renderBufferPool.h

//
// Copyright 2025 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_IMAGING_HD_ST_RENDER_BUFFER_POOL_H
#define PXR_IMAGING_HD_ST_RENDER_BUFFER_POOL_H
 
#include "pxr/pxr.h"
#include "pxr/base/gf/vec3i.h"
#include "pxr/imaging/hdSt/api.h"
#include "pxr/imaging/hdSt/renderBuffer.h"
#include "pxr/imaging/hgi/hgi.h"
#include "pxr/imaging/hgi/enums.h"
#include "pxr/imaging/hgi/texture.h"
 
#include <deque>
#include <map>
#include <unordered_map>
 
PXR_NAMESPACE_OPEN_SCOPE
 
class HdStRenderBufferPool;
 
class HdStPooledRenderBuffer final
{
public:
    HdStPooledRenderBuffer(
        std::shared_ptr<HdStRenderBuffer> buffer,
        HdStRenderBufferPool* pool,
        const SdfPath& graphPath,
        bool isDepth,
        uint16_t idx);
    ~HdStPooledRenderBuffer();
 
    HdStRenderBuffer* GetBuffer() const { return _buffer.get(); }
private:
    std::shared_ptr<HdStRenderBuffer> _buffer;
    HdStRenderBufferPool* _pool;
    const SdfPath _graphPath;
    bool _isDepth;
    uint16_t _idx;
 
    HdStPooledRenderBuffer & operator=(const HdStPooledRenderBuffer&) = delete;
    HdStPooledRenderBuffer(const HdStPooledRenderBuffer&) = delete;
};
 
using HdStPooledRenderBufferUniquePtr = std::unique_ptr<HdStPooledRenderBuffer>;
 
class HdStRenderBufferPool
{
public:
    // Allocate a RenderBuffer for usage during the current render graph
    [[nodiscard]]
    HDST_API
    HdStPooledRenderBufferUniquePtr Allocate(
        HdStResourceRegistry* registry,
        const SdfPath& graphPath,
        HdFormat fmt,
        GfVec2i dims,
        bool multiSampled,
        bool depth);
 
    HDST_API
    void Free(
        HdFormat fmt,
        GfVec2i dims,
        bool multiSampled,
        bool depth,
        const SdfPath& graphPath,
        uint16_t idx);
 
    // Frees allocations that are no longer in use by any render graphs
    HDST_API
    void Commit();
private:
    struct _PooledRenderBufferDesc
    {
        HdFormat fmt : 6;
        bool multiSampled : 1;
        bool depth : 1;
        GfVec2i dims;
        bool operator==(const _PooledRenderBufferDesc &other) const
        {
            return fmt == other.fmt &&
                dims == other.dims &&
                multiSampled == other.multiSampled &&
                depth == other.depth;
        }
        struct HashFunctor
        {
            size_t operator()(_PooledRenderBufferDesc const& desc) const
            {
                return ((desc.multiSampled | (desc.depth << 2)
                    | (desc.fmt << 3))
                    ^ (desc.dims[0] & 0xFFFF))
                    | ((size_t)(desc.dims[1] & 0xFFFF) << 32);
            }
        };
    };
 
    using _HdStRenderBufferVec =
        std::vector<std::shared_ptr<HdStRenderBuffer>>;
 
    class _AllocationTracker
    {
    public:
        uint16_t Allocate();
        void Free(uint16_t index);
    private:
        uint16_t max = 0;
        std::deque<uint16_t> freeList;
    };
 
    struct _HdStRenderBufferPoolEntry
    {
        std::map<const SdfPath, _AllocationTracker> allocs;
        _HdStRenderBufferVec buffers;
    };
    
    std::unordered_map<_PooledRenderBufferDesc,
        _HdStRenderBufferPoolEntry,
        _PooledRenderBufferDesc::HashFunctor> _pooledRenderBuffers;
};
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif