Merge pull request #214 from harishkumar-harihara/add-stacked-backproject

add stacked-backproject

7 files changed, 1217 insertions, 0 deletions

diff --git a/docs/filters.rst b/docs/filters.rst
index f2b32ec..bbdc335 100644
--- a/docs/filters.rst
+++ b/docs/filters.rst
@@ -1096,6 +1096,67 @@ Tomographic backprojection
         Height of the region of interest. The default value of 0 denotes full
         height.
 
+Tomographic Stacked backprojection
+----------------------------------
+
+.. gobj:class:: stacked-backproject
+
+    Computes the backprojection of multiple sinograms in parallel.
+    Stream multiple sinograms by introducing a stack filter of certain size
+    before this filter.
+    A suitable minimum stack size must be specified based on precision mode
+
+    1. single - 2
+    2. half   - 4
+    3. int8   - 4
+
+    .. gobj:prop:: num-projections:uint
+
+        Number of projections between 0 and 180 degrees
+
+    .. gobj:prop:: offset:uint
+
+        Offset to the first projection.
+
+    .. gobj:prop:: axis-pos:double
+
+        Position of the rotation axis in horizontal pixel dimension of a
+        sinogram or projection. If not given, the center of the sinogram is
+        assumed.
+
+    .. gobj:prop:: angle-step:double
+
+        Angle step increment in radians. If not given, pi divided by height
+        of input sinogram is assumed.
+
+    .. gobj:prop:: angle-offset:double
+
+        Constant angle offset in radians. This determines effectively the
+        starting angle.
+
+    .. gobj:prop:: roi-x:uint
+
+        Horizontal coordinate of the start of the ROI. By default 0.
+
+    .. gobj:prop:: roi-y:uint
+
+        Vertical coordinate of the start of the ROI. By default 0.
+
+    .. gobj:prop:: roi-width:uint
+
+        Width of the region of interest. The default value of 0 denotes full
+        width.
+
+    .. gobj:prop:: roi-height:uint
+
+        Height of the region of interest. The default value of 0 denotes full
+        height.
+
+    .. gobj:prop:: precision-mode:enum
+
+        Precision mode or storage format which can be ``single`` or ``half``
+        or ``int8``
+        Correspondingly it represents storage in 32, 16 and 8-bits.
 
 Forward projection
 ------------------
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5fcafca..6295562 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -79,6 +79,7 @@ set(ufofilter_SRCS
     ufo-slice-task.c
     ufo-sliding-stack-task.c
     ufo-stack-task.c
+    ufo-stacked-backproject-task.c
     ufo-stdin-task.c
     ufo-stitch-task.c
     ufo-tile-task.c
diff --git a/src/kernels/meson.build b/src/kernels/meson.build
index f8a685c..bf61d77 100644
--- a/src/kernels/meson.build
+++ b/src/kernels/meson.build
@@ -42,6 +42,7 @@ kernel_files = [
     'rotate.cl',
     'segment.cl',
     'split.cl',
+    'stacked-backproject.cl',
     'swap-quadrants.cl',
     'transpose.cl',
     'zeropad.cl',
diff --git a/src/kernels/stacked-backproject.cl b/src/kernels/stacked-backproject.cl
new file mode 100644
index 0000000..d6fff5f
--- /dev/null
+++ b/src/kernels/stacked-backproject.cl
@@ -0,0 +1,381 @@
+/*
+ * Copyright (C) 2011-2013 Karlsruhe Institute of Technology
+ *
+ * This file is part of Ufo.
+ *
+ * This library is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+constant sampler_t volumeSampler_single = CLK_NORMALIZED_COORDS_FALSE |
+                                          CLK_ADDRESS_CLAMP |
+                                          CLK_FILTER_LINEAR;
+
+constant sampler_t volumeSampler_half = CLK_NORMALIZED_COORDS_FALSE |
+                                          CLK_ADDRESS_CLAMP |
+                                          CLK_FILTER_NEAREST;
+
+constant sampler_t volumeSampler_int8 = CLK_NORMALIZED_COORDS_FALSE |
+                                      CLK_ADDRESS_CLAMP_TO_EDGE |
+                                      CLK_FILTER_NEAREST;
+
+kernel void
+interleave_single ( global float *sinogram,
+                    write_only image2d_array_t interleaved_sinograms)
+{
+    const int idx = get_global_id(0);
+    const int idy = get_global_id(1);
+    const int idz = get_global_id(2);
+    const int sizex = get_global_size(0);
+    const int sizey = get_global_size(1);
+
+    int sinogram_offset = idz*2;
+
+    float x = sinogram[idx + idy * sizex + (sinogram_offset) * sizex * sizey];
+    float y = sinogram[idx + idy * sizex + (sinogram_offset+1) * sizex * sizey];
+
+    write_imagef(interleaved_sinograms, (int4)(idx, idy, idz, 0),(float4)(x,y,0.0f,0.0f));
+}
+
+kernel void
+texture_single (
+        read_only image2d_array_t sinogram,
+        global float2 *reconstructed_buffer,
+        constant float *sin_lut,
+        constant float *cos_lut,
+        const unsigned int x_offset,
+        const unsigned int y_offset,
+        const unsigned int angle_offset,
+        const unsigned int n_projections,
+        const float axis_pos,
+        unsigned long size){
+
+        const int local_idx = get_local_id(0);
+        const int local_idy = get_local_id(1);
+
+        const int global_idx = get_global_id(0);
+        const int global_idy = get_global_id(1);
+        const int idz = get_global_id(2);
+
+        int local_sizex = get_local_size(0);
+        int local_sizey = get_local_size(1);
+
+        int global_sizex = get_global_size(0);
+        int global_sizey = get_global_size(1);
+
+        /* Computing sequential numbers of 4x4 square, quadrant, and pixel within quadrant */
+        int square = local_idy%4;
+        int quadrant = local_idx/4;
+        int pixel = local_idx%4;
+
+        /* Computing projection and pixel offsets */
+        int projection_index = local_idy/4;
+
+        int2 remapped_index_local   = {(4*square + 2*(quadrant%2) + (pixel%2)),
+                                       (2* (quadrant/2) + (pixel/2))};
+
+        int2 remapped_index_global  = {(get_group_id(0)*get_local_size(0)+remapped_index_local.x),
+                                        (get_group_id(1)*get_local_size(1)+remapped_index_local.y)};
+
+        float2 pixel_coord = {(remapped_index_global.x - axis_pos + x_offset + 0.5f),
+                              (remapped_index_global.y - axis_pos + y_offset+0.5f)}; //bx and by
+
+        float2 sum[4] = {0.0f,0.0f};
+        __local float2 shared_mem[64][4];
+        __local float2 reconstructed_cache[16][16];
+
+
+        for(int proj = projection_index; proj < n_projections; proj+=4) {
+            float sine_value = sin_lut[angle_offset + proj];
+            float h = pixel_coord.x * cos_lut[angle_offset + proj] - pixel_coord.y * sin_lut[angle_offset + proj] + axis_pos;
+            for(int q=0; q<4; q+=1){
+                   sum[q] += read_imagef(sinogram, volumeSampler_single, (float4)(h-4*q*sine_value, proj + 0.5f,idz, 0.0)).xy;
+            }
+        }
+
+        int2 remapped_index = {(local_idx%4), (4*local_idy + (local_idx/4))};
+
+        for(int q=0; q<4;q+=1){
+            /* Moving partial sums to shared memory */
+            shared_mem[(local_sizex*remapped_index_local.y + remapped_index_local.x)][projection_index] = sum[q];
+
+            barrier(CLK_LOCAL_MEM_FENCE); // syncthreads
+
+            for(int i=2; i>=1; i/=2){
+                if(remapped_index.x <i){
+                    shared_mem[remapped_index.y][remapped_index.x] += shared_mem[remapped_index.y][remapped_index.x+i];
+                }
+                barrier(CLK_GLOBAL_MEM_FENCE); // syncthreads
+            }
+
+            if(remapped_index.x == 0){
+                reconstructed_cache[4*q+remapped_index.y/16][remapped_index.y%16] = shared_mem[remapped_index.y][0];
+            }
+            barrier(CLK_LOCAL_MEM_FENCE); // syncthreads
+        }
+
+        reconstructed_buffer[global_idx + global_idy*size + idz*size*size] = reconstructed_cache[local_idy][local_idx] * M_PI_F / n_projections;
+}
+
+kernel void
+uninterleave_single (global float2 *reconstructed_buffer,
+                global float *output)
+{
+    const int idx = get_global_id(0);
+    const int idy = get_global_id(1);
+    const int idz = get_global_id(2);
+    const int sizex = get_global_size(0);
+    const int sizey = get_global_size(1);
+    int output_offset = idz*2;
+
+    output[idx + idy*sizex + (output_offset)*sizex*sizey] = reconstructed_buffer[idx + idy*sizex + idz*sizex*sizey].x;
+    output[idx + idy*sizex + (output_offset+1)*sizex*sizey] = reconstructed_buffer[idx + idy*sizex + idz*sizex*sizey].y;
+}
+
+kernel void
+interleave_half (global float *sinogram,
+                 write_only image2d_array_t interleaved_sinograms)
+{
+    const int idx = get_global_id(0);
+    const int idy = get_global_id(1);
+    const int idz = get_global_id(2);
+    const int sizex = get_global_size(0);
+    const int sizey = get_global_size(1);
+
+    int sinogram_offset = idz*4;
+
+    float4 b = {sinogram[idx + idy * sizex + (sinogram_offset) * sizex * sizey],
+                sinogram[idx + idy * sizex + (sinogram_offset+1) * sizex * sizey],
+                sinogram[idx + idy * sizex + (sinogram_offset+2) * sizex * sizey],
+                sinogram[idx + idy * sizex + (sinogram_offset+3) * sizex * sizey]};
+
+    // At each pixel, pack 4 slices in Z-projection
+    write_imagef(interleaved_sinograms, (int4)(idx, idy, idz, 0),(float4)(b));
+}
+
+kernel void
+texture_half (
+        read_only image2d_array_t sinogram,
+        global float4 *reconstructed_buffer,
+        constant float *sin_lut,
+        constant float *cos_lut,
+        const unsigned int x_offset,
+        const unsigned int y_offset,
+        const unsigned int angle_offset,
+        const unsigned int n_projections,
+        const float axis_pos,
+        unsigned long size){
+
+    const int local_idx = get_local_id(0);
+    const int local_idy = get_local_id(1);
+
+    const int global_idx = get_global_id(0);
+    const int global_idy = get_global_id(1);
+    const int idz = get_global_id(2);
+
+    int local_sizex = get_local_size(0);
+    int local_sizey = get_local_size(1);
+
+    int global_sizex = get_global_size(0);
+    int global_sizey = get_global_size(1);
+
+    /* Computing sequential numbers of 4x4 square, quadrant, and pixel within quadrant */
+    int square = local_idy%4;
+    int quadrant = local_idx/4;
+    int pixel = local_idx%4;
+
+    /* Computing projection and pixel offsets */
+    int projection_index = local_idy/4;
+    int2 remapped_index_local   = {(4*square + 2*(quadrant%2) + (pixel%2)),(2* (quadrant/2) + (pixel/2))};
+    int2 remapped_index_global  = {(get_group_id(0)*get_local_size(0)+remapped_index_local.x),
+                                    (get_group_id(1)*get_local_size(1)+remapped_index_local.y)};
+
+
+    float2 pixel_coord = {(remapped_index_global.x-axis_pos+x_offset+0.5f), (remapped_index_global.y-axis_pos+y_offset+0.5f)}; //bx and by
+    float4 sum[4] = {0.0f,0.0f,0.0f,0.0f};
+    __local float4 shared_mem[64][4];
+    __local float4 reconstructed_cache[16][16];
+
+
+    for(int proj = projection_index; proj < n_projections; proj+=4) {
+        float sine_value = sin_lut[angle_offset + proj];
+        float h = pixel_coord.x * cos_lut[angle_offset + proj] - pixel_coord.y * sin_lut[angle_offset + proj] + axis_pos;
+        for(int q=0; q<4; q+=1){
+           sum[q] += read_imagef(sinogram, volumeSampler_half, (float4)(h-4*q*sine_value, proj + 0.5f,idz, 0.0));
+        }
+    }
+
+    int2 remapped_index = {(local_idx%4), (4*local_idy + (local_idx/4))};
+
+    for(int q=0; q<4;q+=1){
+        /* Moving partial sums to shared memory */
+        shared_mem[(local_sizex*remapped_index_local.y + remapped_index_local.x)][projection_index] = sum[q];
+
+        barrier(CLK_LOCAL_MEM_FENCE); // syncthreads
+
+        for(int i=2; i>=1; i/=2){
+            if(remapped_index.x <i){
+                shared_mem[remapped_index.y][remapped_index.x] += shared_mem[remapped_index.y][remapped_index.x+i];
+            }
+            barrier(CLK_GLOBAL_MEM_FENCE); // syncthreads
+        }
+
+        if(remapped_index.x == 0){
+            reconstructed_cache[4*q+remapped_index.y/16][remapped_index.y%16] = shared_mem[remapped_index.y][0];
+        }
+        barrier(CLK_LOCAL_MEM_FENCE); // syncthreads
+    }
+    reconstructed_buffer[global_idx + global_idy*size + idz*size*size] = reconstructed_cache[local_idy][local_idx] * M_PI_F / n_projections;
+}
+
+kernel void
+uninterleave_half (global float4 *reconstructed_buffer,
+                   global float *output)
+{
+    const int idx = get_global_id(0);
+    const int idy = get_global_id(1);
+    const int idz = get_global_id(2);
+    const int sizex = get_global_size(0);
