HYDRA-747 : Filtering scene index example can have prims get unfiltered at the wrong location

lib/flowViewport/API/samples/fvpFilteringSceneIndexExample.cpp

@@ -22,12 +22,14 @@
 #include <pxr/imaging/hd/meshSchema.h>
 #include <pxr/imaging/hd/tokens.h>
 
+#include <stack>
+
 PXR_NAMESPACE_OPEN_SCOPE
 
 namespace 
 {
     //As an example, we use a filtering scene index to filter mesh primitives which have more than 10 000 vertices.
-    bool IsFiltered(const HdSceneIndexPrim& sceneIndexPrim)
+    bool ShouldBeFiltered(const HdSceneIndexPrim& sceneIndexPrim)
     {
         static bool _hideCameras        = false;
         static bool _hideSimpleLights   = false;
@@ -64,20 +66,112 @@ namespace
 }
 
 namespace FVP_NS_DEF {
+bool FilteringSceneIndexExample::IsFiltered(const SdfPath& primPath) const
+{
+    return _filteredPrims.find(primPath) != _filteredPrims.end();
+}
+
+void FilteringSceneIndexExample::UpdateFilteringStatus(const SdfPath& primPath)
+{
+    if (ShouldBeFiltered(_GetInputSceneIndex()->GetPrim(primPath))) {
+        _filteredPrims.insert(primPath);
+    } else {
+        _filteredPrims.erase(primPath);
+    }
+}
+
+FilteringSceneIndexExample::FilteringSceneIndexExample(const HdSceneIndexBaseRefPtr& inputSceneIndex)
+    : ParentClass(inputSceneIndex)
+{
+    std::stack<SdfPath> primPathsToTraverse({ SdfPath::AbsoluteRootPath() });
+    while (!primPathsToTraverse.empty()) {
+        SdfPath currPrimPath = primPathsToTraverse.top();
+        primPathsToTraverse.pop();
+        UpdateFilteringStatus(currPrimPath);
+        for (const auto& childPath : inputSceneIndex->GetChildPrimPaths(currPrimPath)) {
+            primPathsToTraverse.push(childPath);
+        }
+    }
+}
 
-//This is the function where we filter prims
 HdSceneIndexPrim FilteringSceneIndexExample::GetPrim(const SdfPath& primPath) const
 {
-    if (_GetInputSceneIndex()){
-        const HdSceneIndexPrim prim = _GetInputSceneIndex()->GetPrim(primPath);
-
-        const bool isThisPrimFiltered = IsFiltered(prim);
-        if ( ! isThisPrimFiltered){
-            return prim;//return only non filtered prims
+    return IsFiltered(primPath) ? HdSceneIndexPrim() : _GetInputSceneIndex()->GetPrim(primPath);
+}
+
+SdfPathVector FilteringSceneIndexExample::GetChildPrimPaths(const SdfPath& primPath) const {
+    if (IsFiltered(primPath)) {
+        return SdfPathVector();
+    }
+
+    SdfPathVector childPaths = _GetInputSceneIndex()->GetChildPrimPaths(primPath);
+    childPaths.erase(
+        std::remove_if(
+            childPaths.begin(),
+            childPaths.end(),
+            [this](const SdfPath& childPath) -> bool { return IsFiltered(childPath); }),
+        childPaths.end());
+    return childPaths;
+}
+
+void FilteringSceneIndexExample::_PrimsAdded(
+    const HdSceneIndexBase&                         sender,
+    const HdSceneIndexObserver::AddedPrimEntries& entries)
+{
+    HdSceneIndexObserver::AddedPrimEntries unfilteredEntries;
+    for (const auto& entry : entries) {
+        // We only want to forward the notifications for prims that don't get filtered out
+        UpdateFilteringStatus(entry.primPath);
+        if (!IsFiltered(entry.primPath)) {
+            unfilteredEntries.push_back(entry);
         }
     }
+    _SendPrimsAdded(unfilteredEntries);
+}
 
