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Hgi Class Referenceabstract

#include <hgi.h>

+ Inheritance diagram for Hgi:

Public Member Functions

HGI_API Hgi ()
 
virtual HGI_API ~Hgi ()
 
HGI_API void SubmitCmds (HgiCmds *cmds)
 
virtual HGI_API
HgiGraphicsCmdsUniquePtr 
CreateGraphicsCmds (HgiGraphicsCmdsDesc const &desc)=0
 
virtual HGI_API
HgiBlitCmdsUniquePtr 
CreateBlitCmds ()=0
 
virtual HGI_API
HgiComputeCmdsUniquePtr 
CreateComputeCmds ()=0
 
virtual HGI_API HgiTextureHandle CreateTexture (HgiTextureDesc const &desc)=0
 
virtual HGI_API void DestroyTexture (HgiTextureHandle *texHandle)=0
 
virtual HGI_API HgiSamplerHandle CreateSampler (HgiSamplerDesc const &desc)=0
 
virtual HGI_API void DestroySampler (HgiSamplerHandle *smpHandle)=0
 
virtual HGI_API HgiBufferHandle CreateBuffer (HgiBufferDesc const &desc)=0
 
virtual HGI_API void DestroyBuffer (HgiBufferHandle *bufHandle)=0
 
virtual HGI_API
HgiShaderFunctionHandle 
CreateShaderFunction (HgiShaderFunctionDesc const &desc)=0
 
virtual HGI_API void DestroyShaderFunction (HgiShaderFunctionHandle *shaderFunctionHandle)=0
 
virtual HGI_API
HgiShaderProgramHandle 
CreateShaderProgram (HgiShaderProgramDesc const &desc)=0
 
virtual HGI_API void DestroyShaderProgram (HgiShaderProgramHandle *shaderProgramHandle)=0
 
virtual HGI_API
HgiResourceBindingsHandle 
CreateResourceBindings (HgiResourceBindingsDesc const &desc)=0
 
virtual HGI_API void DestroyResourceBindings (HgiResourceBindingsHandle *resHandle)=0
 
virtual HGI_API
HgiGraphicsPipelineHandle 
CreateGraphicsPipeline (HgiGraphicsPipelineDesc const &pipeDesc)=0
 
virtual HGI_API void DestroyGraphicsPipeline (HgiGraphicsPipelineHandle *pipeHandle)=0
 
virtual HGI_API
HgiComputePipelineHandle 
CreateComputePipeline (HgiComputePipelineDesc const &pipeDesc)=0
 
virtual HGI_API void DestroyComputePipeline (HgiComputePipelineHandle *pipeHandle)=0
 
virtual HGI_API TfToken constGetAPIName () const =0
 
virtual HGI_API void StartFrame ()=0
 
virtual HGI_API void EndFrame ()=0
 

Static Public Member Functions

static HGI_API HgiGetPlatformDefaultHgi ()
 *** DEPRECATED *** Please use: CreatePlatformDefaultHgi More...
 
static HGI_API HgiUniquePtr CreatePlatformDefaultHgi ()
 

Protected Member Functions

HGI_API uint64_t GetUniqueId ()
 
virtual HGI_API bool _SubmitCmds (HgiCmds *cmds)
 

Detailed Description

Hydra Graphics Interface. Hgi is used to communicate with one or more physical gpu devices.

Hgi provides API to create/destroy resources that a gpu device owns. The lifetime of resources is not managed by Hgi, so it is up to the caller to destroy resources and ensure those resources are no longer used.

Commands are recorded in 'HgiCmds' objects and submitted via Hgi.

Thread-safety:

Modern graphics APIs like Metal and Vulkan are designed with multi-threading in mind. We want to try and take advantage of this where possible. However we also wish to continue to support OpenGL for the time being.

In an application where OpenGL is involved, when we say "main thread" we mean the thread on which the gl-context is bound.

Each Hgi backend should at minimum support the following:

  • Single threaded Hgi::SubmitCmds on main thread.
  • Single threaded Hgi::Resource Create*** / Destroy*** on main thread.
  • Multi threaded recording of commands in Hgi***Cmds objects.
  • A Hgi***Cmds object should be creatable on the main thread, recorded into with one secondary thread (only one thread may use a Cmds object) and submitted via the main thread.

Each Hgi backend is additionally encouraged to support:

  • Multi threaded support for resource creation and destruction.

We currently do not rely on these additional multi-threading features in Hydra / Storm where we still wish to run OpenGL. In Hydra we make sure to use the main-thread for resource creation and command submission. One day we may wish to switch this to be multi-threaded so new Hgi backends are encouraged to support it.

Pseudo code what should minimally be supported:

vector<HgiGraphicsCmds> cmds

for num_threads
    cmds.push_back( Hgi->CreateGraphicsCmds() )

parallel_for i to num_threads
    cmds[i]->SetViewport()
    cmds[i]->Draw()

for i to num_threads
    hgi->SubmitCmds( cmds[i] )

Definition at line 106 of file hgi.h.

