Diligent Engine: A Modern Cross-Platform Low-Level Graphics Library

Disclaimer: This article uses material published on Diligent Engine web site.

• Download latest source (Github)

Background

This post talks about graphics APIs, so some knowledge of Direct3D11, Direct3D12, OpenGL or Vulkan is desirable.

Introduction

Graphics APIs have come a long way from a small set of basic commands allowing limited control of configurable stages of early 3D accelerators to very low-level programming interfaces exposing almost every aspect of the underlying graphics hardware. The next-generation APIs, Direct3D12 by Microsoft and Vulkan by Khronos are relatively new and have only started getting widespread adoption and support from hardware vendors, while Direct3D11 and OpenGL are still considered industry standard. New APIs can provide substantial performance and functional improvements, but may not be supported by older platforms. An application targeting wide range of platforms has to support Direct3D11 and OpenGL. New APIs will not give any advantage when used with old paradigms. It is totally possible to add Direct3D12 support to an existing renderer by implementing Direct3D11 interface through Direct3D12, but this will give zero benefits. Instead, new approaches and rendering architectures that leverage flexibility provided by the next-generation APIs are expected to be developed.

There exist at least four APIs (Direct3D11, Direct3D12, OpenGL/GLESplus, Vulkan, plus Apple's Metal for iOS and OSX platforms) that a cross-platform 3D application may need to support. Writing separate code paths for all APIs is clearly not an option for any real-world application and the need for a cross-platform graphics abstraction layer is evident. The following is the list of requirements that I believe such layer needs to meet:

• Lightweight abstractions: The API should be as close to the underlying native APIs as possible to allow the application to leverage all available low-level functionality. In many cases, this requirement is difficult to achieve because specific features exposed by different APIs may vary considerably.
• Low performance overhead: The abstraction layer needs to be efficient from the performance point of view. If it introduces a considerable amount of overhead, there is no point in using it.
• Convenience: The API needs to be convenient to use. It needs to assist developers in achieving their goals not limiting their control of the graphics hardware.
• Multithreading: The ability to efficiently parallelize work is in the core of Direct3D12 and Vulkan and one of the main selling points of the new APIs. Support for multithreading in a cross-platform layer is a must.
• Extensibility: no matter how well the API is designed, it still introduces some level of abstraction. In some cases, the most efficient way to implement some functionality is to directly use native API. The abstraction layer needs to provide access to the underlying native API objects to provide a way for the app to add features that may be missing.

This article describes Diligent Engine, a light-weight cross-platform graphics API abstraction layer that is designed to solve these problems. Its main goal is to take advantages of the next-generation APIs such as Direct3D12, Vulkan, Metal and WebGPU, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common C/C++ front-end for all supported platforms and provides interoperability with underlying native APIs. It also supports integration with Unity and is designed to be used as graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. The full source code is available for download at GitHub and is free to use. The engine currently supports the following platforms and low-level graphics APIs:

Overview

Diligent Engine API takes some features from Direct3D11 and Direct3D12 as well as introduces new concepts. It contains the following main components:

Render device (IRenderDevice interface) is responsible for creating all other objects (textures, buffers, shaders, pipeline states, etc.).

Device context (IDeviceContext interface) is the main interface for rendering command recording. Similar to Direct3D11, there are immediate context and deferred contexts (that in D3D11 implementation map directly to the corresponding context types). Immediate context combines command queue and command list recording functionality. It records commands and submits the command list for execution when it contains sufficient number of commands. Deferred contexts are designed to only record command lists that can be submitted for execution through the immediate context.

An alternative way to design the API would be to expose command queue and command lists directly. This approach however does not map well to Direct3D11 and OpenGL. Besides, some functionality (such as dynamic descriptor allocation) can be much more efficiently implemented when it is known that a command list is recorded by a certain deferred context from some thread.

The approach taken in the engine does not limit scalability as the application is expected to create one deferred context per thread, and internally every deferred context records a command list in lock-free fashion. At the same time, this approach maps well to older APIs.

In the current implementation, only one immediate context that uses default graphics command queue is created. To support multiple GPUs or multiple command queue types (compute, copy, etc.), it is natural to have one immediate context per queue. Cross-context synchronization utilities will be necessary.

Swap Chain (ISwapChain interface). Swap chain interface represents a chain of back buffers and is responsible for showing the final rendered image on the screen.

Render device, device contexts and swap chain are created during the engine initialization.

Resources (ITexture and IBuffer interfaces). There are two types of resources - textures and buffers. There are many different texture types (2D textures, 3D textures, texture array, cubempas, etc.) that can all be represented by ITexture interface.

Resources Views (ITextureView and IBufferView interfaces). While textures and buffers are mere data containers, texture views and buffer views describe how the data should be interpreted. For instance, a 2D texture can be used as a render target for rendering commands or as a shader resource.

Pipeline State (IPipelineState interface). GPU pipeline contains many configurable stages (depth-stencil, rasterizer and blend states, different shader stage, etc.). Direct3D11 uses coarse-grain objects to set all stage parameters at once (for instance, a rasterizer object encompasses all rasterizer attributes), while OpenGL contains myriad functions to fine-grain control every individual attribute of every stage. Both methods do not map very well to modern graphics hardware that combine all states into one monolithic state under the hood. Direct3D12/Vulkan directly expose pipeline state object in the API, and Diligent Engine uses the same approach.

Shader Resource Binding (IShaderResourceBinding interface). Shaders are programs that run on the GPU. Shaders may access various resources (textures and buffers), and setting correspondence between shader variables and actual resources is called resource binding. Resource binding implementation varies considerably between different API. Diligent Engine introduces a new object called shader resource binding that encompasses all resources needed by all shaders in a certain pipeline state.

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. Graphics APIs usually have a native object that represents linear buffer. Diligent Engine uses IBuffer interface as an abstraction for a native buffer. To create a buffer, one needs to populate BufferDesc structure and call IRenderDevice::CreateBuffer() method as in the following example:

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);

While there is usually just one buffer object, different APIs use very different approaches to represent textures. For instance, in Direct3D11, there are texture 1D, texture 2D, and texture 3D objects. In OpenGL, there is individual object for every texture dimension that may also be a texture array that may also be multisampled (such as GL_TEXTURE_2D_MULTISAMPLE_ARRAY). As a result, there are nine different GL texture types that Diligent Engine may create under the hood. For Direct3D12, there is only one resource interface. Diligent Engine hides all these details in ITexture interface. There is only one IRenderDevice::CreateTexture() method that is capable of creating all texture types. Dimension, format, array size and all other parameters are specified by the members of the TextureDesc structure:

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;
m_pRenderDevice->CreateTexture(TexDesc, nullptr, &m_pTestTex);

If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.

Next-generation APIs allow fine-level control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.

Creating Shaders

While in earlier APIs, shaders were separate objects, in the next-generation APIs as well as in Diligent Engine, shaders are part of the pipeline state. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL.

To create a shader, populate ShaderCreateInfo structure:

ShaderCreateInfo ShaderCI;

SourceLanguage member of this structure tells the system which language the shader is authored in:

• SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 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. Vulkan backend compiles HLSL code directly to SPIRV.
• SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL, OpenGLES and Vulkan modes.

There are two ways to provide shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. 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. Custom implementation can be provided when needed.

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

ShaderCI.Desc.Name         = "MyPixelShader";
ShaderCI.FilePath          = "MyShaderFile.fx";
ShaderCI.EntryPoint        = "MyPixelShader";
ShaderCI.Desc.ShaderType   =  SHADER_TYPE_PIXEL;
ShaderCI.SourceLanguage    = SHADER_SOURCE_LANGUAGE_HLSL;

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

const auto* SearchDirectories = "shaders;shaders\\inc;";
BasicShaderSourceStreamFactory BasicSSSFactory(SearchDirectories);
ShaderCI.pShaderSourceStreamFactory = &BasicSSSFactory;


RefCntAutoPtr<IShader> pShader;
m_pDevice->CreateShader( Attrs, &pShader );

Initializing the Pipeline State

As it was mentioned earlier, Diligent Engine follows next-gen APIs to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions, etc.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings, it is very easy to forget to set one of the states or assume the stage is already properly configured when in reality it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.