+    const int sizey = get_global_size(1);
+
+    int output_offset = idz*4;
+
+    float4 b = reconstructed_buffer[idx + idy*sizex + idz*sizex*sizey];
+
+    output[idx + idy*sizex + (output_offset)*sizex*sizey] = b.x;
+    output[idx + idy*sizex + (output_offset+1)*sizex*sizey] = b.y;
+    output[idx + idy*sizex + (output_offset+2)*sizex*sizey] = b.z;
+    output[idx + idy*sizex + (output_offset+3)*sizex*sizey] = b.w;
+}
+
+kernel void
+interleave_uint (global float *sinogram,
+            write_only image2d_array_t interleaved_sinograms,
+            const float min,
+            const float max)
+{
+    const int idx = get_global_id(0);
+    const int idy = get_global_id(1);
+    const int idz = get_global_id(2);
+    const int sizex = get_global_size(0);
+    const int sizey = get_global_size(1);
+
+    int sinogram_offset = idz*4;
+
+    const float scale = 255.0f / (max - min);
+
+    uint4 b = {(sinogram[idx + idy * sizex + (sinogram_offset) * sizex * sizey] - min)*scale,
+               (sinogram[idx + idy * sizex + (sinogram_offset+1) * sizex * sizey] - min)*scale,
+               (sinogram[idx + idy * sizex + (sinogram_offset+2) * sizex * sizey] - min)*scale,
+               (sinogram[idx + idy * sizex + (sinogram_offset+3) * sizex * sizey] - min)*scale};
+
+   write_imageui(interleaved_sinograms, (int4)(idx, idy, idz, 0),(uint4)(b));
+}
+
+kernel void
+texture_uint (
+        read_only image2d_array_t sinogram,
+        global uint4 *reconstructed_buffer,
+        constant float *sin_lut,
+        constant float *cos_lut,
+        const unsigned int x_offset,
+        const unsigned int y_offset,
+        const unsigned int angle_offset,
+        const unsigned int n_projections,
+        const float axis_pos,
+        unsigned long size){
+
+        const int local_idx = get_local_id(0);
+        const int local_idy = get_local_id(1);
+
+        const int global_idx = get_global_id(0);
+        const int global_idy = get_global_id(1);
+        const int idz = get_global_id(2);
+
+        int local_sizex = get_local_size(0);
+        int local_sizey = get_local_size(1);
+
+        int global_sizex = get_global_size(0);
+        int global_sizey = get_global_size(1);
+
+        /* Computing sequential numbers of 4x4 square, quadrant, and pixel within quadrant */
+        int square = local_idy%4;
+        int quadrant = local_idx/4;
+        int pixel = local_idx%4;
+
+        /* Computing projection and pixel offsets */
+        int projection_index = local_idy/4;
+        int2 remapped_index_local   = {(4*square + 2*(quadrant%2) + (pixel%2)),(2* (quadrant/2) + (pixel/2))};
+        int2 remapped_index_global  = {(get_group_id(0)*get_local_size(0)+remapped_index_local.x),
+                                        (get_group_id(1)*get_local_size(1)+remapped_index_local.y)};
+
+        float2 pixel_coord = {(remapped_index_global.x-axis_pos+x_offset+0.5f), (remapped_index_global.y-axis_pos+y_offset+0.5f)}; //bx and by
+
+        uint4 sum[4] = {0,0,0,0};
+        __local uint4 shared_mem[64][4];
+        __local uint4 reconstructed_cache[16][16];
+
+        for(int proj = projection_index; proj < n_projections; proj+=4) {
+            float sine_value = sin_lut[angle_offset + proj];
+            float h = pixel_coord.x * cos_lut[angle_offset + proj] - pixel_coord.y * sin_lut[angle_offset + proj] + axis_pos;
+            for(int q=0; q<4; q+=1){
+               sum[q] += read_imageui(sinogram, volumeSampler_int8, (float4)(h-4*q*sine_value, proj + 0.5f,idz, 0.0));
+            }
+        }
+
+
+        int2 remapped_index = {(local_idx%4), (4*local_idy + (local_idx/4))};
+
+        for(int q=0; q<4;q+=1){
+            /* Moving partial sums to shared memory */
+            shared_mem[(local_sizex*remapped_index_local.y + remapped_index_local.x)][projection_index] = sum[q];
+
+            barrier(CLK_LOCAL_MEM_FENCE); // syncthreads
+
+            for(int i=2; i>=1; i/=2){
+                if(remapped_index.x <i){
+                    shared_mem[remapped_index.y][remapped_index.x] += shared_mem[remapped_index.y][remapped_index.x+i];
+                }
+                barrier(CLK_GLOBAL_MEM_FENCE); // syncthreads
+            }
+
+            if(remapped_index.x == 0){
+                reconstructed_cache[4*q+remapped_index.y/16][remapped_index.y%16] = shared_mem[remapped_index.y][0];
+            }
+            barrier(CLK_LOCAL_MEM_FENCE); // syncthreads
+        }
+
+        reconstructed_buffer[global_idx + global_idy*size + idz*size*size] = reconstructed_cache[local_idy][local_idx];
+}
+
+kernel void
+uninterleave_uint (global uint4 *reconstructed_buffer,
+                global float *output,
+                const float min,
+                const float max,
+                const unsigned int n_projections)
+{
+    const int idx = get_global_id(0);
+    const int idy = get_global_id(1);
+    const int idz = get_global_id(2);
+    const int sizex = get_global_size(0);
+    const int sizey = get_global_size(1);
+
+    int output_offset = idz*4;
+    float scale = (max-min)/255.0f;
+
+    output[idx + idy*sizex + (output_offset)*sizex*sizey] = ((reconstructed_buffer[idx + idy*sizex + idz*sizex*sizey].x)*scale+min)* M_PI_F / n_projections;
+    output[idx + idy*sizex + (output_offset+1)*sizex*sizey] = ((reconstructed_buffer[idx + idy*sizex + idz*sizex*sizey].y)*scale+min)* M_PI_F / n_projections;
+    output[idx + idy*sizex + (output_offset+2)*sizex*sizey] = ((reconstructed_buffer[idx + idy*sizex + idz*sizex*sizey].z)*scale+min)* M_PI_F / n_projections;
+    output[idx + idy*sizex + (output_offset+3)*sizex*sizey] = ((reconstructed_buffer[idx + idy*sizex + idz*sizex*sizey].w)*scale+min)* M_PI_F / n_projections;
+}
\ No newline at end of file
diff --git a/src/meson.build b/src/meson.build
index 28054c6..d3f2c09 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -68,6 +68,7 @@ plugins = [
     'slice',
     'sliding-stack',
     'stack',
+    'stacked-backproject',
     'stitch',
     'stdin',
     'tile',
diff --git a/src/ufo-stacked-backproject-task.c b/src/ufo-stacked-backproject-task.c
new file mode 100644
index 0000000..5ddfd26
--- /dev/null
+++ b/src/ufo-stacked-backproject-task.c
@@ -0,0 +1,719 @@
+/*
+ * Copyright (C) 2011-2015 Karlsruhe Institute of Technology
+ *
+ * This file is part of Ufo.
+ *
+ * This library is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+#ifdef __APPLE__
+#include <OpenCL/cl.h>
+#else
+#include <CL/cl.h>
+#endif
+
+#include <stdio.h>
+#include <math.h>
+#include "ufo-stacked-backproject-task.h"
+
+typedef enum {
+    INT8,
+    HALF,
+    SINGLE
+} Precision;
+
+static GEnumValue precision_values[] = {
+        {INT8,"INT8","int8"},
+        {HALF, "HALF", "half"},
+        {SINGLE, "SINGLE", "single"},
+        { 0, NULL, NULL}
+};
+
+struct _UfoStackedBackprojectTaskPrivate {
+    cl_context context;
+    cl_kernel interleave_single;
+    cl_kernel interleave_half;
+    cl_kernel interleave_uint;
+    cl_kernel uninterleave_single;
+    cl_kernel uninterleave_half;
+    cl_kernel uninterleave_uint;
+    cl_kernel texture_single;
+    cl_kernel texture_half;
+    cl_kernel texture_uint;
+    cl_mem sin_lut;
+    cl_mem cos_lut;
+    gfloat *host_sin_lut;
+    gfloat *host_cos_lut;
+    gdouble axis_pos;
+    gdouble angle_step;
+    gdouble angle_offset;
+    gdouble real_angle_step;
+    gboolean luts_changed;
+    guint offset;
+    guint burst_projections;
+    guint n_projections;
+    guint roi_x;
+    guint roi_y;
+    gint roi_width;
+    gint roi_height;
+    Precision precision;
+};
+
+static void ufo_task_interface_init (UfoTaskIface *iface);
+
+G_DEFINE_TYPE_WITH_CODE (UfoStackedBackprojectTask, ufo_stacked_backproject_task, UFO_TYPE_TASK_NODE,
+        G_IMPLEMENT_INTERFACE (UFO_TYPE_TASK,
+                               ufo_task_interface_init))
+
+#define UFO_STACKED_BACKPROJECT_TASK_GET_PRIVATE(obj) (G_TYPE_INSTANCE_GET_PRIVATE((obj), UFO_TYPE_STACKED_BACKPROJECT_TASK, UfoStackedBackprojectTaskPrivate))
+
+enum {
+    PROP_0,
+    PROP_NUM_PROJECTIONS,
+    PROP_OFFSET,
+    PROP_AXIS_POSITION,
+    PROP_ANGLE_STEP,
+    PROP_ANGLE_OFFSET,
+    PROP_ROI_X,
+    PROP_ROI_Y,
+    PROP_ROI_WIDTH,
+    PROP_ROI_HEIGHT,
+    PROP_PRECISION,
+    N_PROPERTIES
+};
+
+static GParamSpec *properties[N_PROPERTIES] = { NULL, };
+
+UfoNode *
+ufo_stacked_backproject_task_new (void)
+{
+    return UFO_NODE (g_object_new (UFO_TYPE_STACKED_BACKPROJECT_TASK, NULL));
+}
+
+static void
+ufo_stacked_backproject_task_setup (UfoTask *task,
+                                    UfoResources *resources,
+                                    GError **error)
+{
+    UfoStackedBackprojectTaskPrivate *priv;
+
+    priv = UFO_STACKED_BACKPROJECT_TASK_GET_PRIVATE(task);
+
+    priv->context = ufo_resources_get_context(resources);
+
+    priv->interleave_single = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "interleave_single", NULL, error);
+    priv->texture_single = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "texture_single", NULL, error);
+    priv->uninterleave_single = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "uninterleave_single", NULL, error);
+
+    priv->interleave_half = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "interleave_half", NULL, error);
+    priv->texture_half = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "texture_half", NULL, error);
+    priv->uninterleave_half = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "uninterleave_half", NULL, error);
+
+    priv->interleave_uint = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "interleave_uint", NULL, error);
+    priv->texture_uint = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "texture_uint", NULL, error);
+    priv->uninterleave_uint = ufo_resources_get_kernel (resources, "stacked-backproject.cl", "uninterleave_uint", NULL, error);
+
+    UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainContext (priv->context), error);
+
+    if (priv->interleave_single != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->interleave_single), error);
+
+    if (priv->interleave_half != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->interleave_half), error);
+
+    if (priv->interleave_uint != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->interleave_uint), error);
+
+    if (priv->uninterleave_single != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->uninterleave_single), error);
+
+    if (priv->uninterleave_half != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->uninterleave_half), error);
+
+    if (priv->uninterleave_uint != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->uninterleave_uint), error);
+
+    if (priv->texture_single != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->texture_single), error);
+
+    if (priv->texture_half != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->texture_half), error);
+
+    if (priv->texture_uint != NULL)
+        UFO_RESOURCES_CHECK_SET_AND_RETURN (clRetainKernel (priv->texture_uint), error);
+}
+
+static cl_mem
+create_lut_buffer (UfoStackedBackprojectTaskPrivate *priv,
+                   gfloat **host_mem,
+                   gsize n_entries,
+                   double (*func)(double))
+{
+    cl_int errcode;
+    gsize size = n_entries * sizeof (gfloat);
+    cl_mem mem = NULL;
+
+    *host_mem = g_realloc (*host_mem, size);
+
+    for (guint i = 0; i < n_entries; i++)
+        (*host_mem)[i] = (gfloat) func (priv->angle_offset + i * priv->real_angle_step);
+
+    mem = clCreateBuffer (priv->context,
+                          CL_MEM_COPY_HOST_PTR | CL_MEM_READ_ONLY,
+                          size, *host_mem,
+                          &errcode);
+
+    UFO_RESOURCES_CHECK_CLERR (errcode);
+    return mem;
+}
+
+static void
+release_lut_mems (UfoStackedBackprojectTaskPrivate *priv)
+{
+    if (priv->sin_lut) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseMemObject (priv->sin_lut));
+        priv->sin_lut = NULL;
+    }
+
+    if (priv->cos_lut) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseMemObject (priv->cos_lut));
+        priv->cos_lut = NULL;
+    }
+}
+
+static void
+ufo_stacked_backproject_task_get_requisition (UfoTask *task,
+                                              UfoBuffer **inputs,
+                                              UfoRequisition *requisition,
+                                              GError **error)
+{
+    UfoStackedBackprojectTaskPrivate *priv;
+    UfoRequisition in_req;
+
+    priv = UFO_STACKED_BACKPROJECT_TASK_GET_PRIVATE(task);
+    ufo_buffer_get_requisition(inputs[0],&in_req);
+
+    /* If the number of projections is not specified use the input size */
+    if (priv->n_projections == 0) {
+        priv->n_projections = (guint) in_req.dims[1];
+    }
+
+    priv->burst_projections = (guint) in_req.dims[1];
+
+    if (priv->burst_projections > priv->n_projections) {
+        g_set_error (error, UFO_TASK_ERROR, UFO_TASK_ERROR_GET_REQUISITION,
+                     "Total number of projections (%u) must be greater than "
+                     "or equal to sinogram height (%u)",
+                     priv->n_projections, priv->burst_projections);
+        return;
+    }
+
+    requisition->n_dims = 3;
+
+    /* TODO: we should check here, that we might access data outside the projections */
+
+    requisition->dims[0] = priv->roi_width == 0 ? in_req.dims[0] : (gsize) priv->roi_width;
+    requisition->dims[1] = priv->roi_height == 0 ? in_req.dims[0] : (gsize) priv->roi_height;
+    requisition->dims[2] = in_req.n_dims == 3 ? in_req.dims[2]:1;
+
+    if (priv->real_angle_step < 0.0) {
+        if (priv->angle_step <= 0.0)
+            priv->real_angle_step = G_PI / ((gdouble) priv->n_projections);
+        else
+            priv->real_angle_step = priv->angle_step;
+    }
+
+    if (priv->luts_changed) {
+        release_lut_mems (priv);
+        priv->luts_changed = FALSE;
+    }
+
+    if (priv->sin_lut == NULL) {
+        priv->sin_lut = create_lut_buffer (priv, &priv->host_sin_lut,
+                                           priv->n_projections, sin);
+    }
+
+    if (priv->cos_lut == NULL) {
+        priv->cos_lut = create_lut_buffer (priv, &priv->host_cos_lut,
+                                           priv->n_projections, cos);
+    }
+}
+
+static guint
+ufo_stacked_backproject_task_get_num_inputs (UfoTask *task)
+{
+    return 1;
+}
+
+static guint
+ufo_stacked_backproject_task_get_num_dimensions (UfoTask *task,
+                                                 guint input)
+{
+    g_return_val_if_fail (input == 0, 0);
+    return 3;
+}
+
+static UfoTaskMode
+ufo_stacked_backproject_task_get_mode (UfoTask *task)
+{
+    return UFO_TASK_MODE_PROCESSOR | UFO_TASK_MODE_GPU;
+}
+
+static gboolean
+ufo_stacked_backproject_task_equal_real (UfoNode *n1,
+                                         UfoNode *n2)
+{
+    g_return_val_if_fail (UFO_IS_STACKED_BACKPROJECT_TASK (n1) && UFO_IS_STACKED_BACKPROJECT_TASK (n2), FALSE);
+    return UFO_STACKED_BACKPROJECT_TASK (n1)->priv->texture_single == UFO_STACKED_BACKPROJECT_TASK (n2)->priv->texture_single;
+}
+
+
+static gboolean
+ufo_stacked_backproject_task_process (UfoTask *task,
+                                      UfoBuffer **inputs,
+                                      UfoBuffer *output,
+                                      UfoRequisition *requisition)
+{
+    UfoStackedBackprojectTaskPrivate *priv;
+    UfoGpuNode *node;
+    UfoProfiler *profiler;
+    cl_command_queue cmd_queue;
+    cl_mem interleaved_img;
+    cl_mem out_mem;
+    cl_mem reconstructed_buffer;
+    cl_mem device_array;
+
+    cl_kernel kernel_interleave;
+    cl_kernel kernel_texture;
+    cl_kernel kernel_uninterleave;
+
+    size_t buffer_size;
+    gfloat axis_pos;
+
+    priv = UFO_STACKED_BACKPROJECT_TASK(task)->priv;
+    node = UFO_GPU_NODE (ufo_task_node_get_proc_node(UFO_TASK_NODE(task)));
+    cmd_queue = ufo_gpu_node_get_cmd_queue(node);
+    out_mem = ufo_buffer_get_device_array (output, cmd_queue);
+    profiler = ufo_task_node_get_profiler (UFO_TASK_NODE (task));
+
+    /* Guess axis position if they are not provided by the user. */
+    if (priv->axis_pos <= 0.0) {
+        UfoRequisition in_req;
+
+        ufo_buffer_get_requisition(inputs[0], &in_req);
+        axis_pos = (gfloat) ((gfloat) in_req.dims[0]) / 2.0f;
+    } else {
+        axis_pos = priv->axis_pos;
+    }
+
+    // Image format
+    cl_image_format format;
+    device_array = ufo_buffer_get_device_array(inputs[0],cmd_queue);
+
+    UfoRequisition req;
+    ufo_buffer_get_requisition(inputs[0],&req);
+
+    unsigned long dim_x = (requisition->dims[0]%16 == 0) ? requisition->dims[0] : (((requisition->dims[0]/16)+1)*16);
+    unsigned long dim_y = (requisition->dims[1]%16 == 0) ? requisition->dims[1] : (((requisition->dims[1]/16)+1)*16);
+    unsigned long quotient;
+
+    // reconstructs in 3 precision modes
+    // 2 slices are reconstructed for single precision, else reconstructs 4 slices in parallel
+    if(priv->precision == SINGLE){
+        quotient = requisition->dims[2]/2;
+        kernel_interleave = priv->interleave_single;
+        kernel_texture = priv->texture_single;
+        kernel_uninterleave = priv->uninterleave_single;
+        format.image_channel_order = CL_RG;
+        format.image_channel_data_type = CL_FLOAT;
+        buffer_size = sizeof(cl_float2) * dim_x * dim_y * quotient;
+    }else if(priv->precision == HALF){
+        quotient = requisition->dims[2]/4;
+        kernel_interleave = priv->interleave_half;
+        kernel_texture = priv->texture_half;
+        kernel_uninterleave = priv->uninterleave_half;
+        format.image_channel_order = CL_RGBA;
+        buffer_size = sizeof(cl_float4) * dim_x * dim_y * quotient;
+        format.image_channel_data_type = CL_HALF_FLOAT;
+    }else if(priv->precision == INT8){
+        quotient = requisition->dims[2]/4;
+        kernel_interleave = priv->interleave_uint;
+        kernel_texture = priv->texture_uint;
+        kernel_uninterleave = priv->uninterleave_uint;
+        format.image_channel_order = CL_RGBA;
+        format.image_channel_data_type = CL_UNSIGNED_INT8;
+        buffer_size = sizeof(cl_uint4) * dim_x * dim_y * quotient;
+    }
+
+    cl_image_desc imageDesc;
+    imageDesc.image_width = req.dims[0];
+    imageDesc.image_height = req.dims[1];
+    imageDesc.image_depth = 0;
+    imageDesc.image_array_size = quotient;
+    imageDesc.image_type = CL_MEM_OBJECT_IMAGE2D_ARRAY;
+    imageDesc.image_slice_pitch = 0;
+    imageDesc.image_row_pitch = 0;
+    imageDesc.num_mip_levels = 0;
+    imageDesc.num_samples = 0;
+    imageDesc.buffer = NULL;
+
+    float max_element;
+    float min_element;
+
+    if(quotient > 0) {
+        // Interleave
+        interleaved_img = clCreateImage(priv->context, CL_MEM_READ_WRITE, &format, &imageDesc, NULL, 0);
+
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_interleave, 0, sizeof(cl_mem), &device_array));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_interleave, 1, sizeof(cl_mem), &interleaved_img));
+        if(priv->precision == INT8){
+            //Normalize i.e convert float array to 0-255
+            float *host = ufo_buffer_get_host_array(inputs[0],cmd_queue);
+            min_element = ufo_buffer_min(inputs[0],cmd_queue);
+            max_element = ufo_buffer_max(inputs[0],cmd_queue);
+
+            UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_interleave, 2, sizeof(float), &min_element));
+            UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_interleave, 3, sizeof(float), &max_element));
+        }
+
+        size_t gsize_interleave[3] = {req.dims[0],req.dims[1],quotient};
+        ufo_profiler_call(profiler, cmd_queue, kernel_interleave, 3, gsize_interleave, NULL);
+
+        // SINOGRAM RECONSTRUCTION FOR MULTIPLE SLICES
+        reconstructed_buffer = clCreateBuffer(priv->context, CL_MEM_READ_WRITE, buffer_size, NULL, 0);
+
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 0, sizeof(cl_mem), &interleaved_img));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 1, sizeof(cl_mem), &reconstructed_buffer));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 2, sizeof(cl_mem), &priv->sin_lut));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 3, sizeof(cl_mem), &priv->cos_lut));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 4, sizeof(guint), &priv->roi_x));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 5, sizeof(guint), &priv->roi_y));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 6, sizeof(guint), &priv->offset));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 7, sizeof(guint), &priv->burst_projections));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 8, sizeof(gfloat), &axis_pos));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_texture, 9, sizeof(unsigned long), &requisition->dims[0]));
+
+        size_t gsize_texture[3] = {dim_x,dim_y,quotient};
+        size_t lSize[3] = {16,16,1};
+        ufo_profiler_call(profiler, cmd_queue, kernel_texture, 3, gsize_texture, lSize);
+
+        //UNINTERLEAVE
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_uninterleave, 0, sizeof(cl_mem), &reconstructed_buffer));
+        UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_uninterleave, 1, sizeof(cl_mem), &out_mem));
+        if(priv->precision == INT8){
+            UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_uninterleave, 2, sizeof(float), &min_element));
+            UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_uninterleave, 3, sizeof(float), &max_element));
+            UFO_RESOURCES_CHECK_CLERR(clSetKernelArg(kernel_uninterleave, 4, sizeof(guint), &priv->burst_projections));
+        }
+
+        size_t gsize_uninterleave[3] = {requisition->dims[0],requisition->dims[1],quotient};
+        ufo_profiler_call(profiler, cmd_queue, kernel_uninterleave, 3, gsize_uninterleave, NULL);
+
+        UFO_RESOURCES_CHECK_CLERR(clReleaseMemObject(interleaved_img));
+        UFO_RESOURCES_CHECK_CLERR(clReleaseMemObject(reconstructed_buffer));
+    }
+
+    return TRUE;
+}
+
+
+static void
+ufo_stacked_backproject_task_set_property (GObject *object,
+                                           guint property_id,
+                                           const GValue *value,
+                                           GParamSpec *pspec)
+{
+    UfoStackedBackprojectTaskPrivate *priv = UFO_STACKED_BACKPROJECT_TASK_GET_PRIVATE (object);
+
+    switch (property_id) {
+        case PROP_NUM_PROJECTIONS:
+            priv->n_projections = g_value_get_uint (value);
+            break;
+        case PROP_OFFSET:
+            priv->offset = g_value_get_uint (value);
+            break;
+        case PROP_AXIS_POSITION:
+            priv->axis_pos = g_value_get_double (value);
+            break;
+        case PROP_ANGLE_STEP:
+            priv->angle_step = g_value_get_double (value);
+            break;
+        case PROP_ANGLE_OFFSET:
+            priv->angle_offset = g_value_get_double (value);
+            priv->luts_changed = TRUE;
+            break;
+        case PROP_ROI_X:
+            priv->roi_x = g_value_get_uint (value);
+            break;
+        case PROP_ROI_Y:
+            priv->roi_y = g_value_get_uint (value);
+            break;
+        case PROP_ROI_WIDTH:
+            priv->roi_width = g_value_get_uint (value);
+            break;
+        case PROP_ROI_HEIGHT:
+            priv->roi_height = g_value_get_uint (value);
+            break;
+        case PROP_PRECISION:
+            priv->precision = g_value_get_enum(value);
+            break;
+        default:
+            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+            break;
+    }
+}
+
+static void
+ufo_stacked_backproject_task_get_property (GObject *object,
+                                           guint property_id,
+                                           GValue *value,
+                                           GParamSpec *pspec)
+{
+    UfoStackedBackprojectTaskPrivate *priv = UFO_STACKED_BACKPROJECT_TASK_GET_PRIVATE (object);
+
+    switch (property_id) {
+        case PROP_NUM_PROJECTIONS:
+            g_value_set_uint (value, priv->n_projections);
+            break;
+        case PROP_OFFSET:
+            g_value_set_uint (value, priv->offset);
+            break;
+        case PROP_AXIS_POSITION:
+            g_value_set_double (value, priv->axis_pos);
+            break;
+        case PROP_ANGLE_STEP:
+            g_value_set_double (value, priv->angle_step);
+            break;
+        case PROP_ANGLE_OFFSET:
+            g_value_set_double (value, priv->angle_offset);
+            break;
+        case PROP_ROI_X:
+            g_value_set_uint (value, priv->roi_x);
+            break;
+        case PROP_ROI_Y:
+            g_value_set_uint (value, priv->roi_y);
+            break;
+        case PROP_ROI_WIDTH:
+            g_value_set_uint (value, priv->roi_width);
+            break;
+        case PROP_ROI_HEIGHT:
+            g_value_set_uint (value, priv->roi_height);
+            break;
+        case PROP_PRECISION:
+            g_value_set_enum(value,priv->precision);
+            break;
+        default:
+            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+            break;
+    }
+}
+
+static void
+ufo_stacked_backproject_task_finalize (GObject *object)
+{
+    UfoStackedBackprojectTaskPrivate *priv;
+    priv = UFO_STACKED_BACKPROJECT_TASK_GET_PRIVATE(object);
+
+    release_lut_mems(priv);
+
+    g_free(priv->host_sin_lut);
+    g_free(priv->host_cos_lut);
+
+    if (priv->interleave_single) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->interleave_single));
+        priv->interleave_single = NULL;
+    }
+
+    if (priv->interleave_half) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->interleave_half));
+        priv->interleave_half = NULL;
+    }
+
+    if (priv->interleave_uint) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->interleave_uint));
+        priv->interleave_uint = NULL;
+    }
+
+    if (priv->uninterleave_single) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->uninterleave_single));
+        priv->uninterleave_single = NULL;
+    }
+
+    if (priv->uninterleave_half) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->uninterleave_half));
+        priv->uninterleave_half = NULL;
+    }
+
+    if (priv->uninterleave_uint) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->uninterleave_uint));
+        priv->uninterleave_uint = NULL;
+    }
+
+    if (priv->context) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseContext (priv->context));
+        priv->context = NULL;
+    }
+
+    if (priv->texture_single) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->texture_single));
+        priv->texture_single = NULL;
+    }
+
+    if (priv->texture_half) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->texture_half));
+        priv->texture_half = NULL;
+    }
+
+    if (priv->texture_uint) {
+        UFO_RESOURCES_CHECK_CLERR (clReleaseKernel (priv->texture_uint));
+        priv->texture_uint = NULL;
+    }
+
+    G_OBJECT_CLASS (ufo_stacked_backproject_task_parent_class)->finalize (object);
+}
+
+static void
+ufo_task_interface_init (UfoTaskIface *iface)
+{
+    iface->setup = ufo_stacked_backproject_task_setup;
+    iface->get_num_inputs = ufo_stacked_backproject_task_get_num_inputs;
+    iface->get_num_dimensions = ufo_stacked_backproject_task_get_num_dimensions;
+    iface->get_mode = ufo_stacked_backproject_task_get_mode;
+    iface->get_requisition = ufo_stacked_backproject_task_get_requisition;
+    iface->process = ufo_stacked_backproject_task_process;
+}
+
+
+static void
+ufo_stacked_backproject_task_class_init (UfoStackedBackprojectTaskClass *klass)
+{
+    GObjectClass *oclass = G_OBJECT_CLASS (klass);
+    UfoNodeClass *node_class;
+
+    oclass = G_OBJECT_CLASS (klass);
+    node_class = UFO_NODE_CLASS (klass);
+
+    oclass->set_property = ufo_stacked_backproject_task_set_property;
+    oclass->get_property = ufo_stacked_backproject_task_get_property;
+    oclass->finalize = ufo_stacked_backproject_task_finalize;
+
+    properties[PROP_NUM_PROJECTIONS] =
+            g_param_spec_uint ("num-projections",
+                               "Number of projections between 0 and 180 degrees",
+                               "Number of projections between 0 and 180 degrees",
+                               0, +32768, 0,
+                               G_PARAM_READWRITE);
+
+    properties[PROP_OFFSET] =
+            g_param_spec_uint ("offset",
+                               "Offset to the first projection",
+                               "Offset to the first projection",
+                               0, +32768, 0,
+                               G_PARAM_READWRITE);
+
+    properties[PROP_AXIS_POSITION] =
+            g_param_spec_double ("axis-pos",
+                                 "Position of rotation axis",
+                                 "Position of rotation axis",
