oitBufferAccessor.h

//
// Copyright 2019 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_IMAGING_HDX_OIT_BUFFER_ACCESSOR_H
#define PXR_IMAGING_HDX_OIT_BUFFER_ACCESSOR_H
 
#include "pxr/pxr.h"
#include "pxr/imaging/hdx/api.h"
#include "pxr/imaging/hdx/version.h"
 
#include "pxr/imaging/hd/task.h"
 
#include "pxr/base/gf/vec2i.h"
 
#include <memory>
 
PXR_NAMESPACE_OPEN_SCOPE
 
class Hgi;
class HdRenderIndex;
 
using HdBufferArrayRangeSharedPtr =
    std::shared_ptr<class HdBufferArrayRange>;
 
using HdStRenderPassShaderSharedPtr =
    std::shared_ptr<class HdStRenderPassShader>;
 
class HdxOitBufferAccessor {
public:
    HDX_API
    static bool IsOitEnabled();
 
    // This method helps improve the footprint of the OIT buffers by packing the
    // color, transmission and depth into smaller buffers. This follows the
    // theory in https://interplayoflight.wordpress.com/2022/06/25/order-independent-transparency-part-1/
    // This compression results in a 4x reduction in the memory footprint of the
    // OIT buffers at the cost of accuracy.
    HDX_API
    static bool IsOitPackedDepthEnabled();
 
    HDX_API
    HdxOitBufferAccessor(HdTaskContext *ctx);
 
    HDX_API
    void RequestOitBuffers();
 
    HDX_API
    void AllocateOitBuffersIfNecessary(HdRenderIndex *renderIndex);
 
    HDX_API
    bool ResizeOitBuffersIfNecessary(HdRenderIndex *renderIndex,
                                     GfVec2i const &screenSize,
                                     GfVec2i *prevScreenSize);
 
    HDX_API
    void InitializeOitBuffersIfNecessary(Hgi *hgi);
 
    HDX_API
    bool AddOitBufferBindings(const HdStRenderPassShaderSharedPtr &);
 
private:
    HdBufferArrayRangeSharedPtr const &_GetBar(const TfToken &);
 
    HdTaskContext * const _ctx;
};
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif