mergingSceneIndex.h

//
// Copyright 2021 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_IMAGING_HD_MERGING_SCENE_H
#define PXR_IMAGING_HD_MERGING_SCENE_H
 
#include "pxr/pxr.h"
#include "pxr/imaging/hd/filteringSceneIndex.h"
#include "pxr/usd/sdf/pathTable.h"
#include "pxr/base/tf/smallVector.h"
 
#include <limits>
 
PXR_NAMESPACE_OPEN_SCOPE
 
class HdMergingSceneIndex;
TF_DECLARE_REF_PTRS(HdMergingSceneIndex);
 
class HdMergingSceneIndex : public HdFilteringSceneIndexBase
{
public:
 
    static HdMergingSceneIndexRefPtr New() {
        return TfCreateRefPtr(new HdMergingSceneIndex);
    }
 
    struct InputScene
    {
        HdSceneIndexBaseRefPtr scene;
        SdfPath activeInputSceneRoot = SdfPath::AbsoluteRootPath();
        size_t pos = std::numeric_limits<size_t>::max();
    };
 
    HD_API
    void InsertInputScenes(
        const std::vector<InputScene> &inputScenes);
 
    HD_API
    void RemoveInputScenes(
        const std::vector<HdSceneIndexBaseRefPtr> &sceneIndices);
 
    HD_API
    void AddInputScene(
        const HdSceneIndexBaseRefPtr &inputScene,
        const SdfPath &activeInputSceneRoot);
 
    HD_API
    void InsertInputScene(
        size_t pos,
        const HdSceneIndexBaseRefPtr &inputScene,
        const SdfPath &activeInputSceneRoot);
 
    HD_API
    void RemoveInputScene(const HdSceneIndexBaseRefPtr &sceneIndex);
 
    HD_API
    std::vector<HdSceneIndexBaseRefPtr> GetInputScenes() const override;
 
    // satisfying HdSceneIndexBase
    HD_API
    HdSceneIndexPrim GetPrim(const SdfPath &primPath) const override;
 
    HD_API
    SdfPathVector GetChildPrimPaths(const SdfPath &primPath) const override;
 
protected:
    HD_API
    HdMergingSceneIndex();
 
private:
 
    void _PrimsAdded(
        const HdSceneIndexBase &sender,
        const HdSceneIndexObserver::AddedPrimEntries &entries);
 
    void _PrimsRemoved(
        const HdSceneIndexBase &sender,
        const HdSceneIndexObserver::RemovedPrimEntries &entries);
 
    void _PrimsDirtied(
        const HdSceneIndexBase &sender,
        const HdSceneIndexObserver::DirtiedPrimEntries &entries);
 
    friend class _Observer;
 
    // Rebuild _inputsPathTable from the current contents of _inputs.
    void _RebuildInputsPathTable();
 
    // Add strict prefixes of activeInputSceneRoot's.
    //
    // If adding a scene inde at, e.g., /A/B/C, make
    // AddedPrimEntries for /A and /A/B.
    void _AddStrictPrefixesOfSceneRoots(
        const std::vector<InputScene> &inputScenes,
        HdSceneIndexObserver::AddedPrimEntries * addedEntries);
 
    bool _HasPrim(const SdfPath &path);
 
    class _Observer : public HdSceneIndexObserver
    {
    public:
        _Observer(HdMergingSceneIndex *owner)
        : _owner(owner) {}
 
        void PrimsAdded(
            const HdSceneIndexBase &sender,
            const AddedPrimEntries &entries) override;
 
        void PrimsRemoved(
            const HdSceneIndexBase &sender,
            const RemovedPrimEntries &entries) override;
 
        void PrimsDirtied(
            const HdSceneIndexBase &sender,
            const DirtiedPrimEntries &entries) override;
 
        void PrimsRenamed(
            const HdSceneIndexBase &sender,
            const RenamedPrimEntries &entries) override;
 
    private:
        HdMergingSceneIndex *_owner;
    };
 
    _Observer _observer;
 
    struct _InputEntry
    {
        HdSceneIndexBaseRefPtr sceneIndex;
        SdfPath sceneRoot;
 
        _InputEntry(const HdSceneIndexBaseRefPtr &sceneIndex,
                const SdfPath &sceneRoot)
        : sceneIndex(sceneIndex)
        , sceneRoot(sceneRoot)
        {
        }
    };
 
    // We observe that most merging scene indexes have few inputs, such as 2.
    // However, in the case of merging USD native instance prototypes in
    // UsdImaging, we may have hundreds of inputs with non-overlapping
    // sceneRoots .  To avoid an O(N) scan over all inputs when N grows
    // large, we use an SdfPathTable to store ordered sub-list of inputs
    // that pertain to an input prim path or input ancestor path.
    using _InputEntries = TfSmallVector<_InputEntry, 4>;
    using _InputEntriesByPathTable = SdfPathTable<_InputEntries>;
 
    // Look up the input entries potentially relevant to the given path.
    const _InputEntries &_GetInputEntriesByPath(SdfPath const& path) const;
 
    _InputEntries _inputs;
    _InputEntriesByPathTable _inputsPathTable;
 
};
 
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif //PXR_IMAGING_HD_MERGING_SCENE_H