+                                 -1.0, +32768.0, 0.0,
+                                 G_PARAM_READWRITE);
+
+    properties[PROP_ANGLE_STEP] =
+            g_param_spec_double ("angle-step",
+                                 "Increment of angle in radians",
+                                 "Increment of angle in radians",
+                                 -G_MAXDOUBLE, G_MAXDOUBLE, 0.0,
+                                 G_PARAM_READWRITE);
+
+    properties[PROP_ANGLE_OFFSET] =
+            g_param_spec_double ("angle-offset",
+                                 "Angle offset in radians",
+                                 "Angle offset in radians determining the first angle position",
+                                 0.0, G_MAXDOUBLE, 0.0,
+                                 G_PARAM_READWRITE);
+
+    properties[PROP_PRECISION] =
+            g_param_spec_enum("precision-mode",
+                              "Precision mode (\"int8\", \"half\", \"single\")",
+                              "Precision mode (\"int8\", \"half\", \"single\")",
+                              g_enum_register_static("ufo_stacked_backproject_precision", precision_values),
+                              SINGLE, G_PARAM_READWRITE);
+
+
+    properties[PROP_ROI_X] =
+            g_param_spec_uint ("roi-x",
+                               "X coordinate of region of interest",
+                               "X coordinate of region of interest",
+                               0, G_MAXUINT, 0,
+                               G_PARAM_READWRITE);
+
+    properties[PROP_ROI_Y] =
+            g_param_spec_uint ("roi-y",
+                               "Y coordinate of region of interest",
+                               "Y coordinate of region of interest",
+                               0, G_MAXUINT, 0,
+                               G_PARAM_READWRITE);
+
+    properties[PROP_ROI_WIDTH] =
+            g_param_spec_uint ("roi-width",
+                               "Width of region of interest",
+                               "Width of region of interest",
+                               0, G_MAXUINT, 0,
+                               G_PARAM_READWRITE);
+
+    properties[PROP_ROI_HEIGHT] =
+            g_param_spec_uint ("roi-height",
+                               "Height of region of interest",
+                               "Height of region of interest",
+                               0, G_MAXUINT, 0,
+                               G_PARAM_READWRITE);
+
+    for (guint i = PROP_0 + 1; i < N_PROPERTIES; i++)
+        g_object_class_install_property (oclass, i, properties[i]);
+
+    node_class->equal = ufo_stacked_backproject_task_equal_real;
+
+    g_type_class_add_private (oclass, sizeof(UfoStackedBackprojectTaskPrivate));
+}
+
+static void
+ufo_stacked_backproject_task_init(UfoStackedBackprojectTask *self)
+{
+    UfoStackedBackprojectTaskPrivate *priv;
+    self->priv = priv = UFO_STACKED_BACKPROJECT_TASK_GET_PRIVATE(self);
+    priv->interleave_single = NULL;
+    priv->interleave_half = NULL;
+    priv->interleave_uint = NULL;
+    priv->uninterleave_single = NULL;
+    priv->uninterleave_half = NULL;
+    priv->uninterleave_uint = NULL;
+    priv->texture_single = NULL;
+    priv->texture_half = NULL;
+    priv->texture_uint = NULL;
+    priv->n_projections = 0;
+    priv->offset = 0;
+    priv->axis_pos = -1.0;
+    priv->angle_step = -1.0;
+    priv->angle_offset = 0.0;
+    priv->real_angle_step = -1.0;
+    priv->sin_lut = NULL;
+    priv->cos_lut = NULL;
+    priv->host_sin_lut = NULL;
+    priv->host_cos_lut = NULL;
+    priv->luts_changed = TRUE;
+    priv->roi_x = priv->roi_y = 0;
+    priv->roi_width = priv->roi_height = 0;
+    priv->precision = SINGLE;
+}
\ No newline at end of file
diff --git a/src/ufo-stacked-backproject-task.h b/src/ufo-stacked-backproject-task.h
new file mode 100644
index 0000000..30f4d27
--- /dev/null
+++ b/src/ufo-stacked-backproject-task.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2011-2013 Karlsruhe Institute of Technology
+ *
+ * This file is part of Ufo.
+ *
+ * This library is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __UFO_STACKED_BACKPROJECT_TASK_H
+#define __UFO_STACKED_BACKPROJECT_TASK_H
+
+#include <ufo/ufo.h>
+
+G_BEGIN_DECLS
+
+#define UFO_TYPE_STACKED_BACKPROJECT_TASK             (ufo_stacked_backproject_task_get_type())
+#define UFO_STACKED_BACKPROJECT_TASK(obj)             (G_TYPE_CHECK_INSTANCE_CAST((obj), UFO_TYPE_STACKED_BACKPROJECT_TASK, UfoStackedBackprojectTask))
+#define UFO_IS_STACKED_BACKPROJECT_TASK(obj)          (G_TYPE_CHECK_INSTANCE_TYPE((obj), UFO_TYPE_STACKED_BACKPROJECT_TASK))
+#define UFO_STACKED_BACKPROJECT_TASK_CLASS(klass)     (G_TYPE_CHECK_CLASS_CAST((klass), UFO_TYPE_STACKED_BACKPROJECT_TASK, UfoStackedBackprojectTaskClass))
+#define UFO_IS_STACKED_BACKPROJECT_TASK_CLASS(klass)  (G_TYPE_CHECK_CLASS_TYPE((klass), UFO_TYPE_STACKED_BACKPROJECT_TASK))
+#define UFO_STACKED_BACKPROJECT_TASK_GET_CLASS(obj)   (G_TYPE_INSTANCE_GET_CLASS((obj), UFO_TYPE_STACKED_BACKPROJECT_TASK, UfoStackedBackprojectTaskClass))
+
+typedef struct _UfoStackedBackprojectTask           UfoStackedBackprojectTask;
+typedef struct _UfoStackedBackprojectTaskClass      UfoStackedBackprojectTaskClass;
+typedef struct _UfoStackedBackprojectTaskPrivate    UfoStackedBackprojectTaskPrivate;
+
+struct _UfoStackedBackprojectTask {
+    UfoTaskNode parent_instance;
+
+    UfoStackedBackprojectTaskPrivate *priv;
+};
+
+struct _UfoStackedBackprojectTaskClass {
+    UfoTaskNodeClass parent_class;
+};
+
+UfoNode  *ufo_stacked_backproject_task_new       (void);
+GType     ufo_stacked_backproject_task_get_type  (void);
+
+G_END_DECLS
+
+#endif
\ No newline at end of file