Update version to 1.3

1 files changed, 739 insertions, 0 deletions

diff --git a/include/astra/ParallelBeamStripKernelProjector2D.inl b/include/astra/ParallelBeamStripKernelProjector2D.inl
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+++ b/include/astra/ParallelBeamStripKernelProjector2D.inl
@@ -0,0 +1,739 @@
+/*
+-----------------------------------------------------------------------
+Copyright 2012 iMinds-Vision Lab, University of Antwerp
+
+Contact: astra@ua.ac.be
+Website: http://astra.ua.ac.be
+
+
+This file is part of the
+All Scale Tomographic Reconstruction Antwerp Toolbox ("ASTRA Toolbox").
+
+The ASTRA Toolbox is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+The ASTRA Toolbox is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
+
+-----------------------------------------------------------------------
+$Id$
+*/
+
+
+//----------------------------------------------------------------------------------------
+// PROJECT ALL 
+template <typename Policy>
+void CParallelBeamStripKernelProjector2D::project(Policy& p)
+{
+	ASTRA_ASSERT(m_bIsInitialized);
+
+	// Some variables
+	float32 theta, t;
+	int row, col;
+	int iAngle;
+	int iDetector;
+	float32 res;
+	float32 PL, PLimitL, PLimitR;
+	float32 xL, xR, XLimitL, XLimitR;
+	int x1L,x1R;
+	float32 x2L, x2R, updateX;
+	int iVolumeIndex, iRayIndex;
+	
+	float32 sin_theta, cos_theta, inv_sin_theta, inv_cos_theta;
+	float32 fabs_sin_theta, fabs_cos_theta, fabs_inv_sin_theta, fabs_inv_cos_theta;
+	float32 PW, PH, DW, inv_PW, inv_PH;
+	float32 S, T, U, V, inv_4T;
+
+	// loop angles
+	for (iAngle = 0; iAngle < m_pProjectionGeometry->getProjectionAngleCount(); ++iAngle) {
+		
+		// get values
+		theta = m_pProjectionGeometry->getProjectionAngle(iAngle);
+		bool switch_t = false;
+		if (theta >= 7*PIdiv4) theta -= 2*PI;
+		if (theta >= 3*PIdiv4) {
+			theta -= PI;
+			switch_t = true;
+		}
+
+		// Precalculate sin, cos, 1/cos
+		sin_theta = sin(theta);
+		cos_theta = cos(theta);
+		inv_cos_theta = 1.0f / cos_theta; 
+		inv_sin_theta = 1.0f / sin_theta;
+
+		fabs_sin_theta = (sin_theta < 0.0f) ? -sin_theta : sin_theta;
+		fabs_cos_theta = (cos_theta < 0.0f) ? -cos_theta : cos_theta;
+		fabs_inv_cos_theta = (inv_cos_theta < 0.0f) ? -inv_cos_theta : inv_cos_theta;
+		fabs_inv_sin_theta = (inv_sin_theta < 0.0f) ? -inv_sin_theta : inv_sin_theta;
+
+		// Other precalculations
+		PW = m_pVolumeGeometry->getPixelLengthX();
+		PH = m_pVolumeGeometry->getPixelLengthY();
+		DW = m_pProjectionGeometry->getDetectorWidth();
+		inv_PW = 1.0f / PW;
+		inv_PH = 1.0f / PH;
+
+		// [-45?,45?] and [135?,225?]
