Diligent Core

This module implements Diligent Engine's core functionality: Direct3D11, Direct3D12, OpenGL, OpenGLES, and Vulkan rendering backends as well as basic platform-specific utilities. It is self-contained and can be built by its own. The module's cmake script defines a number of variables that are required to generate build files for other modules, so it must always be handled first.

Platform	Build Status
Win32
Universal Windows
Linux
MacOS
iOS

Clonning the Repository
API Basics
Low-level API interoperability
Repository structure
Contributing
License
References
Release History

Clonning the Repository

To get the repository and all submodules, use the following command:

git clone --recursive https://github.com/DiligentGraphics/DiligentCore.git

To build the module, see build instructions in the master repository.

API Basics

Initializing the Engine

Before you can use any functionality provided by the engine, you need to create a render device, an immediate context and a swap chain.

Win32

On Win32 platform, you can create OpenGL, Direct3D11, Direct3D12 or Vulkan device as shown below:

void InitializeDiligentEngine(HWND NativeWindowHandle)
{
    SwapChainDesc SCDesc;
    SCDesc.SamplesCount = 1;
    switch (m_DeviceType)
    {
        case DeviceType::D3D11:
        {
            EngineD3D11CreateInfo EngineCI;
#if ENGINE_DLL
            GetEngineFactoryD3D11Type GetEngineFactoryD3D11 = nullptr;
            // Load the dll and import GetEngineFactoryD3D11() function
            LoadGraphicsEngineD3D11(GetEngineFactoryD3D11);
#endif
            auto* pFactoryD3D11 = GetEngineFactoryD3D11();
            pFactoryD3D11->CreateDeviceAndContextsD3D11(EngineCI, &m_pDevice, &m_pImmediateContext);
            pFactoryD3D11->CreateSwapChainD3D11(m_pDevice, m_pImmediateContext,
                                    SCDesc, NativeWindowHandle, &m_pSwapChain);
        }
        break;

        case DeviceType::D3D12:
        {
#if ENGINE_DLL
            GetEngineFactoryD3D12Type GetEngineFactoryD3D12 = nullptr;
            // Load the dll and import GetEngineFactoryD3D12() function
            LoadGraphicsEngineD3D12(GetEngineFactoryD3D12);
#endif
            EngineD3D12CreateInfo EngineCI;
            auto* pFactoryD3D12 = GetEngineFactoryD3D12();
            pFactoryD3D12->CreateDeviceAndContextsD3D12(EngineCI, &m_pDevice, &m_pImmediateContext);
            pFactoryD3D12->CreateSwapChainD3D12(m_pDevice, m_pImmediateContext,
                                    SCDesc, NativeWindowHandle, &m_pSwapChain);
        }
        break;

    case DeviceType::OpenGL:
    {

#if ENGINE_DLL
        // Declare function pointer
        GetEngineFactoryOpenGLType GetEngineFactoryOpenGL = nullptr;
        // Load the dll and import GetEngineFactoryOpenGL() function
        LoadGraphicsEngineOpenGL(GetEngineFactoryOpenGL);
#endif
        auto* pFactoryOpenGL = GetEngineFactoryOpenGL();
        EngineGLCreateInfo EngineCI;
        EngineCI.Window.hWnd = NativeWindowHandle;
        pFactoryOpenGL->CreateDeviceAndSwapChainGL(
            EngineCI, &m_pDevice, &m_pImmediateContext, SCDesc, &m_pSwapChain);
    }
    break;

    case DeviceType::Vulkan:
    {
#if ENGINE_DLL
        GetEngineFactoryVkType GetEngineFactoryVk = nullptr;
        // Load the dll and import GetEngineFactoryVk() function
        LoadGraphicsEngineVk(GetEngineFactoryVk);
#endif
        EngineVkCreateInfo EngineCI;
        auto* pFactoryVk = GetEngineFactoryVk();
        pFactoryVk->CreateDeviceAndContextsVk(EngineCI, &m_pDevice, &m_pImmediateContext);
        pFactoryVk->CreateSwapChainVk(m_pDevice, m_pImmediateContext,
                                      SCDesc, NativeWindowHandle, &m_pSwapChain);
    }
    break;

    default:
        std::cerr << "Unknown device type";
    }
}

On Windows, the engine can be statically linked to the application or built as a separate DLL. In the former case, factory functions GetEngineFactoryOpenGL(), GetEngineFactoryD3D11(), GetEngineFactoryD3D12(), and GetEngineFactoryVk() can be called directly. In the latter case, you need to load the DLL into the process's address space using LoadGraphicsEngineOpenGL(), LoadGraphicsEngineD3D11(), LoadGraphicsEngineD3D12(), or LoadGraphicsEngineVk() function. Each function loads appropriate dynamic library and imports the functions required to initialize the engine. You need to include the following headers:

