Compositor: Unify Defocus node between CPU and GPU

This patch unifies the Defocus node between the CPU and GPU compositors.
Both nodes now use a variable sized bokeh kernel which is always odd
sized for a center pixel guarantee. Further the CPU implementation now
properly handles half pixel offsets when doing interpolation, and always
sets the threshold to zero similar to the GPU implementation.

source/blender/compositor/nodes/COM_DefocusNode.cc

@@ -91,6 +91,7 @@ void DefocusNode::convert_to_operations(NodeConverter &converter,
 
   BokehImageOperation *bokeh = new BokehImageOperation();
   bokeh->set_data(bokehdata);
+  bokeh->set_resolution(math::ceil(data->maxblur) * 2 + 1);
   bokeh->delete_data_on_finish();
   converter.add_operation(bokeh);
 
@@ -101,7 +102,7 @@ void DefocusNode::convert_to_operations(NodeConverter &converter,
   VariableSizeBokehBlurOperation *operation = new VariableSizeBokehBlurOperation();
   operation->set_quality(eCompositorQuality::High);
   operation->set_max_blur(data->maxblur);
-  operation->set_threshold(data->bthresh);
+  operation->set_threshold(0.0f);
   converter.add_operation(operation);
 
   converter.add_link(bokeh->get_output_socket(), operation->get_input_socket(1));

source/blender/compositor/operations/COM_VariableSizeBokehBlurOperation.cc

@@ -87,7 +87,6 @@ void VariableSizeBokehBlurOperation::update_memory_buffer_partial(MemoryBuffer *
   const float base_size = do_size_scale_ ? (max_dim / 100.0f) : 1.0f;
   const float maximum_size = size_buffer->get_max_value();
   const int search_radius = math::clamp(int(maximum_size * base_size), 0, max_blur_);
-  const int2 bokeh_size = int2(bokeh_buffer->get_width(), bokeh_buffer->get_height());
 
   BuffersIterator<float> it = output->iterate_with({}, area);
   for (; !it.is_end(); ++it) {
@@ -115,8 +114,8 @@ void VariableSizeBokehBlurOperation::update_memory_buffer_partial(MemoryBuffer *
           }
 
           const float2 normalized_texel = (float2(xi, yi) + size + 0.5f) / (size * 2.0f + 1.0f);
-          const float2 weight_texel = (1.0f - normalized_texel) * float2(bokeh_size - 1);
-          const float4 weight = bokeh_buffer->get_elem(int(weight_texel.x), int(weight_texel.y));
+          const float2 weight_texel = 1.0f - normalized_texel;
+          const float4 weight = bokeh_buffer->texture_bilinear_extend(weight_texel);
           const float4 color = input_buffer->get_elem_clamped(it.x + xi, it.y + yi);
           accumulated_color += color * weight;
           accumulated_weight += weight;

source/blender/nodes/composite/nodes/node_composite_defocus.cc

@@ -115,12 +115,12 @@ class DefocusOperation : public NodeOperation {
 
     Result radius = compute_defocus_radius();
 
-    const int maximum_defocus_radius = compute_maximum_defocus_radius();
+    const int maximum_defocus_radius = math::ceil(compute_maximum_defocus_radius());
 
     /* The special zero value indicate a circle, in which case, the roundness should be set to
      * 1, and the number of sides can be anything and is arbitrarily set to 3. */
     const bool is_circle = node_storage(bnode()).bktype == 0;
-    const int2 kernel_size = int2(maximum_defocus_radius * 2);
+    const int2 kernel_size = int2(maximum_defocus_radius * 2 + 1);
     const int sides = is_circle ? 3 : node_storage(bnode()).bktype;
     const float rotation = node_storage(bnode()).rotation;
     const float roundness = is_circle ? 1.0f : 0.0f;