+		if (theta < PIdiv4) {
+
+			// Precalculate kernel limits
+			S = -0.5f * fabs_sin_theta * fabs_inv_cos_theta;
+			T = -S;
+			U = 1.0f + S;
+			V = 1.0f - S;
+			inv_4T = 0.25f / T;
+
+			updateX = sin_theta * inv_cos_theta;
+
+			// loop detectors
+			for (iDetector = 0; iDetector < m_pProjectionGeometry->getDetectorCount(); ++iDetector) {
+			
+				iRayIndex = iAngle * m_pProjectionGeometry->getDetectorCount() + iDetector;
+
+				// POLICY: RAY PRIOR
+				if (!p.rayPrior(iRayIndex)) continue;
+
+				// get t
+				t = m_pProjectionGeometry->indexToDetectorOffset(iDetector);
+				if (switch_t) t = -t;
+			
+				// calculate left strip extremes (volume coordinates)
+				PL = (t - sin_theta * m_pVolumeGeometry->pixelRowToCenterY(0) - DW*0.5f) * inv_cos_theta;
+				PLimitL = PL - 0.5f * fabs_sin_theta * fabs_inv_cos_theta * PH;
+				PLimitR = PLimitL + DW * inv_cos_theta + PH * fabs_sin_theta * fabs_inv_cos_theta; 
+
+				// calculate strip extremes (pixel coordinates)
+				XLimitL = (PLimitL - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+				XLimitR = (PLimitR - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+				xL = (PL - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+				xR = xL + (DW * inv_cos_theta) * inv_PW;
+	
+				// for each row
+				for (row = 0; row < m_pVolumeGeometry->getGridRowCount(); ++row) {
+				
+					// get strip extremes in column indices
+					x1L = int((XLimitL > 0.0f) ? XLimitL : XLimitL-1.0f);
+					x1R = int((XLimitR > 0.0f) ? XLimitR : XLimitR-1.0f);
+
+					// get coords w.r.t leftmost column hit by strip
+					x2L = xL - x1L; 
+					x2R = xR - x1L;
+					
+					// update strip extremes for the next row
+					XLimitL += updateX; 
+					XLimitR += updateX;
+					xL += updateX; 
+					xR += updateX; 
+
+					// for each affected col
+					for (col = x1L; col <= x1R; ++col) {
+
+						if (col < 0 || col >= m_pVolumeGeometry->getGridColCount()) { x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+						iVolumeIndex = m_pVolumeGeometry->pixelRowColToIndex(row, col);
+						// POLICY: PIXEL PRIOR
+						if (!p.pixelPrior(iVolumeIndex)) { x2L -= 1.0f; x2R -= 1.0f; continue; }
+						
+						// right
+						if (x2R >= V)		res = 1.0f;
+						else if (x2R > U)	res = x2R - (x2R-U)*(x2R-U)*inv_4T;
+						else if (x2R >= T)	res = x2R;
+						else if (x2R > S)	res = (x2R-S)*(x2R-S) * inv_4T;
+						else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+								
+						// left
+						if (x2L <= S)		{} // - 0.0f
+						else if (x2L < T)	res -= (x2L-S)*(x2L-S) * inv_4T;
+						else if (x2L <= U)	res -= x2L;
+						else if (x2L < V)	res -= x2L - (x2L-U)*(x2L-U)*inv_4T;
+						else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+						// POLICY: ADD
+						p.addWeight(iRayIndex, iVolumeIndex, PW*PH * res);
+
+						// POLICY: PIXEL POSTERIOR
+						p.pixelPosterior(iVolumeIndex);
+
+						x2L -= 1.0f;		
+						x2R -= 1.0f;
+
+					} // end col loop
+
+				} // end row loop
+
+				// POLICY: RAY POSTERIOR
+				p.rayPosterior(iRayIndex);
+
+			}	// end detector loop
+
+		// [45?,135?] and [225?,315?]
+		// horizontaly
+		} else {
+
+			// Precalculate kernel limits
+			S = -0.5f * fabs_cos_theta * fabs_inv_sin_theta;
+			T = -S;
+			U = 1.0f + S;
+			V = 1.0f - S;
+			inv_4T = 0.25f / T;
+
+			updateX = cos_theta * inv_sin_theta;
+
+			// loop detectors
+			for (iDetector = 0; iDetector < m_pProjectionGeometry->getDetectorCount(); ++iDetector) {
+			
+				iRayIndex = iAngle * m_pProjectionGeometry->getDetectorCount() + iDetector;
+
+				// POLICY: RAY PRIOR
+				if (!p.rayPrior(iRayIndex)) continue;
+
+				// get t
+				t = m_pProjectionGeometry->indexToDetectorOffset(iDetector);
+				if (switch_t) t = -t;
+			
+				// calculate left strip extremes (volume coordinates)
+				PL = (t - cos_theta * m_pVolumeGeometry->pixelColToCenterX(0) + DW*0.5f) * inv_sin_theta;
+				PLimitL = PL + 0.5f * fabs_cos_theta * fabs_inv_sin_theta * PW;
+				PLimitR = PLimitL - DW * inv_sin_theta - PH * fabs_cos_theta * fabs_inv_sin_theta; 
+
+				// calculate strip extremes (pixel coordinates)
+				XLimitL = (m_pVolumeGeometry->getWindowMaxY() - PLimitL) * inv_PH;
+				XLimitR = (m_pVolumeGeometry->getWindowMaxY() - PLimitR) * inv_PH;
+				xL = (m_pVolumeGeometry->getWindowMaxY() - PL) * inv_PH;
+				xR = xL + (DW * fabs_inv_sin_theta) * inv_PH;
+
+				// for each col
+				for (col = 0; col < m_pVolumeGeometry->getGridColCount(); ++col) {
+
+					// get strip extremes in column indices
+					x1L = int((XLimitL > 0.0f) ? XLimitL : XLimitL-1.0f);
+					x1R = int((XLimitR > 0.0f) ? XLimitR : XLimitR-1.0f);
+
+					// get coords w.r.t leftmost column hit by strip
+					x2L = xL - x1L; 
+					x2R = xR - x1L;
+					
+					// update strip extremes for the next row
+					XLimitL += updateX; 
+					XLimitR += updateX;
+					xL += updateX; 
+					xR += updateX; 
+
+					// for each affected col
+					for (row = x1L; row <= x1R; ++row) {
+
+						if (row < 0 || row >= m_pVolumeGeometry->getGridRowCount()) { x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+						iVolumeIndex = m_pVolumeGeometry->pixelRowColToIndex(row, col);
+
+						// POLICY: PIXEL PRIOR
+						if (!p.pixelPrior(iVolumeIndex)) { x2L -= 1.0f; x2R -= 1.0f; continue; }
+
+						// right
+						if (x2R >= V)		res = 1.0f;
+						else if (x2R > U)	res = x2R - (x2R-U)*(x2R-U)*inv_4T;
+						else if (x2R >= T)	res = x2R;
+						else if (x2R > S)	res = (x2R-S)*(x2R-S) * inv_4T;
+						else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+								
+						// left
+						if (x2L <= S)		{} // - 0.0f
+						else if (x2L < T)	res -= (x2L-S)*(x2L-S) * inv_4T;
+						else if (x2L <= U)	res -= x2L;
+						else if (x2L < V)	res -= x2L - (x2L-U)*(x2L-U)*inv_4T;
+						else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+						// POLICY: ADD
+						p.addWeight(iRayIndex, iVolumeIndex, PW*PH * res);
+
+						// POLICY: PIXEL POSTERIOR
+						p.pixelPosterior(iVolumeIndex);
+
+						x2L -= 1.0f;		
+						x2R -= 1.0f;
+
+					} // end row loop
+
+				} // end col loop
+
+				// POLICY: RAY POSTERIOR
+				p.rayPosterior(iRayIndex);
+
+			} // end detector loop
+
+
+		} // end theta switch
+
+	} // end angle loop
+}
+
+