To create a pipeline state object, define instance of PipelineStateCreateInfo structure:

PipelineStateCreateInfo PSOCreateInfo;
PipelineStateDesc& PSODesc = PSOCreateInfo.PSODesc;
PSODesc.Name = "My pipeline state";

The fields of the PipelineStateDesc structure provide details about the pipeline state, such as depth-stencil, rasterizer, and blend state descriptions, number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:

RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc;
RasterizerDesc.FillMode              = FILL_MODE_SOLID;
RasterizerDesc.CullMode              = CULL_MODE_NONE;
RasterizerDesc.FrontCounterClockwise = True;
RasterizerDesc.ScissorEnable         = True;
RasterizerDesc.AntialiasedLineEnable = False;

Depth-stencil and blend states are defined in a similar fashion.

Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:

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

Finally, pipeline state defines primitive topology.

// Define shader and primitive topology
PSODesc.GraphicsPipeline.PrimitiveTopology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST;
PSODesc.GraphicsPipeline.pVS = pVertexShader;
PSODesc.GraphicsPipeline.pPS = pPixelShader;

Pipeline Resource Layout

Pipeline state object also defines shader resource layout (see below) that informs the engine how different shader variables are expected to be used by the application.

When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases, it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a PSO, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible.

The following is an example of pipeline resource layout definition:

ShaderResourceVariableDesc ShaderVars[] =
{
    {SHADER_TYPE_PIXEL, "g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},
    {SHADER_TYPE_PIXEL, "g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},
    {SHADER_TYPE_PIXEL, "g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC}
};
PSODesc.ResourceLayout.Variables           = ShaderVars;
PSODesc.ResourceLayout.NumVariables        = _countof(ShaderVars);
PSODesc.ResourceLayout.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC;

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 members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method.

m_pDevice->CreatePipelineState(PSOCreateInfo, &m_pPSO);

When a PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object.

Binding Shader Resources

Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command context. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:

• 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.

Shader variable type must be specified during PSO creation by preparing an array of ShaderResourceVariableDesc structures and initializing PSODesc.ResourceLayout.Variables and PSODesc.ResourceLayout.NumVariables members (see example above).

Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the PSO object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:

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

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

m_pPSO->CreateShaderResourceBinding(&m_pSRB, true);

An SRB is compatible with any pipeline state that has the same resource layout. SRB object inherits all static bindings from PSO, but is not allowed to change them.

Mutable resources can only be set once for every instance of shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:

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

In some cases, it is necessary to bind a new resource to a variable every time draw command is invoked. Such variables should be labelled as dynamic, which will allow setting them multiple times through the same SRB object:

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

Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB object is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.

As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.

This post gives more details about the resource binding model in Diligent Engine.

Setting the Pipeline State and Committing Shader Resources

Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:

m_pContext->SetPipelineState(m_pPSO);

Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.

The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:

m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES);

The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.

Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking. When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct state at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:

m_pContext->TransitionShaderResources(m_pPSO, m_pSRB);

In some scenarios, it is more efficient to transition resources once and then only commit them.

Invoking Draw Command

The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:

ITextureView *pRTVs[] = {m_pRTV};
m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV,
                             RESOURCE_STATE_TRANSITION_MODE_TRANSITION);

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

Note that 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 state transitions
• RESOURCE_STATE_TRANSITION_MODE_TRANSITION - Transition all resources to the states required by the command
• RESOURCE_STATE_TRANSITION_MODE_VERIFY - Do not transition, but verify that states are correct

Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used, etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, 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.IsIndexed  = true;
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 in correct states. It is recommended to always use this flag unless there is race condition in a multithreaded environment.

For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.

Source Code

The full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses DiligentEngine in native plugin.

Features

• Cross-platform
  • Exact same client code for all supported platforms and rendering backends
    • No #if defined(_WIN32) ... #elif defined(LINUX) ... #elif defined(ANDROID) ...
    • No #if defined(D3D11) ... #elif defined(D3D12) ... #elif defined(OPENGL) ...
  • Exact same HLSL shaders run on all platforms and all backends
• Modular design
  • Components are clearly separated logically and physically and can be used as needed
  • Only take what you need for your project (do not want to keep samples and tutorials in your codebase? Simply remove Samples submodule. Only need core functionality? Use only Core submodule)
  • No 15000 lines-of-code files
• Clear object-based interface
  • No global states
• Key graphics features:
  • Automatic shader resource binding designed to leverage the next-generation rendering APIs
  • Multithreaded command buffer generation
    • 50,000 draw calls at 300 fps with D3D12 backend
  • Descriptor, memory and resource state management
• Modern C++ features to make code fast and reliable

Tutorials

Below is the list of tutorials that are currently implemented.

Tutorial		Description
01_Triangle ▶️ Run in the browser		This basic tutorial shows how to render a simple triangle using Diligent Engine API.
02_Cube ▶️ Run in the browser		This tutorial demonstrates how to render an actual 3D object, a cube. It shows how to load shaders from files, create and use vertex, index and uniform buffers.
03_Texturing ▶️ Run in the browser		This tutorial demonstrates how to apply a texture to a 3D object. It shows how to load a texture from file, create shader resource binding object and how to sample a texture in the shader.
03_Texturing-C		This tutorial is identical to Tutorial03, but is implemented using C API.
03_Texturing-DotNet		This tutorial demonstrates how to use the Diligent Engine API in .NET applications.
04_Instancing ▶️ Run in the browser		This tutorial shows how to use instancing to render multiple copies of one object using unique transformation matrix for every copy.
05_TextureArray ▶️ Run in the browser		This tutorial demonstrates how to combine instancing with texture arrays to use unique texture for every instance.
06_Multithreading ▶️ Run in the browser		This tutorial shows how to generate command lists in parallel from multiple threads.
07_GeometryShader		This tutorial shows how to use geometry shader to render smooth wireframe.
08_Tessellation		This tutorial shows how to use hardware tessellation to implement simple adaptive terrain rendering algorithm.
09_Quads ▶️ Run in the browser		This tutorial shows how to render multiple 2D quads, frequently switching textures and blend modes.
10_Streaming ▶️ Run in the browser		This tutorial shows dynamic buffer mapping strategy using MAP_FLAG_DISCARD and MAP_FLAG_DO_NOT_SYNCHRONIZE flags to efficiently stream varying amounts of data to GPU.
11_ResourceUpdates ▶️ Run in the browser		This tutorial demonstrated different ways to update buffers and textures in Diligent Engine and explains important internal details and performance implications related to each method.
Tutorial12_RenderTarget ▶️ Run in the browser		This tutorial demonstrates how to render a 3d textured cube into an offscreen render target and do a simple distortion post-processing effect.
Tutorial13_ShadowMap ▶️ Run in the browser		This tutorial demonstrates how to render basic shadows using a shadow map.
Tutorial14_ComputeShader ▶️ Run in the browser		This tutorial shows how to implement a simple particle simulation system using compute shaders.
Tutorial15_MultiWindows		This tutorial demonstrates how to use Diligent Engine to render to multiple windows.
Tutorial16_BindlessResources ▶️ Run in the browser		This tutorial shows how to implement bindless resources, a technique that leverages dynamic shader resource indexing feature enabled by the next-gen APIs to significantly improve rendering performance.
Tutorial17_MSAA ▶️ Run in the browser		This tutorial demonstrates how to use multisample anti-aliasing (MSAA) to make geometrical edges look smoother and more temporarily stable.
Tutorial18_Queries ▶️ Run in the browser		This tutorial demonstrates how to use queries to retrieve various information about the GPU operation, such as the number of primitives rendered, command processing duration, etc.
Tutorial19_RenderPasses ▶️ Run in the browser		This tutorial demonstrates how to use the render passes API to implement simple deferred shading.
Tutorial20_MeshShader		This tutorial deomstrates how to use amplification and mesh shaders, the new programmable stages of modern GPUs, to implement frustum culling and LOD calculation on the GPU.
Tutorial21_RayTracing		This tutorial demonstrates how ray tracing API in Diligent Engine can be used to simulate physics-based light transport in a scene to render soft shadows, multiple-bounce reflections and refractions, and dispersion.
Tutorial22_HybridRendering		This tutorial demonstrates how to implement a simple hybrid renderer that combines rasterization with ray tracing.
Tutorial23_CommandQueues		This tutorial demonstrates how to use multiple command queues to perform rendering in parallel with copy and compute operations.
Tutoria24_VRS		This tutorial demonstrates how to use variable rate shading to reduce the pixel shading load.
Tutoria25_StatePackager		This tutorial shows how to create and archive pipeline states with the render state packager off-line tool on the example of a simple path tracer.
Tutoria26_StateCache ▶️ Run in the browser		This tutorial expands the path tracing technique implemented in previous tutorial and demonstrates how to use the render state cache to save pipeline states created at run time and load them when the application starts.
Tutorial27_PostProcessing ▶️ Run in the browser		This tutorial demonstrates how to use post-processing effects (screen-space reflections, ambient occlusion, depth of field, etc.) from the DiligentFX module..

Samples

Atmospheric light scattering sample implements physically-based atmospheric light scattering model and demonstrates how Diligent Engine can be used to accomplish various rendering tasks: loading textures from files, using complex shaders, rendering to textures, using compute shaders and unordered access views, etc.

▶️ Run in the browser

GLFW Minigame

GLFW mini-game shows how to use Diligent Engine with the GLFW, a popular window and input handling library.

GLTF Viewer

GLTF viewer shows how to use the GLTF Asset Loader and Physically-based Renderer to load and render GLTF models.

▶️ Run in the browser

Shadows

Shadows sample shows how to use the shadowing component to render high-quality shadows.

▶️ Run in the browser

Dear Imgui Demo

The sample demonstrates the integration of the engine with Dear Imgui UI library.

▶️ Run in the browser

Nuklear Demo

This sample demonstrates the integration of the engine with nuklear UI library.

Hello AR

This sample demonstrates how to use Diligent Engine in a basic Android AR application.

Asteroids Benchmark

The engine also includes Asteroids performance benchmark based on this demo developed by Intel. It renders 50,000 unique textured asteroids and let's compare performance of D3D11, D3D12, and Vulkan implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

Unity Integration Sample

The repository also contains an example project that shows how Diligent Engine can be integrated with Unity.

Future Work

The engine is under active development. It currently supports all major platforms (Windows desktop, Universal Windows, Linux, MacOS, Android, and iOS). Direct3D11, Direct3D12, OpenGL/GLES, and Vulkan backends are now complete. Several advanced features such as ray tracing support, multiple command queues, render passes are planned.

Related Articles

• Managing Lifetimes of Direct3D12 Resources
• Managing Descriptor Heaps in Direct3D12
• Implementing Dynamic Resources with Direct3D12
• Comparing GPU Resource Update Strategies in Diligent Engine
• Unity Graphics Emulator for Native Plugin Development
• More Explicit Diligent Engine: Getting on top of State Management in Direct3D12 and Vulkan

Version History

• September 1, 2024 - Diligent now supports WebGPU, added links to run samples in the browser
• May 5, 2024 - Added tutorial 27 - Post Processing
• August 9, 2023 - Added tutorial 03 version for Dot Net
• December 4, 2022 - Added advanced path tracing / render state cache tutorial
• August 29, 2022 - Added path tracing / state packager tutorial
• October 11, 2021 - Added variable rate shading tutorial
• August 16, 2021 - Added command queues tutorial
• June 06, 2021 - Added hybrid rendering tutorial
• Jan 03, 2021 - Added ray-tracing tutorial
• May 14, 2020 - Added Hello AR sample
• Februrary 04, 2020 - Enabled C API and added C version of Tutorial 03
• January 14, 2020 - Added Tutorial 18
• November 11, 2019 - Added Tutorial 17 and Nuklear Demo
• October 13, 2019 - Added Tutorials 14 & 15 and Dear Imgui Demo.
• July 24, 2019 - Added Shadows sample.
• May 07, 2019 - Added GLTF Viewer sample and Tutorial 12 - Render Target.
• April 03, 2019 - Diligent Engine supports Vulkan on iOS; replaced static images with animations.
• March 09, 2019 - Updated article to match release v2.4.b