSrcOrigin, float fDetOrigin, float fZShift, float fDetUSize, float fDetVSize, float fVoxSize, const SDimensions3D dims)
 {
 	float* projData = (float*)D_projData;
 	int angle = startAngle + blockIdx.y * g_anglesPerWeightBlock + threadIdx.y;
@@ -83,10 +83,17 @@ __global__ void devFDK_preweight(void* D_projData, unsigned int projPitch, unsig
 
 	float fV = (startDetectorV - 0.5f*dims.iProjV + 0.5f) * fDetVSize + fZShift;
 
-	//const float fW = fCentralRayLength;
-	//const float fW = fCentralRayLength * (M_PI / 2.0f) / (float)dims.iProjAngles;
+	// Four contributions to the weighting factors:
+	// fCentralRayLength / fRayLength   : the main FDK preweighting factor
+	// fSrcOrigin / (fDetUSize * fCentralRayLength)
+	//                                  : to adjust the filter to the det width
+	// || u v s || ^ 2                  : see cone_bp.cu, FDKWEIGHT
+	// pi / (2 * iProjAngles)           : scaling of the integral over angles
+
 	const float fW1 = fSrcOrigin * fDetUSize * fDetVSize;
-	const float fW = fCentralRayLength * fW1 * fW1 * (M_PI / 2.0f) / (float)dims.iProjAngles;
+	const float fW2 = fCentralRayLength / (fDetUSize * fSrcOrigin);
+	const float fW3 = fVoxSize * fVoxSize;
+	const float fW = fCentralRayLength * fW1 * fW1 * fW2 * fW3 * (M_PI / 2.0f) / (float)dims.iProjAngles;
 
 	for (int detectorV = startDetectorV; detectorV < endDetectorV; ++detectorV)
 	{
@@ -156,7 +163,8 @@ __global__ void devFDK_ParkerWeight(void* D_projData, unsigned int projPitch, un
 bool FDK_PreWeight(cudaPitchedPtr D_projData,
                 float fSrcOrigin, float fDetOrigin,
                 float fZShift,
-                float fDetUSize, float fDetVSize, bool bShortScan,
+                float fDetUSize, float fDetVSize, float fVoxSize,
+				bool bShortScan,
                 const SDimensions3D& dims, const float* angles)
 {
 	// The pre-weighting factor for a ray is the cosine of the angle between
@@ -168,7 +176,7 @@ bool FDK_PreWeight(cudaPitchedPtr D_projData,
 
 	int projPitch = D_projData.pitch/sizeof(float);
 
-	devFDK_preweight<<<dimGrid, dimBlock>>>(D_projData.ptr, projPitch, 0, dims.iProjAngles, fSrcOrigin, fDetOrigin, fZShift, fDetUSize, fDetVSize, dims);
+	devFDK_preweight<<<dimGrid, dimBlock>>>(D_projData.ptr, projPitch, 0, dims.iProjAngles, fSrcOrigin, fDetOrigin, fZShift, fDetUSize, fDetVSize, fVoxSize, dims);
 
 	cudaTextForceKernelsCompletion();
 
@@ -310,8 +318,9 @@ bool FDK(cudaPitchedPtr D_volumeData,
 
 
 #if 1
+	// NB: assuming cube voxels (params.fVolScaleX)
 	ok = FDK_PreWeight(D_projData, fSrcOrigin, fDetOrigin,
-	                fZShift, fDetUSize, fDetVSize,
+	                fZShift, fDetUSize, fDetVSize, params.fVolScaleX,
 	                bShortScan, dims, pfAngles);
 #else
 	ok = true;
diff --git a/cuda/3d/fdk.h b/cuda/3d/fdk.h
index 0165af9..0f8d871 100644
--- a/cuda/3d/fdk.h
+++ b/cuda/3d/fdk.h
@@ -35,7 +35,8 @@ namespace astraCUDA3d {
 bool FDK_PreWeight(cudaPitchedPtr D_projData,
                 float fSrcOrigin, float fDetOrigin,
                 float fZShift,
-                float fDetUSize, float fDetVSize, bool bShortScan,
+                float fDetUSize, float fDetVSize, float fVoxSize,
+                bool bShortScan,
                 const SDimensions3D& dims, const float* angles);
 
 bool FDK(cudaPitchedPtr D_volumeData,