+//----------------------------------------------------------------------------------------
+// PROJECT SINGLE PROJECTION
+template <typename Policy>
+void CParallelBeamStripKernelProjector2D::projectSingleProjection(int _iProjection, Policy& p)
+{
+	// Some variables
+	float32 theta, t;
+	int row, col, iDetector;
+	float32 res;
+	float32 PL, PLimitL, PLimitR;
+	float32 xL, xR, XLimitL, XLimitR;
+	int x1L,x1R;
+	float32 x2L, x2R, updateX;
+	int iVolumeIndex, iRayIndex;
+	
+	float32 sin_theta, cos_theta, inv_sin_theta, inv_cos_theta;
+	float32 fabs_sin_theta, fabs_cos_theta, fabs_inv_sin_theta, fabs_inv_cos_theta;
+	float32 PW, PH, DW, inv_PW, inv_PH;
+	float32 S, T, U, V, inv_4T;
+
+	// get values
+	theta = m_pProjectionGeometry->getProjectionAngle(_iProjection);
+	bool switch_t = false;
+	if (theta >= 7*PIdiv4) theta -= 2*PI;
+	if (theta >= 3*PIdiv4) {
+		theta -= PI;
+		switch_t = true;
+	}
+
+	// Precalculate sin, cos, 1/cos
+	sin_theta = sin(theta);
+	cos_theta = cos(theta);
+	inv_cos_theta = 1.0f / cos_theta; 
+	inv_sin_theta = 1.0f / sin_theta;
+
+	fabs_sin_theta = (sin_theta < 0.0f) ? -sin_theta : sin_theta;
+	fabs_cos_theta = (cos_theta < 0.0f) ? -cos_theta : cos_theta;
+	fabs_inv_cos_theta = (inv_cos_theta < 0.0f) ? -inv_cos_theta : inv_cos_theta;
+	fabs_inv_sin_theta = (inv_sin_theta < 0.0f) ? -inv_sin_theta : inv_sin_theta;
+
+	// Other precalculations
+	PW = m_pVolumeGeometry->getPixelLengthX();
+	PH = m_pVolumeGeometry->getPixelLengthY();
+	DW = m_pProjectionGeometry->getDetectorWidth();
+	inv_PW = 1.0f / PW;
+	inv_PH = 1.0f / PH;
+
+	// [-45?,45?] and [135?,225?]
+	if (theta < PIdiv4) {
+
+		// Precalculate kernel limits
+		S = -0.5f * fabs_sin_theta * fabs_inv_cos_theta;
+		T = -S;
+		U = 1.0f + S;
+		V = 1.0f - S;
+		inv_4T = 0.25f / T;
+
+		updateX = sin_theta * inv_cos_theta;
+
+		// loop detectors
+		for (iDetector = 0; iDetector < m_pProjectionGeometry->getDetectorCount(); ++iDetector) {
+		
+			iRayIndex = _iProjection * m_pProjectionGeometry->getDetectorCount() + iDetector;
+
+			// POLICY: RAY PRIOR
+			if (!p.rayPrior(iRayIndex)) continue;
+
+			// get t
+			t = m_pProjectionGeometry->indexToDetectorOffset(iDetector);
+			if (switch_t) t = -t;
+		
+			// calculate left strip extremes (volume coordinates)
+			PL = (t - sin_theta * m_pVolumeGeometry->pixelRowToCenterY(0) - DW*0.5f) * inv_cos_theta;
+			PLimitL = PL - 0.5f * fabs_sin_theta * fabs_inv_cos_theta * PH;
+			PLimitR = PLimitL + DW * inv_cos_theta + PH * fabs_sin_theta * fabs_inv_cos_theta; 
+
+			// calculate strip extremes (pixel coordinates)
+			XLimitL = (PLimitL - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+			XLimitR = (PLimitR - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+			xL = (PL - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+			xR = xL + (DW * inv_cos_theta) * inv_PW;
+
+			// for each row
+			for (row = 0; row < m_pVolumeGeometry->getGridRowCount(); ++row) {
+			
+				// get strip extremes in column indices
+				x1L = int((XLimitL > 0.0f) ? XLimitL : XLimitL-1.0f);
+				x1R = int((XLimitR > 0.0f) ? XLimitR : XLimitR-1.0f);
+
+				// get coords w.r.t leftmost column hit by strip
+				x2L = xL - x1L; 
+				x2R = xR - x1L;
+				
+				// update strip extremes for the next row
+				XLimitL += updateX; 
+				XLimitR += updateX;
+				xL += updateX; 
+				xR += updateX; 
+
+				// for each affected col
+				for (col = x1L; col <= x1R; ++col) {
+
+					if (col < 0 || col >= m_pVolumeGeometry->getGridColCount()) { x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+					iVolumeIndex = m_pVolumeGeometry->pixelRowColToIndex(row, col);
+
+					// POLICY: PIXEL PRIOR
+					if (!p.pixelPrior(iVolumeIndex)) { x2L -= 1.0f; x2R -= 1.0f; continue; }
+					
+					// right
+					if (x2R >= V)		res = 1.0f;
+					else if (x2R > U)	res = x2R - (x2R-U)*(x2R-U)*inv_4T;
+					else if (x2R >= T)	res = x2R;
+					else if (x2R > S)	res = (x2R-S)*(x2R-S) * inv_4T;
+					else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+							
+					// left
+					if (x2L <= S)		{} // - 0.0f
+					else if (x2L < T)	res -= (x2L-S)*(x2L-S) * inv_4T;
+					else if (x2L <= U)	res -= x2L;
+					else if (x2L < V)	res -= x2L - (x2L-U)*(x2L-U)*inv_4T;
+					else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+					// POLICY: ADD
+					p.addWeight(iRayIndex, iVolumeIndex, PW*PH * res);
+
+					// POLICY: PIXEL POSTERIOR
+					p.pixelPosterior(iVolumeIndex);
+
+					x2L -= 1.0f;		
+					x2R -= 1.0f;
+
+				} // end col loop
+
+			} // end row loop
+
+			// POLICY: RAY POSTERIOR
+			p.rayPosterior(iRayIndex);
+
+		}	// end detector loop
+
+	// [45?,135?] and [225?,315?]
+	// horizontaly
+	} else {
+
+		// Precalculate kernel limits
+		S = -0.5f * fabs_cos_theta * fabs_inv_sin_theta;
+		T = -S;
+		U = 1.0f + S;
+		V = 1.0f - S;
+		inv_4T = 0.25f / T;
+
+		updateX = cos_theta * inv_sin_theta;
+
+		// loop detectors
+		for (iDetector = 0; iDetector < m_pProjectionGeometry->getDetectorCount(); ++iDetector) {
+		
+			iRayIndex = _iProjection * m_pProjectionGeometry->getDetectorCount() + iDetector;
+
+			// POLICY: RAY PRIOR
+			if (!p.rayPrior(iRayIndex)) continue;
+
+			// get t
+			t = m_pProjectionGeometry->indexToDetectorOffset(iDetector);
+			if (switch_t) t = -t;
+		
+			// calculate left strip extremes (volume coordinates)
+			PL = (t - cos_theta * m_pVolumeGeometry->pixelColToCenterX(0) + DW*0.5f) * inv_sin_theta;
+			PLimitL = PL + 0.5f * fabs_cos_theta * fabs_inv_sin_theta * PW;
+			PLimitR = PLimitL - DW * inv_sin_theta - PH * fabs_cos_theta * fabs_inv_sin_theta; 
+
+			// calculate strip extremes (pixel coordinates)
+			XLimitL = (m_pVolumeGeometry->getWindowMaxY() - PLimitL) * inv_PH;
+			XLimitR = (m_pVolumeGeometry->getWindowMaxY() - PLimitR) * inv_PH;
+			xL = (m_pVolumeGeometry->getWindowMaxY() - PL) * inv_PH;
+			xR = xL + (DW * fabs_inv_sin_theta) * inv_PH;
+
+			// for each col
+			for (col = 0; col < m_pVolumeGeometry->getGridColCount(); ++col) {
+
+				// get strip extremes in column indices
+				x1L = int((XLimitL > 0.0f) ? XLimitL : XLimitL-1.0f);
+				x1R = int((XLimitR > 0.0f) ? XLimitR : XLimitR-1.0f);
+
+				// get coords w.r.t leftmost column hit by strip
+				x2L = xL - x1L; 
+				x2R = xR - x1L;
+				
+				// update strip extremes for the next row
