Add basic implementation of par2d CPU Distance Driven projector

7 files changed, 615 insertions, 2 deletions

diff --git a/build/linux/Makefile.in b/build/linux/Makefile.in
index 7c4089a..078a1a2 100644
--- a/build/linux/Makefile.in
+++ b/build/linux/Makefile.in
@@ -168,6 +168,7 @@ BASE_OBJECTS=\
 	src/Globals.lo \
 	src/Logging.lo \
 	src/ParallelBeamBlobKernelProjector2D.lo \
+	src/ParallelBeamDistanceDrivenProjector2D.lo \
 	src/ParallelBeamLinearKernelProjector2D.lo \
 	src/ParallelBeamLineKernelProjector2D.lo \
 	src/ParallelBeamStripKernelProjector2D.lo \
diff --git a/build/msvc/gen.py b/build/msvc/gen.py
index 42d0e0e..2200ecc 100644
--- a/build/msvc/gen.py
+++ b/build/msvc/gen.py
@@ -249,6 +249,7 @@ P_astra["filters"]["Projectors\\source"] = [
 "src\\FanFlatBeamLineKernelProjector2D.cpp",
 "src\\FanFlatBeamStripKernelProjector2D.cpp",
 "src\\ParallelBeamBlobKernelProjector2D.cpp",
+"src\\ParallelBeamDistanceDrivenProjector2D.cpp",
 "src\\ParallelBeamLinearKernelProjector2D.cpp",
 "src\\ParallelBeamLineKernelProjector2D.cpp",
 "src\\ParallelBeamStripKernelProjector2D.cpp",
@@ -393,6 +394,7 @@ P_astra["filters"]["Projectors\\headers"] = [
 "include\\astra\\FanFlatBeamLineKernelProjector2D.h",
 "include\\astra\\FanFlatBeamStripKernelProjector2D.h",
 "include\\astra\\ParallelBeamBlobKernelProjector2D.h",
+"include\\astra\\ParallelBeamDistanceDrivenProjector2D.h",
 "include\\astra\\ParallelBeamLinearKernelProjector2D.h",
 "include\\astra\\ParallelBeamLineKernelProjector2D.h",
 "include\\astra\\ParallelBeamStripKernelProjector2D.h",
diff --git a/include/astra/ParallelBeamDistanceDrivenProjector2D.h b/include/astra/ParallelBeamDistanceDrivenProjector2D.h
new file mode 100644
index 0000000..67dd21b
--- /dev/null
+++ b/include/astra/ParallelBeamDistanceDrivenProjector2D.h
@@ -0,0 +1,205 @@
+/*
+-----------------------------------------------------------------------
+Copyright: 2010-2018, imec Vision Lab, University of Antwerp
+           2014-2018, CWI, Amsterdam
+
+Contact: astra@astra-toolbox.com
+Website: http://www.astra-toolbox.com/
+
+This file is part of the 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/>.
+
+-----------------------------------------------------------------------
+*/
+
+#ifndef _INC_ASTRA_PARALLELDISTANCEDRIVENPROJECTOR
+#define _INC_ASTRA_PARALLELDISTANCEDRIVENPROJECTOR
+
+#include "ParallelProjectionGeometry2D.h"
+#include "ParallelVecProjectionGeometry2D.h"
+#include "Float32Data2D.h"
+#include "Projector2D.h"
+
+#include "Float32ProjectionData2D.h"
+#include "Float32VolumeData2D.h"
+
+namespace astra
+{
+
+/** This class implements a "distance driven" two-dimensional projector.
+ *
+ * Reference:
+ * De Man, Bruno, and Samit Basu. “Distance-Driven Projection and Backprojection in Three Dimensions.” Physics in Medicine and Biology 49, no. 11 (2004): 2463.
+ *
+ * \par XML Configuration
+ * \astra_xml_item{ProjectionGeometry, xml node, The geometry of the projection.}
+ * \astra_xml_item{VolumeGeometry, xml node, The geometry of the volume.}
+ *
+ * \par MATLAB example
+ * \astra_code{
+ *		cfg = astra_struct('distance_driven');\n
+ *		cfg.ProjectionGeometry = proj_geom;\n
+ *		cfg.VolumeGeometry = vol_geom;\n
+ *		proj_id = astra_mex_projector('create'\, cfg);\n
+ * }
+ */
+class _AstraExport CParallelBeamDistanceDrivenProjector2D : public CProjector2D {
+
+protected:
+	
+	/** Initial clearing. Only to be used by constructors.
+	 */
+	virtual void _clear();
+
+	/** Check the values of this object.  If everything is ok, the object can be set to the initialized state.
+	 * The following statements are then guaranteed to hold:
+	 * - no NULL pointers
+	 * - all sub-objects are initialized properly
+	 * - blobvalues are ok
+	 */
+	virtual bool _check();
+
+public:
+
+	// type of the projector, needed to register with CProjectorFactory
+	static std::string type;
+
+	/** Default constructor.
+	 */
+	CParallelBeamDistanceDrivenProjector2D();
+
+	/** Constructor.
+	 * 
+	 * @param _pProjectionGeometry		Information class about the geometry of the projection.  Will be HARDCOPIED.
+	 * @param _pReconstructionGeometry	Information class about the geometry of the reconstruction volume. Will be HARDCOPIED.
+	 */
+	CParallelBeamDistanceDrivenProjector2D(CParallelProjectionGeometry2D* _pProjectionGeometry, 
+										 CVolumeGeometry2D* _pReconstructionGeometry);
+	
+	/** Destructor, is virtual to show that we are aware subclass destructor are called.
+	 */	
+	~CParallelBeamDistanceDrivenProjector2D();
+
+	/** Initialize the projector with a config object.
+	 *
+	 * @param _cfg Configuration Object
+	 * @return initialization successful?
+	 */
+	virtual bool initialize(const Config& _cfg);
+
+	/** Initialize the projector.
+	 *
+	 * @param _pProjectionGeometry		Information class about the geometry of the projection.  Will be HARDCOPIED.
+	 * @param _pReconstructionGeometry	Information class about the geometry of the reconstruction volume.  Will be HARDCOPIED.
+	 * @return initialization successful?
+	 */
+	virtual bool initialize(CParallelProjectionGeometry2D* _pProjectionGeometry, 
+							CVolumeGeometry2D* _pVolumeGeometry);
+
+	/** Clear this class.
+	 */
+	virtual void clear();
+
+	/** Returns the number of weights required for storage of all weights of one projection.
+	 *
+	 * @param _iProjectionIndex Index of the projection (zero-based).
+	 * @return Size of buffer (given in SPixelWeight elements) needed to store weighted pixels.
+	 */
+	virtual int getProjectionWeightsCount(int _iProjectionIndex);
+
+	/** Compute the pixel weights for a single ray, from the source to a detector pixel. 
+	 *
+	 * @param _iProjectionIndex	Index of the projection 
+	 * @param _iDetectorIndex	Index of the detector pixel
+	 * @param _pWeightedPixels	Pointer to a pre-allocated array, consisting of _iMaxPixelCount elements
+	 *							of type SPixelWeight. On return, this array contains a list of the index
+	 *							and weight for all pixels on the ray.
+	 * @param _iMaxPixelCount	Maximum number of pixels (and corresponding weights) that can be stored in _pWeightedPixels.
+	 *							This number MUST be greater than the total number of pixels on the ray.
+	 * @param _iStoredPixelCount On return, this variable contains the total number of pixels on the 
+	 *                           ray (that have been stored in the list _pWeightedPixels). 
+     */
+	virtual void computeSingleRayWeights(int _iProjectionIndex, 
+										 int _iDetectorIndex, 
+										 SPixelWeight* _pWeightedPixels,
+		                                 int _iMaxPixelCount, 
+										 int& _iStoredPixelCount);
+	
+	/** Create a list of detectors that are influenced by point [_iRow, _iCol].
+	 *
+	 * @param _iRow row of the point
+	 * @param _iCol column of the point
+	 * @return list of SDetector2D structs
+	 */
+	virtual std::vector<SDetector2D> projectPoint(int _iRow, int _iCol);
+
+
+	/** Policy-based projection of all rays.  This function will calculate each non-zero projection 
+	 * weight and use this value for a task provided by the policy object.