#include "EngineFactoryD3D11.h"
#include "EngineFactoryD3D12.h"
#include "EngineFactoryOpenGL.h"
#include "EngineFactoryVk.h"

You also need to add the following directories to the include search paths:

DiligentCore/Graphics/GraphicsEngineD3D11/interface
DiligentCore/Graphics/GraphicsEngineD3D12/interface
DiligentCore/Graphics/GraphicsEngineOpenGL/interface
DiligentCore/Graphics/GraphicsEngineVulkan/interface

Also, enable Diligent namespace:

using namespace Diligent;

IEngineFactoryD3D11::CreateDeviceAndContextsD3D11(), IEngineFactoryD3D12::CreateDeviceAndContextsD3D12(), and IEngineFactoryVk::CreateDeviceAndContextsVk() functions can also create a specified number of deferred contexts, which can be used for multi-threaded command recording. Deferred contexts can only be created during the initialization of the engine. The function populates an array of pointers to the contexts, where the immediate context goes at position 0, followed by all deferred contexts.

For more details, take a look at Tutorial00_HelloWin32.cpp file.

Universal Windows Platform

On Universal Windows Platform, you can create Direct3D11 or Direct3D12 device. Only static linking is currently supported, but dynamic linking can also be implemented. Initialization is performed the same way as on Win32 Platform. The difference is that you first create the render device and device contexts by calling IEngineFactoryD3D11::CreateDeviceAndContextsD3D11() or IEngineFactoryD3D12::CreateDeviceAndContextsD3D12(). The swap chain is created later by a call to IEngineFactoryD3D11::CreateSwapChainD3D11() or IEngineFactoryD3D12::CreateSwapChainD3D12(). Please look at SampleAppUWP.cpp file for more details.

Linux

On Linux platform, the engine supports OpenGL and Vulkan backends. Initialization of GL context on Linux is tightly coupled with window creation. As a result, Diligent Engine does not initialize the context, but attaches to the one initialized by the app. An example of the engine initialization on Linux can be found in Tutorial00_HelloLinux.cpp.

MacOS

On MacOS, Diligent Engine supports OpenGL, Vulkan and Metal backends. Initialization of GL context on MacOS is performed by the application, and the engine attaches to the context created by the app; see GLView.m for details. Vulkan backend is initialized similar to other platforms. See MetalView.m.

Android

On Android, you can create OpenGLES or Vulkan device. The following code snippet shows an example:

auto* pFactoryOpenGL = GetEngineFactoryOpenGL();
EngineGLCreateInfo EngineCI;
EngineCI.Window.pAWindow = NativeWindowHandle;
pFactoryOpenGL->CreateDeviceAndSwapChainGL(
    EngineCI, &m_pDevice, &m_pContext, SCDesc, &m_pSwapChain);
IRenderDeviceGLES *pRenderDeviceOpenGLES;
pRenderDevice->QueryInterface(IID_RenderDeviceGLES, reinterpret_cast<IObject**>(&pRenderDeviceOpenGLES));

If engine is built as dynamic library, the library needs to be loaded by the native activity. The following code shows one possible way:

static
{
    try{
        System.loadLibrary("GraphicsEngineOpenGL");
    } catch (UnsatisfiedLinkError e) {
        Log.e("native-activity", "Failed to load GraphicsEngineOpenGL library.\n" + e);
    }
}

iOS

iOS implementation supports OpenGLES and Metal backend. Initialization of GL context on iOS is performed by the application, and the engine attaches to the context initialized by the app; see EAGLView.m for details.

Attaching to Already Initialized Graphics API

An alternative way to initialize the engine is to attach to existing D3D11/D3D12 device or OpenGL/GLES context. Refer to Native API interoperability for more details.

Destroying the Engine

The engine performs automatic reference counting and shuts down when the last reference to an engine object is released.