+				XLimitL += updateX; 
+				XLimitR += updateX;
+				xL += updateX; 
+				xR += updateX; 
+
+				// for each affected col
+				for (row = x1L; row <= x1R; ++row) {
+
+					if (row < 0 || row >= m_pVolumeGeometry->getGridRowCount()) { x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+					iVolumeIndex = m_pVolumeGeometry->pixelRowColToIndex(row, col);
+
+					// POLICY: PIXEL PRIOR
+					if (!p.pixelPrior(iVolumeIndex)) { x2L -= 1.0f; x2R -= 1.0f; continue; }
+
+					// right
+					if (x2R >= V)		res = 1.0f;
+					else if (x2R > U)	res = x2R - (x2R-U)*(x2R-U)*inv_4T;
+					else if (x2R >= T)	res = x2R;
+					else if (x2R > S)	res = (x2R-S)*(x2R-S) * inv_4T;
+					else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+							
+					// left
+					if (x2L <= S)		{} // - 0.0f
+					else if (x2L < T)	res -= (x2L-S)*(x2L-S) * inv_4T;
+					else if (x2L <= U)	res -= x2L;
+					else if (x2L < V)	res -= x2L - (x2L-U)*(x2L-U)*inv_4T;
+					else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+					// POLICY: ADD
+					p.addWeight(iRayIndex, iVolumeIndex, PW*PH * res);
+
+					// POLICY: PIXEL POSTERIOR
+					p.pixelPosterior(iVolumeIndex);
+
+					x2L -= 1.0f;		
+					x2R -= 1.0f;
+
+				} // end row loop
+
+			} // end col loop
+
+			// POLICY: RAY POSTERIOR
+			p.rayPosterior(iRayIndex);
+
+		} // end detector loop
+
+	} // end theta switch
+}
+
+
+//----------------------------------------------------------------------------------------
+// PROJECT SINGLE RAY
+template <typename Policy>
+void CParallelBeamStripKernelProjector2D::projectSingleRay(int _iProjection, int _iDetector, Policy& p)
+{
+	int iRayIndex = _iProjection * m_pProjectionGeometry->getDetectorCount() + _iDetector;
+
+	// POLICY: RAY PRIOR
+	if (!p.rayPrior(iRayIndex)) return;
+
+	// Some variables
+	float32 theta, t;
+	int row, col;
+	float32 res;
+	float32 PL, PLimitL, PLimitR;
+	float32 xL, xR, XLimitL, XLimitR;
+	int x1L,x1R;
+	float32 x2L, x2R, updateX;
+	int iVolumeIndex;
+	
+	float32 sin_theta, cos_theta, inv_sin_theta, inv_cos_theta;
+	float32 fabs_sin_theta, fabs_cos_theta, fabs_inv_sin_theta, fabs_inv_cos_theta;
+	float32 PW, PH, DW, inv_PW, inv_PH;
+	float32 S, T, U, V, inv_4T;
+
+	// get values
+	theta = m_pProjectionGeometry->getProjectionAngle(_iProjection);
+	bool switch_t = false;
+	if (theta >= 7*PIdiv4) theta -= 2*PI;
+	if (theta >= 3*PIdiv4) {
+		theta -= PI;
+		switch_t = true;
+	}
+
+	// Precalculate sin, cos, 1/cos
+	sin_theta = sin(theta);
+	cos_theta = cos(theta);
+	inv_cos_theta = 1.0f / cos_theta; 
+	inv_sin_theta = 1.0f / sin_theta;
+
+	fabs_sin_theta = (sin_theta < 0.0f) ? -sin_theta : sin_theta;
+	fabs_cos_theta = (cos_theta < 0.0f) ? -cos_theta : cos_theta;
+	fabs_inv_cos_theta = (inv_cos_theta < 0.0f) ? -inv_cos_theta : inv_cos_theta;
+	fabs_inv_sin_theta = (inv_sin_theta < 0.0f) ? -inv_sin_theta : inv_sin_theta;
+
+	// Other precalculations
+	PW = m_pVolumeGeometry->getPixelLengthX();
+	PH = m_pVolumeGeometry->getPixelLengthY();
+	DW = m_pProjectionGeometry->getDetectorWidth();
+	inv_PW = 1.0f / PW;
+	inv_PH = 1.0f / PH;
+
+	// [-45?,45?] and [135?,225?]