+	 *
+	 * @param _policy Policy object.  Should contain prior, addWeight and posterior function.
+	 */
+	template <typename Policy>
+	void project(Policy& _policy);
+
+	/** Policy-based projection of all rays of a single projection.  This function will calculate 
+	 * each non-zero projection weight and use this value for a task provided by the policy object.
+	 *
+	 * @param _iProjection Which projection should be projected?
+	 * @param _policy Policy object.  Should contain prior, addWeight and posterior function.
+	 */
+	template <typename Policy>
+	void projectSingleProjection(int _iProjection, Policy& _policy);
+
+	/** Policy-based projection of a single ray.  This function will calculate each non-zero 
+	 * projection  weight and use this value for a task provided by the policy object.
+	 *
+	 * @param _iProjection Which projection should be projected?
+	 * @param _iDetector Which detector should be projected?
+	 * @param _policy Policy object.  Should contain prior, addWeight and posterior function.
+	 */
+	template <typename Policy>
+	void projectSingleRay(int _iProjection, int _iDetector, Policy& _policy);
+
+	/** Return the  type of this projector.
+	 *
+	 * @return identification type of this projector
+	 */
+	virtual std::string getType();
+
+
+protected:
+	/** Internal policy-based projection of a range of angles and range.
+ 	 * (_i*From is inclusive, _i*To exclusive) */
+	template <typename Policy>
+	void projectBlock_internal(int _iProjFrom, int _iProjTo,
+	                           int _iDetFrom, int _iDetTo, Policy& _policy);
+
+};
+
+//----------------------------------------------------------------------------------------
+
+inline std::string CParallelBeamDistanceDrivenProjector2D::getType() 
+{ 
+	return type; 
+}
+
+
+} // namespace astra
+
+
+#endif 
+
diff --git a/include/astra/ParallelBeamDistanceDrivenProjector2D.inl b/include/astra/ParallelBeamDistanceDrivenProjector2D.inl
new file mode 100644
index 0000000..6bf3b56
--- /dev/null
+++ b/include/astra/ParallelBeamDistanceDrivenProjector2D.inl
@@ -0,0 +1,227 @@
+/*
+-----------------------------------------------------------------------
+Copyright: 2010-2018, imec Vision Lab, University of Antwerp
+           2014-2018, CWI, Amsterdam
+
+Contact: astra@astra-toolbox.com
+Website: http://www.astra-toolbox.com/
+
+This file is part of the 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/>.
+
+-----------------------------------------------------------------------
+*/
+
+#define policy_weight(p,rayindex,volindex,weight) do { if (p.pixelPrior(volindex)) { p.addWeight(rayindex, volindex, weight); p.pixelPosterior(volindex); } } while (false)
+
+template <typename Policy>
+void CParallelBeamDistanceDrivenProjector2D::project(Policy& p)
+{
+	projectBlock_internal(0, m_pProjectionGeometry->getProjectionAngleCount(),
+		                  0, m_pProjectionGeometry->getDetectorCount(), p);
+}
+
+template <typename Policy>
+void CParallelBeamDistanceDrivenProjector2D::projectSingleProjection(int _iProjection, Policy& p)
+{
+	projectBlock_internal(_iProjection, _iProjection + 1,
+	                      0, m_pProjectionGeometry->getDetectorCount(), p);
+}
+
+template <typename Policy>
+void CParallelBeamDistanceDrivenProjector2D::projectSingleRay(int _iProjection, int _iDetector, Policy& p)
+{
+	projectBlock_internal(_iProjection, _iProjection + 1,
+	                      _iDetector, _iDetector + 1, p);
+}
+
+
+
+
+
+template <typename Policy>
+void CParallelBeamDistanceDrivenProjector2D::projectBlock_internal(int _iProjFrom, int _iProjTo, int _iDetFrom, int _iDetTo, Policy& p)
+{
+	// get vector geometry
+	const CParallelVecProjectionGeometry2D* pVecProjectionGeometry;
+	if (dynamic_cast<CParallelProjectionGeometry2D*>(m_pProjectionGeometry)) {
+		pVecProjectionGeometry = dynamic_cast<CParallelProjectionGeometry2D*>(m_pProjectionGeometry)->toVectorGeometry();
+	} else {
+		pVecProjectionGeometry = dynamic_cast<CParallelVecProjectionGeometry2D*>(m_pProjectionGeometry);
+	}
+
+	// precomputations
+	const float32 pixelLengthX = m_pVolumeGeometry->getPixelLengthX();
+	const float32 pixelLengthY = m_pVolumeGeometry->getPixelLengthY();
+	const float32 inv_pixelLengthX = 1.0f / pixelLengthX;
+	const float32 inv_pixelLengthY = 1.0f / pixelLengthY;
+	const int colCount = m_pVolumeGeometry->getGridColCount();
+	const int rowCount = m_pVolumeGeometry->getGridRowCount();
+
+	// Performance note:
+	// This is not a very well optimizated version of the distance driven
+	// projector. The CPU projector model in ASTRA requires ray-driven iteration,
+	// which limits re-use of intermediate computations.