-    return HdSceneIndexPrim();
+void FilteringSceneIndexExample::_PrimsRemoved(
+    const HdSceneIndexBase&                       sender,
+    const HdSceneIndexObserver::RemovedPrimEntries& entries)
+{
+    for (const auto& entry : entries) {
+        // We don't need to update or check the filtering status, since the prim is getting removed either way
+        _filteredPrims.erase(entry.primPath);
+    }
+    _SendPrimsRemoved(entries);
+}
+
+void FilteringSceneIndexExample::_PrimsDirtied(
+    const HdSceneIndexBase&                         sender,
+    const HdSceneIndexObserver::DirtiedPrimEntries& entries)
+{
+    // There are three potential scenarios here for a given prim :
+    // 1. Its filtering status did NOT change -> forward the PrimsDirtied notification as-is
+    // 2. Its filtering status DID change :
+    //    2a. If the prim was previously filtered -> it is now unfiltered, so send a PrimsAdded notification
+    //    2b. If the prim was previously unfiltered -> it is now filtered, so send a PrimsRemoved notification
+    HdSceneIndexObserver::AddedPrimEntries   newlyUnfilteredEntries;
+    HdSceneIndexObserver::RemovedPrimEntries newlyFilteredEntries;
+    HdSceneIndexObserver::DirtiedPrimEntries dirtiedEntries;
+    for (const auto& entry : entries) {
+        bool wasPreviouslyFiltered = IsFiltered(entry.primPath);
+        UpdateFilteringStatus(entry.primPath);
+        if (wasPreviouslyFiltered == IsFiltered(entry.primPath)) {
+            // Filtering status did not change, forward notification as-is
+            dirtiedEntries.push_back(entry);
+        }
+        else {
+            // Filtering status changed, send a different notification instead
+            if (wasPreviouslyFiltered) {
+                    newlyUnfilteredEntries.emplace_back(
+                        entry.primPath, _GetInputSceneIndex()->GetPrim(entry.primPath).primType);
+            } else {
+                    newlyFilteredEntries.emplace_back(entry.primPath);
+            }
+        }
+    }
+    _SendPrimsAdded(newlyUnfilteredEntries);
+    _SendPrimsRemoved(newlyFilteredEntries);
+    _SendPrimsDirtied(dirtiedEntries);
 }
 
 }//end of namespace FVP_NS_DEF

lib/flowViewport/API/samples/fvpFilteringSceneIndexExample.h

@@ -46,41 +46,32 @@ class FilteringSceneIndexExample : public HdSingleInputFilteringSceneIndexBase
     }
 
     // From HdSceneIndexBase
-    HdSceneIndexPrim GetPrim(const SdfPath& primPath) const override;//Is the useful function where we do filtering
+    HdSceneIndexPrim GetPrim(const SdfPath& primPath) const override;
 
-    SdfPathVector GetChildPrimPaths(const SdfPath& primPath) const override{//We leave this function with no filtering for simplicity
-        if (_GetInputSceneIndex()){
-            return _GetInputSceneIndex()->GetChildPrimPaths(primPath);
-        }
-
-        return {};
-    }
+    SdfPathVector GetChildPrimPaths(const SdfPath& primPath) const override;
 
     ~FilteringSceneIndexExample() override = default;
 
 protected:
-    FilteringSceneIndexExample(const HdSceneIndexBaseRefPtr& inputSceneIndex) : ParentClass(inputSceneIndex) {}
+    FilteringSceneIndexExample(const HdSceneIndexBaseRefPtr& inputSceneIndex);
 
     void _PrimsAdded(
         const HdSceneIndexBase&                       sender,
-        const HdSceneIndexObserver::AddedPrimEntries& entries) override final
-    {
-        _SendPrimsAdded(entries);
-    }
+        const HdSceneIndexObserver::AddedPrimEntries& entries) override;
 
     void _PrimsRemoved(
         const HdSceneIndexBase&                         sender,
-        const HdSceneIndexObserver::RemovedPrimEntries& entries) override 
-    {
-        _SendPrimsRemoved(entries);
-    }
+        const HdSceneIndexObserver::RemovedPrimEntries& entries) override;
 
     void _PrimsDirtied(
         const HdSceneIndexBase&                         sender,
-        const HdSceneIndexObserver::DirtiedPrimEntries& entries) override 
-        {
-            _SendPrimsDirtied(entries);
-        }
+        const HdSceneIndexObserver::DirtiedPrimEntries& entries) override;
+
+    bool IsFiltered(const SdfPath& primPath) const;
+
+    void UpdateFilteringStatus(const SdfPath& primPath);
+
+    SdfPathSet _filteredPrims;
 };
 
 }//end of namespace FVP_NS_DEF