+	if (theta < PIdiv4) {
+
+		// Precalculate kernel limits
+		S = -0.5f * fabs_sin_theta * fabs_inv_cos_theta;
+		T = -S;
+		U = 1.0f + S;
+		V = 1.0f - S;
+		inv_4T = 0.25f / T;
+
+		updateX = sin_theta * inv_cos_theta;
+		
+		// get t
+		t = m_pProjectionGeometry->indexToDetectorOffset(_iDetector);
+		if (switch_t) t = -t;
+	
+		// calculate left strip extremes (volume coordinates)
+		PL = (t - sin_theta * m_pVolumeGeometry->pixelRowToCenterY(0) - DW*0.5f) * inv_cos_theta;
+		PLimitL = PL - 0.5f * fabs_sin_theta * fabs_inv_cos_theta * PH;
+		PLimitR = PLimitL + DW * inv_cos_theta + PH * fabs_sin_theta * fabs_inv_cos_theta; 
+
+		// calculate strip extremes (pixel coordinates)
+		XLimitL = (PLimitL - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+		XLimitR = (PLimitR - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+		xL = (PL - m_pVolumeGeometry->getWindowMinX()) * inv_PW;
+		xR = xL + (DW * inv_cos_theta) * inv_PW;
+
+		// for each row
+		for (row = 0; row < m_pVolumeGeometry->getGridRowCount(); ++row) {
+		
+			// get strip extremes in column indices
+			x1L = int((XLimitL > 0.0f) ? XLimitL : XLimitL-1.0f);
+			x1R = int((XLimitR > 0.0f) ? XLimitR : XLimitR-1.0f);
+
+			// get coords w.r.t leftmost column hit by strip
+			x2L = xL - x1L; 
+			x2R = xR - x1L;
+			
+			// update strip extremes for the next row
+			XLimitL += updateX; 
+			XLimitR += updateX;
+			xL += updateX; 
+			xR += updateX; 
+
+			// for each affected col
+			for (col = x1L; col <= x1R; ++col) {
+
+				if (col < 0 || col >= m_pVolumeGeometry->getGridColCount()) { x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+				iVolumeIndex = m_pVolumeGeometry->pixelRowColToIndex(row, col);
+
+				// POLICY: PIXEL PRIOR
+				if (!p.pixelPrior(iVolumeIndex)) { x2L -= 1.0f; x2R -= 1.0f; continue; }
+				
+				// right
+				if (x2R >= V)		res = 1.0f;
+				else if (x2R > U)	res = x2R - (x2R-U)*(x2R-U)*inv_4T;
+				else if (x2R >= T)	res = x2R;
+				else if (x2R > S)	res = (x2R-S)*(x2R-S) * inv_4T;
+				else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+						
+				// left
+				if (x2L <= S)		{} // - 0.0f
+				else if (x2L < T)	res -= (x2L-S)*(x2L-S) * inv_4T;
+				else if (x2L <= U)	res -= x2L;
+				else if (x2L < V)	res -= x2L - (x2L-U)*(x2L-U)*inv_4T;
+				else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+				// POLICY: ADD
+				p.addWeight(iRayIndex, iVolumeIndex, PW*PH * res);
+
+				// POLICY: PIXEL POSTERIOR
+				p.pixelPosterior(iVolumeIndex);
+
+				x2L -= 1.0f;		
+				x2R -= 1.0f;
+
+			} // end col loop
+
+		} // end row loop
+
+	// [45?,135?] and [225?,315?]
+	// horizontaly
+	} else {
+
+		// Precalculate kernel limits
+		S = -0.5f * fabs_cos_theta * fabs_inv_sin_theta;
+		T = -S;
+		U = 1.0f + S;
+		V = 1.0f - S;
+		inv_4T = 0.25f / T;
+
+		updateX = cos_theta * inv_sin_theta;
+
+		// get t
+		t = m_pProjectionGeometry->indexToDetectorOffset(_iDetector);
+		if (switch_t) t = -t;
+	
+		// calculate left strip extremes (volume coordinates)
+		PL = (t - cos_theta * m_pVolumeGeometry->pixelColToCenterX(0) + DW*0.5f) * inv_sin_theta;
+		PLimitL = PL + 0.5f * fabs_cos_theta * fabs_inv_sin_theta * PW;
+		PLimitR = PLimitL - DW * inv_sin_theta - PH * fabs_cos_theta * fabs_inv_sin_theta; 
+
+		// calculate strip extremes (pixel coordinates)
+		XLimitL = (m_pVolumeGeometry->getWindowMaxY() - PLimitL) * inv_PH;
+		XLimitR = (m_pVolumeGeometry->getWindowMaxY() - PLimitR) * inv_PH;
+		xL = (m_pVolumeGeometry->getWindowMaxY() - PL) * inv_PH;
+		xR = xL + (DW * fabs_inv_sin_theta) * inv_PH;
+
+		// for each col
+		for (col = 0; col < m_pVolumeGeometry->getGridColCount(); ++col) {
+
+			// get strip extremes in column indices
+			x1L = int((XLimitL > 0.0f) ? XLimitL : XLimitL-1.0f);
+			x1R = int((XLimitR > 0.0f) ? XLimitR : XLimitR-1.0f);
+
+			// get coords w.r.t leftmost column hit by strip
+			x2L = xL - x1L; 
+			x2R = xR - x1L;
+			
+			// update strip extremes for the next row
+			XLimitL += updateX; 
+			XLimitR += updateX;
+			xL += updateX; 
+			xR += updateX; 
+
+			// for each affected col
+			for (row = x1L; row <= x1R; ++row) {
+
+				if (row < 0 || row >= m_pVolumeGeometry->getGridRowCount()) { x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+				iVolumeIndex = m_pVolumeGeometry->pixelRowColToIndex(row, col);
+
+				// POLICY: PIXEL PRIOR
+				if (!p.pixelPrior(iVolumeIndex)) { x2L -= 1.0f; x2R -= 1.0f; continue; }
+
+				// right
+				if (x2R >= V)		res = 1.0f;
+				else if (x2R > U)	res = x2R - (x2R-U)*(x2R-U)*inv_4T;
+				else if (x2R >= T)	res = x2R;
+				else if (x2R > S)	res = (x2R-S)*(x2R-S) * inv_4T;
+				else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+						
+				// left
+				if (x2L <= S)		{} // - 0.0f
+				else if (x2L < T)	res -= (x2L-S)*(x2L-S) * inv_4T;
+				else if (x2L <= U)	res -= x2L;
+				else if (x2L < V)	res -= x2L - (x2L-U)*(x2L-U)*inv_4T;
+				else				{ x2L -= 1.0f; x2R -= 1.0f;	continue; }
+
+				// POLICY: ADD
+				p.addWeight(iRayIndex, iVolumeIndex, PW*PH * res);
+
+				// POLICY: PIXEL POSTERIOR
+				p.pixelPosterior(iVolumeIndex);
+
+				x2L -= 1.0f;		
+				x2R -= 1.0f;
+
+			} // end row loop
+
+		} // end col loop
+
+	} // end theta switch
+
+	// POLICY: RAY POSTERIOR
+	p.rayPosterior(iRayIndex);
+
+}