Add backprojection from 3d images

src/kernels/ankabackproject.cl

@@ -46,3 +46,36 @@
                 id.y * get_global_size (0) + id.x] = read_imagef (projection, sampler, pixel).x;
     }
  }
+
+
+__kernel void backproject_from_3d (global float *volume,
+                                   __read_only image3d_t projections,
+                                   const sampler_t sampler,
+                                   const float2 x_region,
+                                   const float2 y_region,
+                                   const float2 z_region,
+                                   constant float *sines,
+                                   constant float *cosines,
+                                   const float2 center,
+                                   const float sin_lamino,
+                                   const float cos_lamino)
+{
+    int3 id = (int3) (get_global_id (0), get_global_id (1), get_global_id (2));
+    int i;
+    float result = 0.0f;
+    float4 pixel;
+    float3 voxel;
+
+    voxel.x = mad((float) id.x, x_region.y, x_region.x);
+    voxel.y = mad((float) id.y, y_region.y, y_region.x);
+    voxel.z = mad((float) id.z, z_region.y, z_region.x);
+
+    for (i = 0; i < get_image_depth (projections); i++) {
+        pixel.x = voxel.x * cosines[i] + voxel.y * sines[i] + center.x;
+        pixel.y = voxel.x * cos_lamino * sines[i] - voxel.y * cos_lamino * cosines[i] + voxel.z * sin_lamino + center.y;
+        pixel.z = (float) i;
+        result += read_imagef (projections, sampler, pixel).x;
+    }
+
+    volume[id.z * get_global_size (0) * get_global_size (1) + id.y * get_global_size (0) + id.x] = result;
+}