Creating Resources

Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. To create a buffer, you need to populate BufferDesc structure and call IRenderDevice::CreateBuffer(). The following code creates a uniform (constant) buffer:

BufferDesc BuffDesc;
BuffDesc.Name           = "Uniform buffer";
BuffDesc.BindFlags      = BIND_UNIFORM_BUFFER;
BuffDesc.Usage          = USAGE_DYNAMIC;
BuffDesc.uiSizeInBytes  = sizeof(ShaderConstants);
BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE;
m_pDevice->CreateBuffer(BuffDesc, nullptr, &m_pConstantBuffer);

Similar, to create a texture, populate TextureDesc structure and call IRenderDevice::CreateTexture() as in the following example:

TextureDesc TexDesc;
TexDesc.Name      = "My texture 2D";
TexDesc.Type      = TEXTURE_TYPE_2D;
TexDesc.Width     = 1024;
TexDesc.Height    = 1024;
TexDesc.Format    = TEX_FORMAT_RGBA8_UNORM;
TexDesc.Usage     = USAGE_DEFAULT;
TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS;
TexDesc.Name = "Sample 2D Texture";
m_pRenderDevice->CreateTexture(TexDesc, nullptr, &m_pTestTex);

There is only one function CreateTexture() that is capable of creating all types of textures. Type, format, array size and all other parameters are specified by the members of the TextureDesc structure.

For every bind flag specified during the texture creation time, the texture object creates a default view. Default shader resource view addresses the entire texture, default render target and depth stencil views reference all array slices in the most detailed mip level, and unordered access view references the entire texture. To get a default view from the texture, use ITexture::GetDefaultView() function. Note that this function does not increment the reference counter on the returned interface. You can create additional texture views using ITexture::CreateView(). Use IBuffer::CreateView() to create additional views of a buffer.

Creating Shaders

To create a shader, populate ShaderCreateInfo structure:

ShaderCreateInfo ShaderCI;

There are two ways to create a shader. The first way is to provide a pointer to the shader source code through ShaderCreateInfo::Source member. The second way is to provide a file name. Graphics Engine is entirely decoupled from the platform. Since the host file system is platform-dependent, the structure exposes ShaderCreateInfo::pShaderSourceStreamFactory member that is intended to give the engine access to the file system. If you provided the source file name, you must also provide a non-null pointer to the shader source stream factory. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. You can however define your own implementation.

An important member is ShaderCreateInfo::SourceLanguage. The following are valid values for this member:

SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source format matches the underlying graphics API: HLSL for D3D11 or D3D12 mode, and GLSL for OpenGL, OpenGLES, and Vulkan modes.
SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. In Vulkan back-end, the code will be compiled to SPIRV directly.
SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL.

Other members of the ShaderCreateInfo structure define shader include search directories, shader macro definitions, shader entry point and other parameters.

ShaderMacroHelper Macros;
Macros.AddShaderMacro("USE_SHADOWS", 1);
Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4);
Macros.Finalize();
ShaderCI.Macros = Macros;

When everything is ready, call IRenderDevice::CreateShader() to create the shader object:

ShaderCreateInfo ShaderCI;
ShaderCI.Desc.Name         = "MyPixelShader";
ShaderCI.FilePath          = "MyShaderFile.fx";
ShaderCI.EntryPoint        = "MyPixelShader";
ShaderCI.Desc.ShaderType   = SHADER_TYPE_PIXEL;
ShaderCI.SourceLanguage    = SHADER_SOURCE_LANGUAGE_HLSL;
const auto* SearchDirectories = "shaders;shaders\\inc;";
RefCntAutoPtr<IShaderSourceInputStreamFactory> pShaderSourceFactory;
m_pEngineFactory->CreateDefaultShaderSourceStreamFactory(SearchDirectories, &pShaderSourceFactory);
ShaderCI.pShaderSourceStreamFactory = pShaderSourceFactory;
RefCntAutoPtr<IShader> pShader;
m_pDevice->CreateShader(ShaderCI, &pShader);

Initializing Pipeline State

Diligent Engine follows Direct3D12/Vulkan style to configure the graphics/compute pipeline. One monolithic Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.). To create a pipeline state object, define an instance of GraphicsPipelineStateCreateInfo structure:

GraphicsPipelineStateCreateInfo PSOCreateInfo;
PipelineStateDesc&              PSODesc = PSOCreateInfo.PSODesc;

PSODesc.Name = "My pipeline state";

Describe the pipeline specifics such as if the pipeline is a compute pipeline, number and format of render targets as well as depth-stencil format:

// This is a graphics pipeline
PSODesc.PipelineType                            = PIPELINE_TYPE_GRAPHICS;
PSOCreateInfo.GraphicsPipeline.NumRenderTargets = 1;
PSOCreateInfo.GraphicsPipeline.RTVFormats[0]    = TEX_FORMAT_RGBA8_UNORM_SRGB;
PSOCreateInfo.GraphicsPipeline.DSVFormat        = TEX_FORMAT_D32_FLOAT;

Initialize depth-stencil state description structure DepthStencilStateDesc. Note that the constructor initializes the members with default values and you may only set the ones that are different from default.

// Init depth-stencil state
DepthStencilStateDesc& DepthStencilDesc = PSOCreateInfo.GraphicsPipeline.DepthStencilDesc;
DepthStencilDesc.DepthEnable            = true;
DepthStencilDesc.DepthWriteEnable       = true;

Initialize blend state description structure BlendStateDesc:

// Init blend state
BlendStateDesc& BSDesc = PSOCreateInfo.GraphicsPipeline.BlendDesc;
BSDesc.IndependentBlendEnable = False;
auto &RT0 = BSDesc.RenderTargets[0];
RT0.BlendEnable           = True;
RT0.RenderTargetWriteMask = COLOR_MASK_ALL;
RT0.SrcBlend              = BLEND_FACTOR_SRC_ALPHA;
RT0.DestBlend             = BLEND_FACTOR_INV_SRC_ALPHA;
RT0.BlendOp               = BLEND_OPERATION_ADD;
RT0.SrcBlendAlpha         = BLEND_FACTOR_SRC_ALPHA;
RT0.DestBlendAlpha        = BLEND_FACTOR_INV_SRC_ALPHA;
RT0.BlendOpAlpha          = BLEND_OPERATION_ADD;

Initialize rasterizer state description structure RasterizerStateDesc:

// Init rasterizer state
RasterizerStateDesc& RasterizerDesc = PSOCreateInfo.GraphicsPipeline.RasterizerDesc;
RasterizerDesc.FillMode              = FILL_MODE_SOLID;
RasterizerDesc.CullMode              = CULL_MODE_NONE;
RasterizerDesc.FrontCounterClockwise = True;
RasterizerDesc.ScissorEnable         = True;
RasterizerDesc.AntialiasedLineEnable = False;

Initialize input layout description structure InputLayoutDesc:

// Define input layout
InputLayoutDesc& Layout = PSOCreateInfo.GraphicsPipeline.InputLayout;
LayoutElement LayoutElems[] =
{
    LayoutElement( 0, 0, 3, VT_FLOAT32, False ),
    LayoutElement( 1, 0, 4, VT_UINT8,   True ),
    LayoutElement( 2, 0, 2, VT_FLOAT32, False ),
};
Layout.LayoutElements = LayoutElems;
Layout.NumElements    = _countof(LayoutElems);

Define primitive topology and set shader pointers:

// Define shader and primitive topology
PSOCreateInfo.GraphicsPipeline.PrimitiveTopology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST;
PSOCreateInfo.pVS = m_pVS;
PSOCreateInfo.pPS = m_pPS;

Pipeline Resource Layout

Pipeline resource layout informs the engine how the application is going to use different shader resource variables. To allow grouping of resources based on the frequency of expected change, Diligent Engine introduces classification of shader variables:

Static variables (SHADER_RESOURCE_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers.
Mutable variables (SHADER_RESOURCE_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc.
Dynamic variables (SHADER_RESOURCE_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly.

To define variable types, prepare an array of ShaderResourceVariableDesc structures and initialize PSODesc.ResourceLayout.Variables and PSODesc.ResourceLayout.NumVariables members. Also PSODesc.ResourceLayout.DefaultVariableType can be used to set the type that will be used if a variable name is not provided.

ShaderResourceVariableDesc ShaderVars[] =
{
    {SHADER_TYPE_PIXEL, "g_StaticTexture",  SHADER_RESOURCE_VARIABLE_TYPE_STATIC},
    {SHADER_TYPE_PIXEL, "g_MutableTexture", SHADER_RESOURCE_VARIABLE_TYPE_MUTABLE},
    {SHADER_TYPE_PIXEL, "g_DynamicTexture", SHADER_RESOURCE_VARIABLE_TYPE_DYNAMIC}
};
PSODesc.ResourceLayout.Variables           = ShaderVars;
PSODesc.ResourceLayout.NumVariables        = _countof(ShaderVars);
PSODesc.ResourceLayout.DefaultVariableType = SHADER_RESOURCE_VARIABLE_TYPE_STATIC;

When creating a pipeline state, textures can be permanently assigned static samplers. If a static sampler is assigned to a texture, it will always be used instead of the one initialized in the texture shader resource view. To define static samplers, prepare an array of StaticSamplerDesc structures and intialize PSODesc.ResourceLayout.StaticSamplers and PSODesc.ResourceLayout.NumStaticSamplers members. Notice that static samplers can be assigned to a texture variable of any type, not necessarily static, so that the texture binding can be changed at run-time, while the sampler will stay immutable. It is highly recommended to use static samplers whenever possible.

StaticSamplerDesc StaticSampler;
StaticSampler.ShaderStages   = SHADER_TYPE_PIXEL;
StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR;
StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR;
StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR;
StaticSampler.TextureName    = "g_MutableTexture";
PSODesc.ResourceLayout.NumStaticSamplers = 1;
PSODesc.ResourceLayout.StaticSamplers    = &StaticSampler;

When all required fields of PSO description structure are set, call IRenderDevice::CreateGraphicsPipelineState() to create the PSO object:

m_pDevice->CreateGraphicsPipelineState(PSOCreateInfo, &m_pPSO);

Binding Shader Resources

As mentioned above, shader resource binding in Diligent Engine is based on grouping variables in 3 different groups (static, mutable and dynamic). Static variables are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. They are bound directly to the Pipeline State Object:

m_pPSO->GetStaticShaderVariable(SHADER_TYPE_PIXEL, "g_tex2DShadowMap")->Set(pShadowMapSRV);

Mutable and dynamic variables are bound via a new object called Shader Resource Binding (SRB), which is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):

m_pPSO->CreateShaderResourceBinding(&m_pSRB, true);

The second parameter tells the system to initialize internal structures in the SRB object that reference static variables in the PSO.

Dynamic and mutable resources are then bound through SRB object:

m_pSRB->GetVariable(SHADER_TYPE_PIXEL,  "tex2DDiffuse")->Set(pDiffuseTexSRV);
m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB);

The difference between mutable and dynamic resources is that mutable ones can only be set once for every instance of a shader resource binding. Dynamic resources can be set multiple times. It is important to properly set the variable type as this affects performance. Static variables are generally most efficient, followed by mutable. Dynamic variables are most expensive from performance point of view.

An alternative way to bind shader resources is to create IResourceMapping interface that maps resource literal names to the actual resources:

ResourceMappingEntry Entries[] =
{
    {"g_Texture", pTexture->GetDefaultView(TEXTURE_VIEW_SHADER_RESOURCE)},
    ResourceMappingEntry{}
};
ResourceMappingDesc ResMappingDesc;
ResMappingDesc.pEntries= Entries;
RefCntAutoPtr<IResourceMapping> pResMapping;
pRenderDevice->CreateResourceMapping( ResMappingDesc, &pResMapping );

The resource mapping can then be used to bind all static resources in a pipeline state (IPipelineState::BindStaticResources()):

m_pPSO->BindStaticResources(SHADER_TYPE_VERTEX | SHADER_TYPE_PIXEL, pResMapping, BIND_SHADER_RESOURCES_VERIFY_ALL_RESOLVED);

or all mutable and dynamic resources in a shader resource binding (IShaderResourceBinding::BindResources()):

m_pSRB->BindResources(SHADER_TYPE_VERTEX | SHADER_TYPE_PIXEL, pResMapping, BIND_SHADER_RESOURCES_VERIFY_ALL_RESOLVED);

The last parameter to all BindResources() functions defines how resources should be resolved:

BIND_SHADER_RESOURCES_UPDATE_STATIC - Indicates that static variable bindings are to be updated.
BIND_SHADER_RESOURCES_UPDATE_MUTABLE - Indicates that mutable variable bindings are to be updated.
BIND_SHADER_RESOURCES_UPDATE_DYNAMIC -Indicates that dynamic variable bindings are to be updated.
BIND_SHADER_RESOURCES_UPDATE_ALL - Indicates that all variable types (static, mutable and dynamic) are to be updated. Note that if none of BIND_SHADER_RESOURCES_UPDATE_STATIC, BIND_SHADER_RESOURCES_UPDATE_MUTABLE, and BIND_SHADER_RESOURCES_UPDATE_DYNAMIC flags are set, all variable types are updated as if BIND_SHADER_RESOURCES_UPDATE_ALL was specified.
BIND_SHADER_RESOURCES_KEEP_EXISTING - If this flag is specified, only unresolved bindings will be updated. All existing bindings will keep their original values. If this flag is not specified, every shader variable will be updated if the mapping contains corresponding resource.
BIND_SHADER_RESOURCES_VERIFY_ALL_RESOLVED - If this flag is specified, all shader bindings are expected be resolved after the call. If this is not the case, an error will be reported.

BindResources() may be called several times with different resource mappings to bind resources. However, it is recommended to use one large resource mapping as the size of the mapping does not affect element search time.

The engine performs run-time checks to verify that correct resources are being bound. For example, if you try to bind a constant buffer to a shader resource view variable, an error will be output to the debug console.

Setting the Pipeline State and Invoking Draw Command

Before any draw command can be invoked, all required vertex and index buffers as well as the pipeline state should be bound to the device context:

// Set render targets before issuing any draw command.
auto* pRTV = m_pSwapChain->GetCurrentBackBufferRTV();
auto* pDSV = m_pSwapChain->GetDepthBufferDSV();
m_pContext->SetRenderTargets(1, &pRTV, pDSV, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);

// Clear render target and depth-stencil
const float zero[4] = {0, 0, 0, 0};
m_pContext->ClearRenderTarget(pRTV, ClearColor, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
m_pContext->ClearDepthStencil(pDSV, CLEAR_DEPTH_FLAG, 1.f, 0, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);

// Set vertex and index buffers
IBuffer* buffer[] = {m_pVertexBuffer};
Uint32 offsets[] = {0};
m_pContext->SetVertexBuffers(0, 1, buffer, offsets, SET_VERTEX_BUFFERS_FLAG_RESET,
                             RESOURCE_STATE_TRANSITION_MODE_TRANSITION);
m_pContext->SetIndexBuffer(m_pIndexBuffer, 0, RESOURCE_STATE_TRANSITION_MODE_TRANSITION);

m_pContext->SetPipelineState(m_pPSO);

All methods that may need to perform resource state transitions take RESOURCE_STATE_TRANSITION_MODE enum as parameter. The enum defines the following modes:

RESOURCE_STATE_TRANSITION_MODE_NONE - Perform no resource state transitions.
RESOURCE_STATE_TRANSITION_MODE_TRANSITION - Transition resources to the states required by the command.
RESOURCE_STATE_TRANSITION_MODE_VERIFY - Do not transition, but verify that states are correct.

The final step is to committ shader resources to the device context. This is accomplished by the IDeviceContext::CommitShaderResources() method:

m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES);

If the method is not called, the engine will detect that resources are not committed and output debug message. Note that CommitShaderResources() must be called after the right pipeline state has been bound to the context. Note that the last parameter tells the system to transition resources to correct states. If this flag is not specified, the resources must be explicitly transitioned to required states by a call to IDeviceContext::TransitionShaderResources():

m_pContext->TransitionShaderResources(m_pPSO, m_pSRB);

Note that the method requires pointer to the pipeline state that created the shader resource binding.

When all required states and resources are bound, IDeviceContext::Draw() can be used to execute draw command or IDeviceContext::DispatchCompute() can be used to execute compute command. Note that for a draw command, graphics pipeline must be bound, and for dispatch command, compute pipeline must be bound. Draw() takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:

DrawAttribs attrs;
attrs.IndexType  = VT_UINT16;
attrs.NumIndices = 36;
attrs.Flags      = DRAW_FLAG_VERIFY_STATES;
pContext->Draw(attrs);

DRAW_FLAG_VERIFY_STATES flag instructs the engine to verify that vertex and index buffers used by the draw command are transitioned to proper states.

DispatchCompute() takes DispatchComputeAttribs structure that defines compute grid dimensions:

m_pContext->SetPipelineState(m_pComputePSO);
m_pContext->CommitShaderResources(m_pComputeSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES);
DispatchComputeAttribs DispatchAttrs(64, 64, 8);
m_pContext->DispatchCompute(DispatchAttrs);

You can learn more about the engine API by looking at the engine samples' source code and the API Reference.

Low-level API interoperability

Diligent Engine extensively supports interoperability with underlying low-level APIs. The engine can be initialized by attaching to existing D3D11/D3D12 device or OpenGL/GLES context and provides access to the underlying native API objects. Refer to the following pages for more information:

Direct3D11 Interoperability

Direct3D12 Interoperability

OpenGL/GLES Interoperability

Repository structure

The repository contains the following projects:

Project	Description
Primitives	Definitions of basic types (Int32, Int16, Uint32, etc.) and interfaces (IObject, IReferenceCounters, etc.)
Common	Common functionality such as file wrapper, logging, debug utilities, etc.
Graphics/GraphicsAccessories	Basic graphics accessories used by all implementations
Graphics/GraphicsEngine	Platform-independent base functionality
Graphics/GraphicsEngineD3DBase	Base functionality for D3D11/D3D12 implementations
Graphics/GraphicsEngineD3D11	Implementation of Direct3D11 rendering backend
Graphics/GraphicsEngineD3D12	Implementation of Direct3D12 rendering backend
Graphics/GraphicsEngineOpenGL	Implementation of OpenGL/GLES rendering backend
Graphics/GraphicsEngineVulkan	Implementation of Vulkan rendering backend
Graphics/GraphicsEngineMetal	Implementation of Metal rendering backend
Graphics/GraphicsTools	Graphics utilities build on top of core interfaces (definitions of commonly used states, texture uploaders, etc.)
Graphics/HLSL2GLSLConverterLib	HLSL to GLSL source code converter library
Platforms/Basic	Interface for platform-specific routines and implementation of some common functionality
Platforms/Android	Implementation of platform-specific routines on Android
Platforms/Apple	Implementation of platform-specific routines on Apple platforms (MacOS, iOS)
Platforms/UWP	Implementation of platform-specific routines on Universal Windows platform
Platforms/Win32	Implementation of platform-specific routines on Win32 platform
Platforms/Linux	Implementation of platform-specific routines on Linux platform
External	Third-party libraries and modules

License

See Apache 2.0 license.

This project has some third-party dependencies, each of which may have independent licensing:

Vulkan-Headers: Vulkan Header files and API registry (Apache License 2.0).
SPIRV-Cross: SPIRV parsing and cross-compilation tools (Apache License 2.0).
SPIRV-Headers: SPIRV header files (Khronos MIT-like license).
SPIRV-Tools: SPIRV optimization and validation tools (Apache License 2.0).
glslang: Khronos reference compiler and validator for GLSL, ESSL, and HLSL (3-Clause BSD License, 2-Clause BSD License, MIT, Apache License 2.0).
glew: OpenGL Extension Wrangler Library (Mesa 3-D graphics library, Khronos MIT-like license).
volk: Meta loader for Vulkan API (Arseny Kapoulkine MIT-like license).
stb: stb single-file public domain libraries for C/C++ (MIT License or public domain).
googletest: Google Testing and Mocking Framework (BSD 3-Clause "New" or "Revised" License).
DirectXShaderCompiler: LLVM/Clang-based DirectX Shader Compiler (LLVM Release License).
DXBCChecksum: DXBC Checksum computation algorithm by AMD Developer Tools Team (MIT lincesne).

Contributing

To contribute your code, submit a Pull Request to this repository. Diligent Engine is distributed under the Apache 2.0 license that guarantees that content in the DiligentCore repository is free of Intellectual Property encumbrances. In submitting any content to this repository, you license that content under the same terms, and you agree that the content is free of any Intellectual Property claims and you have the right to license it under those terms.

Diligent Engine uses clang-format to ensure consistent source code style throught the code base. The format is validated by appveyor and travis for each commit and pull request, and the build will fail if any code formatting issue is found. Please refer to this page for instructions on how to set up clang-format and automatic code formatting.