+
+	// loop angles
+	for (int iAngle = _iProjFrom; iAngle < _iProjTo; ++iAngle) {
+
+		const SParProjection * proj = &pVecProjectionGeometry->getProjectionVectors()[iAngle];
+
+		float32 detSize = sqrt(proj->fDetUX * proj->fDetUX + proj->fDetUY * proj->fDetUY);
+
+		const bool vertical = fabs(proj->fRayX) < fabs(proj->fRayY);
+
+		const float32 Ex = m_pVolumeGeometry->getWindowMinX() + pixelLengthX*0.5f;
+		const float32 Ey = m_pVolumeGeometry->getWindowMaxY() - pixelLengthY*0.5f;
+
+		// loop detectors
+		for (int iDetector = _iDetFrom; iDetector < _iDetTo; ++iDetector) {
+
+			const int iRayIndex = iAngle * m_pProjectionGeometry->getDetectorCount() + iDetector;
+
+			// POLICY: RAY PRIOR
+			if (!p.rayPrior(iRayIndex)) continue;
+
+			const float32 Dx = proj->fDetSX + (iDetector+0.5f) * proj->fDetUX;
+			const float32 Dy = proj->fDetSY + (iDetector+0.5f) * proj->fDetUY;
+
+			if (vertical && true) {
+
+				const float32 RxOverRy = proj->fRayX/proj->fRayY;
+				// TODO: Determine det/pixel scaling factors
+				const float32 lengthPerRow = m_pVolumeGeometry->getPixelLengthX() * m_pVolumeGeometry->getPixelLengthY();
+				const float32 deltac = -pixelLengthY * RxOverRy * inv_pixelLengthX;
+				const float32 deltad = fabs((proj->fDetUX - proj->fDetUY * RxOverRy) * inv_pixelLengthX);
+
+				// calculate c for row 0
+				float32 c = (Dx + (Ey - Dy)*RxOverRy - Ex) * inv_pixelLengthX + 0.5f;
+
+				// loop rows
+				for (int row = 0; row < rowCount; ++row, c+= deltac) {
+
+					// horizontal extent of ray in center of this row:
+					// [ c - deltad/2 , c + deltad/2 ]
+
+					// |-gapBegin-*---|------|----*-gapEnd-|
+					// * = ray extent intercepts; c - deltad/2 and c + deltad/2
+					// | = pixel column edges
+
+					const int colBegin = (int)floor(c - deltad/2.0f);
+					const int colEnd = (int)ceil(c + deltad/2.0f);
+
+					// TODO: Optimize volume edge checks
+
+					int iVolumeIndex = row * colCount + colBegin;
+					if (colBegin + 1 == colEnd) {
+
+						if (colBegin >= 0 && colBegin < colCount)
+							policy_weight(p, iRayIndex, iVolumeIndex,
+							              deltad * lengthPerRow);
+					} else {
+						const float gapBegin = (c - deltad/2.0f) - (float32)colBegin;
+						const float gapEnd = (float32)colEnd - (c + deltad/2.0f);
+						float tot = 1.0f - gapBegin;
+						if (colBegin >= 0 && colBegin < colCount) {
+							policy_weight(p, iRayIndex, iVolumeIndex,
+							              (1.0f - gapBegin) * lengthPerRow);
+						}
+						iVolumeIndex++;
+
+						for (int col = colBegin + 1; col + 1 < colEnd; ++col, ++iVolumeIndex) {
+							tot += 1.0f;
+							if (col >= 0 && col < colCount) {
+								policy_weight(p, iRayIndex, iVolumeIndex, lengthPerRow);
+							}
+						}
+						assert(iVolumeIndex == row * colCount + colEnd - 1);
+						tot += 1.0f - gapEnd;
+						if (colEnd > 0 && colEnd <= colCount) {
+							policy_weight(p, iRayIndex, iVolumeIndex,
+						 	             (1.0f - gapEnd) * lengthPerRow);
+						}
+						assert(fabs(tot - deltad) < 0.0001);
+					}
+
+				}
+				
+			} else if (!vertical && true) {
+
+				const float32 RyOverRx = proj->fRayY/proj->fRayX;
+				// TODO: Determine det/pixel scaling factors
+				const float32 lengthPerCol = m_pVolumeGeometry->getPixelLengthX() * m_pVolumeGeometry->getPixelLengthY();
+				const float32 deltar = -pixelLengthX * RyOverRx * inv_pixelLengthY;
+				const float32 deltad = fabs((proj->fDetUY - proj->fDetUX * RyOverRx) * inv_pixelLengthY);
+
+				// calculate r for col 0
+				float32 r = -(Dy + (Ex - Dx)*RyOverRx - Ey) * inv_pixelLengthY + 0.5f;
+
+				// loop columns
+				for (int col = 0; col < colCount; ++col, r+= deltar) {
+
+					// vertical extent of ray in center of this column:
+					// [ r - deltad/2 , r + deltad/2 ]
+
+					const int rowBegin = (int)floor(r - deltad/2.0f);
+					const int rowEnd = (int)ceil(r + deltad/2.0f);
+
+					// TODO: Optimize volume edge checks
+
+					int iVolumeIndex = rowBegin * colCount + col;
+					if (rowBegin + 1 == rowEnd) {
+
+						if (rowBegin >= 0 && rowBegin < rowCount)
+							policy_weight(p, iRayIndex, iVolumeIndex,
+							              deltad * lengthPerCol);
+					} else {
+						const float gapBegin = (r - deltad/2.0f) - (float32)rowBegin;
+						const float gapEnd = (float32)rowEnd - (r + deltad/2.0f);
+						float tot = 1.0f - gapBegin;
+
+						if (rowBegin >= 0 && rowBegin < rowCount) {
+							policy_weight(p, iRayIndex, iVolumeIndex,
+							              (1.0f - gapBegin) * lengthPerCol);
+						}
+						iVolumeIndex += colCount;
+
+						for (int row = rowBegin + 1; row + 1 < rowEnd; ++row, iVolumeIndex += colCount) {
+							tot += 1.0f;
+							if (row >= 0 && row < rowCount) {
+								policy_weight(p, iRayIndex, iVolumeIndex, lengthPerCol);
+							}
+						}
+						assert(iVolumeIndex == (rowEnd - 1) * colCount + col);
+						tot += 1.0f - gapEnd;
+						if (rowEnd > 0 && rowEnd <= rowCount) {
+							policy_weight(p, iRayIndex, iVolumeIndex,
+						 	             (1.0f - gapEnd) * lengthPerCol);
+						}
+						assert(fabs(tot - deltad) < 0.0001);
+					}
+
+				}
+
+			}
+
+			// POLICY: RAY POSTERIOR
+			p.rayPosterior(iRayIndex);
+	
+		}
+	}
+
+	if (dynamic_cast<CParallelProjectionGeometry2D*>(m_pProjectionGeometry))
+		delete pVecProjectionGeometry;
+}
diff --git a/include/astra/Projector2DImpl.inl b/include/astra/Projector2DImpl.inl
index b7edb1f..1308141 100644
--- a/include/astra/Projector2DImpl.inl
+++ b/include/astra/Projector2DImpl.inl
@@ -26,6 +26,7 @@ along with the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
 */
 
 
+#include "ParallelBeamDistanceDrivenProjector2D.inl"
 #include "ParallelBeamLinearKernelProjector2D.inl"
 #include "ParallelBeamLineKernelProjector2D.inl"
 #include "ParallelBeamStripKernelProjector2D.inl"
diff --git a/include/astra/ProjectorTypelist.h b/include/astra/ProjectorTypelist.h
index 1a65aad..063693d 100644
--- a/include/astra/ProjectorTypelist.h
+++ b/include/astra/ProjectorTypelist.h
@@ -35,6 +35,7 @@ along with the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
 #include "Projector2D.h"
 #include "ParallelBeamLineKernelProjector2D.h"
 #include "ParallelBeamLinearKernelProjector2D.h"
+#include "ParallelBeamDistanceDrivenProjector2D.h"
 #include "ParallelBeamBlobKernelProjector2D.h"
 #include "ParallelBeamStripKernelProjector2D.h"
 #include "SparseMatrixProjector2D.h"
@@ -46,9 +47,10 @@ namespace astra{
 
 #ifdef ASTRA_CUDA
 
-	typedef TYPELIST_8(
+	typedef TYPELIST_9(
 				CFanFlatBeamLineKernelProjector2D,
 				CFanFlatBeamStripKernelProjector2D,
+				CParallelBeamDistanceDrivenProjector2D,
 				CParallelBeamLinearKernelProjector2D,
 				CParallelBeamLineKernelProjector2D,
 				CParallelBeamBlobKernelProjector2D,
@@ -59,9 +61,10 @@ namespace astra{
 
 #else
 
-	typedef TYPELIST_7(
+	typedef TYPELIST_8(
 				CFanFlatBeamLineKernelProjector2D,
 				CFanFlatBeamStripKernelProjector2D,
+				CParallelBeamDistanceDrivenProjector2D,
 				CParallelBeamLinearKernelProjector2D,
 				CParallelBeamLineKernelProjector2D,
 				CParallelBeamBlobKernelProjector2D,
diff --git a/src/ParallelBeamDistanceDrivenProjector2D.cpp b/src/ParallelBeamDistanceDrivenProjector2D.cpp
new file mode 100644
index 0000000..a4ac450
--- /dev/null
+++ b/src/ParallelBeamDistanceDrivenProjector2D.cpp
@@ -0,0 +1,174 @@
+/*
+-----------------------------------------------------------------------
+Copyright: 2010-2018, imec Vision Lab, University of Antwerp
+           2014-2018, CWI, Amsterdam
+
+Contact: astra@astra-toolbox.com
+Website: http://www.astra-toolbox.com/
+
+This file is part of the 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/>.
+
+-----------------------------------------------------------------------
+*/
+
+#include "astra/ParallelBeamDistanceDrivenProjector2D.h"
+
+#include <cmath>
+#include <algorithm>
+
+#include "astra/DataProjectorPolicies.h"
+
+using namespace std;
+using namespace astra;
+
+#include "astra/ParallelBeamDistanceDrivenProjector2D.inl"
+
+// type of the projector, needed to register with CProjectorFactory
+std::string CParallelBeamDistanceDrivenProjector2D::type = "distance_driven";
+
+//----------------------------------------------------------------------------------------
+// default constructor
+CParallelBeamDistanceDrivenProjector2D::CParallelBeamDistanceDrivenProjector2D()
+{
+	_clear();
+}
+
+
+//----------------------------------------------------------------------------------------
+// constructor
+CParallelBeamDistanceDrivenProjector2D::CParallelBeamDistanceDrivenProjector2D(CParallelProjectionGeometry2D* _pProjectionGeometry,
+																		   CVolumeGeometry2D* _pReconstructionGeometry)
+
+{
+	_clear();
+	initialize(_pProjectionGeometry, _pReconstructionGeometry);
+}
+
+//----------------------------------------------------------------------------------------
+// destructor
+CParallelBeamDistanceDrivenProjector2D::~CParallelBeamDistanceDrivenProjector2D()
+{
+	clear();
+}
+
+//---------------------------------------------------------------------------------------
+// Clear - CParallelBeamDistanceDrivenProjector2D
+void CParallelBeamDistanceDrivenProjector2D::_clear()
+{
+	CProjector2D::_clear();
+	m_bIsInitialized = false;
+}
+
+//---------------------------------------------------------------------------------------
+// Clear - Public
+void CParallelBeamDistanceDrivenProjector2D::clear()
+{
+	CProjector2D::clear();
+	m_bIsInitialized = false;
+}
+
+//---------------------------------------------------------------------------------------
+// Check
+bool CParallelBeamDistanceDrivenProjector2D::_check()
+{
+	// check base class
+	ASTRA_CONFIG_CHECK(CProjector2D::_check(), "ParallelBeamDistanceDrivenProjector2D", "Error in Projector2D initialization");
+
+	ASTRA_CONFIG_CHECK(dynamic_cast<CParallelProjectionGeometry2D*>(m_pProjectionGeometry) || dynamic_cast<CParallelVecProjectionGeometry2D*>(m_pProjectionGeometry), "ParallelBeamDistanceDrivenProjector2D", "Unsupported projection geometry");
+
+	ASTRA_CONFIG_CHECK(abs(m_pVolumeGeometry->getPixelLengthX() / m_pVolumeGeometry->getPixelLengthY()) - 1 < eps, "ParallelBeamDistanceDrivenProjector2D", "Pixel height must equal pixel width.");
+
+	// success
+	return true;
+}
+
+//---------------------------------------------------------------------------------------
+// Initialize, use a Config object
+bool CParallelBeamDistanceDrivenProjector2D::initialize(const Config& _cfg)
+{
+	ASTRA_ASSERT(_cfg.self);
+
+	// if already initialized, clear first
+	if (m_bIsInitialized) {
+		clear();
+	}
+
+	// initialization of parent class
+	if (!CProjector2D::initialize(_cfg)) {
+		return false;
+	}
+
+	// success
+	m_bIsInitialized = _check();
+	return m_bIsInitialized;
+}
+
+//---------------------------------------------------------------------------------------
+// Initialize
+bool CParallelBeamDistanceDrivenProjector2D::initialize(CParallelProjectionGeometry2D* _pProjectionGeometry, 
+                                                        CVolumeGeometry2D* _pVolumeGeometry)
+{
+	// if already initialized, clear first
+	if (m_bIsInitialized) {
+		clear();
+	}
+
+	// hardcopy geometries
+	m_pProjectionGeometry = _pProjectionGeometry->clone();
+	m_pVolumeGeometry = _pVolumeGeometry->clone();
+
+	// success
+	m_bIsInitialized = _check();
+	return m_bIsInitialized;
+}
+
+//----------------------------------------------------------------------------------------
+// Get maximum amount of weights on a single ray
+int CParallelBeamDistanceDrivenProjector2D::getProjectionWeightsCount(int _iProjectionIndex)
+{
+	int maxDim = max(m_pVolumeGeometry->getGridRowCount(), m_pVolumeGeometry->getGridColCount());
+	int scale = m_pProjectionGeometry->getDetectorWidth() / min(m_pVolumeGeometry->getPixelLengthX(), m_pVolumeGeometry->getPixelLengthY());
+	return maxDim * scale * 10 + 1;
+}
+
+//----------------------------------------------------------------------------------------
+// Single Ray Weights
+void CParallelBeamDistanceDrivenProjector2D::computeSingleRayWeights(int _iProjectionIndex, 
+														   int _iDetectorIndex, 
+														   SPixelWeight* _pWeightedPixels,
+														   int _iMaxPixelCount, 
+														   int& _iStoredPixelCount)
+{
+	ASTRA_ASSERT(m_bIsInitialized);
+	StorePixelWeightsPolicy p(_pWeightedPixels, _iMaxPixelCount);
+	projectSingleRay(_iProjectionIndex, _iDetectorIndex, p);
+	_iStoredPixelCount = p.getStoredPixelCount();
+}
+
+//----------------------------------------------------------------------------------------
+// Splat a single point
+std::vector<SDetector2D> CParallelBeamDistanceDrivenProjector2D::projectPoint(int _iRow, int _iCol)
+{
+	// TODO
+	assert(false);
+
+	std::vector<SDetector2D> res;
+
+	// return result vector
+	return res;
+
+}