feat(compression): add descendant indices to topology metadata

includes/acl/compression/impl/topology_metadata.h

@@ -61,6 +61,13 @@ namespace acl
 			// Number of leaves beneath this transform (and present in the list above)
 			uint32_t num_leaves = 0;
 
+			// A list of descendant transform indices beneath this transform (points into 'aggregate_descendant_indices' in owner clip_topology_t)
+			// Descendants are sorted parent first
+			const uint32_t* descendants = nullptr;
+
+			// Number of descendants beneath this transform (and present in the list above)
+			uint32_t num_descendants = 0;
+
 			// Whether or not this transform is a leaf
 			bool is_leaf() const { return num_children == 0; }
 
@@ -72,6 +79,9 @@ namespace acl
 
 			// Returns a transform index iterator over the list of leaves
 			const_array_iterator<uint32_t> leaves_iterator() const;
+
+			// Returns a transform index iterator over the list of descendants
+			const_array_iterator<uint32_t> descendants_iterator() const;
 		};
 
 		// Topology metadata for a clip
@@ -118,6 +128,13 @@ namespace acl
 			// Size of global list of leaf indices
 			uint32_t num_aggregate_leaf_indices			= 0;
 
+			// Global list of descendant indices
+			// Each transform contains a pointer into this list
+			uint32_t* aggregate_descendant_indices		= nullptr;
+
+			// Size of global list of descendant indices
+			uint32_t num_aggregate_descendant_indices	= 0;
+
 			// The allocator used for the topology metadata, never null if initialized
 			iallocator* allocator						= nullptr;
 

includes/acl/compression/impl/topology_metadata.impl.h

@@ -49,6 +49,11 @@ namespace acl
 			return make_iterator(leaves, num_leaves);
 		}
 
+		inline const_array_iterator<uint32_t> transform_topology_t::descendants_iterator() const
+		{
+			return make_iterator(descendants, num_descendants);
+		}
+
 		inline const_array_iterator<uint32_t> clip_topology_t::roots_first_iterator() const
 		{
 			return make_iterator(static_cast<const uint32_t*>(transform_indices_sorted_parent_first), num_transforms);
@@ -73,6 +78,7 @@ namespace acl
 			deallocate_type_array(*allocator, transform_indices_sorted_parent_first, num_transforms);
 			deallocate_type_array(*allocator, aggregate_children_indices, num_aggregate_children_indices);
 			deallocate_type_array(*allocator, aggregate_leaf_indices, num_aggregate_leaf_indices);
+			deallocate_type_array(*allocator, aggregate_descendant_indices, num_aggregate_descendant_indices);
 		}
 
 		inline void build_clip_topology(iallocator& allocator, const track_array_qvvf& track_list, clip_topology_t& out_topology)
@@ -221,6 +227,52 @@ namespace acl
 				std::sort(transform_indices_sorted_parent_first, transform_indices_sorted_parent_first + num_transforms, sort_predicate);
 			}
 
+			uint32_t num_aggregate_descendant_indices = 0;
+			uint32_t* aggregate_descendant_indices = nullptr;
+			{
+				// Find our descendants
+				for (uint32_t transform_index : make_iterator(transform_indices_sorted_parent_first, num_transforms))
+				{
+					uint32_t cursor_index = topology_per_transform[transform_index].parent_index;
+					while (cursor_index != k_invalid_track_index)
+					{
+						topology_per_transform[cursor_index].num_descendants++;
+						num_aggregate_descendant_indices++;
+
+						cursor_index = topology_per_transform[cursor_index].parent_index;
+					}
+				}
+
+				// Allocate the list of descendant indices and partition it among the transforms
+				aggregate_descendant_indices = allocate_type_array<uint32_t>(allocator, num_aggregate_descendant_indices);
+				uint32_t num_assigned_descendant_indices = 0;
+
+				for (uint32_t transform_index = 0; transform_index < num_transforms; ++transform_index)
+				{
+					topology_per_transform[transform_index].descendants = aggregate_descendant_indices + num_assigned_descendant_indices;
+					num_assigned_descendant_indices += topology_per_transform[transform_index].num_descendants;
+
+					// Reset the descendant count, we'll use it to write our indices below and repopulate it
+					topology_per_transform[transform_index].num_descendants = 0;
+				}
+
+				// Populate the list of descendants
+				for (uint32_t transform_index : make_iterator(transform_indices_sorted_parent_first, num_transforms))
+				{
+					uint32_t cursor_index = topology_per_transform[transform_index].parent_index;
+					while (cursor_index != k_invalid_track_index)
+					{
+						const ptrdiff_t indices_offset = topology_per_transform[cursor_index].descendants - aggregate_descendant_indices;
+						uint32_t* cursor_descendants = aggregate_descendant_indices + indices_offset;
+
+						cursor_descendants[topology_per_transform[cursor_index].num_descendants] = transform_index;
+						topology_per_transform[cursor_index].num_descendants++;
+
+						cursor_index = topology_per_transform[cursor_index].parent_index;
+					}
+				}
+			}
+
 			uint32_t num_max_leaves_per_transform = 0;
 			for (uint32_t root_index = 0; root_index < num_root_transforms; ++root_index)
 			{
@@ -252,6 +304,8 @@ namespace acl
 			out_topology.num_aggregate_children_indices = num_children_transforms;
 			out_topology.aggregate_leaf_indices = clip_leaf_indices;
 			out_topology.num_aggregate_leaf_indices = num_leaf_transform_indices;
+			out_topology.aggregate_descendant_indices = aggregate_descendant_indices;
+			out_topology.num_aggregate_descendant_indices = num_aggregate_descendant_indices;
 			out_topology.allocator = &allocator;
 		}
 	}

tools/vs_visualizers/acl.natvis

@@ -180,8 +180,10 @@
   </Type>
 
   <Type Name="acl::acl_impl::transform_topology_t">
-    <DisplayString Condition="num_children == 0">parent={parent_index}, num_children={num_children} (leaf)</DisplayString>
-    <DisplayString>parent={parent_index}, num_children={num_children}</DisplayString>
+    <DisplayString Condition="num_children == 0 &amp;&amp; parent_index == k_invalid_track_index">(root + leaf)</DisplayString>
+    <DisplayString Condition="num_children == 0">parent={parent_index} (leaf)</DisplayString>
+    <DisplayString Condition="parent_index == k_invalid_track_index">num_children={num_children}, num_descendants={num_descendants} (root)</DisplayString>
+    <DisplayString>parent={parent_index}, num_children={num_children}, num_descendants={num_descendants}</DisplayString>
     <Expand>
       <Item Name="parent_index">parent_index</Item>
       <Item Name="depth_from_root">depth_from_root</Item>
@@ -205,6 +207,15 @@
           </ArrayItems>
         </Expand>
       </Synthetic>
+      <Synthetic Name="descendants">
+        <DisplayString>count={num_descendants}</DisplayString>
+        <Expand>
+          <ArrayItems>
+            <Size>num_descendants</Size>
+            <ValuePointer>descendants</ValuePointer>
+          </ArrayItems>
+        </Expand>
+      </Synthetic>
     </Expand>
   </Type>