Constructor & Destructor Documentation

HGI_API Hgi::Hgi ( )
virtual HGI_API Hgi::~Hgi ( )
virtual

Member Function Documentation

virtual HGI_API bool Hgi::_SubmitCmds ( HgiCmds cmds)
protectedvirtual

Reimplemented in HgiGL.

virtual HGI_API HgiBlitCmdsUniquePtr Hgi::CreateBlitCmds ( )
pure virtual

Returns a BlitCmds object (for temporary use) that is ready to execute resource copy commands. BlitCmds is a lightweight object that should be re-acquired each frame (don't hold onto it after EndEncoding). Thread safety: Each Hgi backend must ensure that a Cmds object can be created on the main thread, recorded into (exclusively) by one secondary thread and be submitted on the main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiBufferHandle Hgi::CreateBuffer ( HgiBufferDesc const desc)
pure virtual

Create a buffer in rendering backend. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiComputeCmdsUniquePtr Hgi::CreateComputeCmds ( )
pure virtual

Returns a ComputeCmds object (for temporary use) that is ready to record dispatch commands. ComputeCmds is a lightweight object that should be re-acquired each frame (don't hold onto it after EndEncoding). Thread safety: Each Hgi backend must ensure that a Cmds object can be created on the main thread, recorded into (exclusively) by one secondary thread and be submitted on the main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiComputePipelineHandle Hgi::CreateComputePipeline ( HgiComputePipelineDesc const pipeDesc)
pure virtual

Create a new compute pipeline state object. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiGraphicsCmdsUniquePtr Hgi::CreateGraphicsCmds ( HgiGraphicsCmdsDesc const desc)
pure virtual

Returns a GraphicsCmds object (for temporary use) that is ready to record draw commands. GraphicsCmds is a lightweight object that should be re-acquired each frame (don't hold onto it after EndEncoding). Thread safety: Each Hgi backend must ensure that a Cmds object can be created on the main thread, recorded into (exclusively) by one secondary thread and be submitted on the main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiGraphicsPipelineHandle Hgi::CreateGraphicsPipeline ( HgiGraphicsPipelineDesc const pipeDesc)
pure virtual

Create a new graphics pipeline state object. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

static HGI_API HgiUniquePtr Hgi::CreatePlatformDefaultHgi ( )
static

Helper function to return a Hgi object for the current platform. For example on Linux this may return HgiGL while on macOS HgiMetal. Caller, usually the application, owns the lifetime of the Hgi object and the object is destroyed when the caller drops the unique ptr. Thread safety: Not thread safe.

virtual HGI_API HgiResourceBindingsHandle Hgi::CreateResourceBindings ( HgiResourceBindingsDesc const desc)
pure virtual

Create a new resource binding object. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiSamplerHandle Hgi::CreateSampler ( HgiSamplerDesc const desc)
pure virtual

Create a sampler in rendering backend. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiShaderFunctionHandle Hgi::CreateShaderFunction ( HgiShaderFunctionDesc const desc)
pure virtual

Create a new shader function. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiShaderProgramHandle Hgi::CreateShaderProgram ( HgiShaderProgramDesc const desc)
pure virtual

Create a new shader program. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API HgiTextureHandle Hgi::CreateTexture ( HgiTextureDesc const desc)
pure virtual

Create a texture in rendering backend. Thread safety: Creation must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroyBuffer ( HgiBufferHandle bufHandle)
pure virtual

Destroy a buffer in rendering backend. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroyComputePipeline ( HgiComputePipelineHandle pipeHandle)
pure virtual

Destroy a compute pipeline state object. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroyGraphicsPipeline ( HgiGraphicsPipelineHandle pipeHandle)
pure virtual

Destroy a graphics pipeline state object. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroyResourceBindings ( HgiResourceBindingsHandle resHandle)
pure virtual

Destroy a resource binding object. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroySampler ( HgiSamplerHandle smpHandle)
pure virtual

Destroy a sampler in rendering backend. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroyShaderFunction ( HgiShaderFunctionHandle shaderFunctionHandle)
pure virtual

Destroy a shader function. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroyShaderProgram ( HgiShaderProgramHandle shaderProgramHandle)
pure virtual

Destroy a shader program. Note that this does NOT automatically destroy the shader functions in the program since shader functions may be used by more than one program. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::DestroyTexture ( HgiTextureHandle texHandle)
pure virtual

Destroy a texture in rendering backend. Thread safety: Destruction must happen on main thread. See notes above.

Implemented in HgiGL.

virtual HGI_API void Hgi::EndFrame ( )
pure virtual

Optionally called at the end of a rendering frame. Please read the comments in StartFrame. Thread safety: Not thread safe. Should be called on the main thread.

Implemented in HgiGL.

virtual HGI_API TfToken const& Hgi::GetAPIName ( ) const
pure virtual

Return the name of the api (e.g. "OpenGL"). Thread safety: This call is thread safe.

Implemented in HgiGL.

static HGI_API Hgi* Hgi::GetPlatformDefaultHgi ( )
static

*** DEPRECATED *** Please use: CreatePlatformDefaultHgi

HGI_API uint64_t Hgi::GetUniqueId ( )
protected
virtual HGI_API void Hgi::StartFrame ( )
pure virtual

Optionally called by client app at the start of a new rendering frame. We can't rely on StartFrame for anything important, because it is up to the external client to (optionally) call this and they may never do. Hydra doesn't have a clearly defined start or end frame. This can be helpful to insert GPU frame debug markers. Thread safety: Not thread safe. Should be called on the main thread.

Implemented in HgiGL.

HGI_API void Hgi::SubmitCmds ( HgiCmds cmds)

Submit one HgiCmds objects. Once the cmds object is submitted it cannot be re-used to record cmds. A call to SubmitCmds would usually result in the hgi backend submitting the cmd buffers of the cmds object(s) to the device queue. Derived classes can override _SubmitCmds to customize submission. Thread safety: This call is not thread-safe. Submission must happen on the main thread so we can continue to support the OpenGL platform. See notes above.


The documentation for this class was generated from the following file: