Direct3D 12 Graphics API

What is Direct3D 12?

Direct3D 12 (D3D12) is a low-overhead graphics API for Windows 10 and Xbox One. It provides developers with more direct control over the GPU, leading to improved performance and efficiency, especially in demanding graphics applications like games and professional visualization tools. D3D12 significantly reduces CPU overhead by allowing applications to batch draw calls and manage resources more effectively.

Key Features and Benefits

Reduced CPU Overhead: Explicitly manage command lists and submission, bypassing older API bottlenecks.
Multi-threaded Performance: Designed for modern multi-core processors, enabling parallel command generation.
Lower-Level GPU Control: Direct access to GPU hardware features and memory management.
Shader Model 6.0 Support: Advanced shader capabilities for more sophisticated visual effects.
Mesh Shaders & Amplification Shaders: New programmable stages for advanced geometry processing.
Ray Tracing Support: Integrated support for real-time ray tracing through DirectX Raytracing (DXR).

Core Concepts

Command Queue and Lists
Resource Management (Heaps, Buffers, Textures)
Pipeline State Objects (PSOs)
Root Signature
Descriptor Heaps
Synchronization Primitives (Fences)

Getting Started with Direct3D 12

Begin your journey with Direct3D 12 by exploring these essential resources:

Community Forums and Discussions

Engage with fellow developers, ask questions, and share your experiences:

Advanced Topics

Dive deeper into the intricacies of Direct3D 12:

Command Queue and Lists

Direct3D 12 introduces the concept of command queues and command lists. Applications record commands into command lists, which are then submitted to the GPU via a command queue. This allows for efficient batching and parallel execution.

                // Example C++ pseudo-code
                ID3D12CommandAllocator* pCommandAllocator;
                ID3D12GraphicsCommandList* pCommandList;

                // Create command allocator and list
                device->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT, IID_PPV_ARGS(&pCommandAllocator));
                device->CreateCommandList(0, D3D12_COMMAND_LIST_TYPE_DIRECT, pCommandAllocator, nullptr, IID_PPV_ARGS(&pCommandList));

                // Record commands
                pCommandList->ResourceBarrier(...);
                pCommandList->OMSetRenderTargets(...);
                pCommandList->DrawInstanced(...);

                // Close command list
                pCommandList->Close();

                // Submit to command queue
                ID3D12CommandQueue* pCommandQueue;
                // ... get command queue from device ...
                ID3D12CommandList* ppCommandLists[] = { pCommandList };
                pCommandQueue->ExecuteCommandLists(_countof(ppCommandLists), ppCommandLists);
                

Resource Management

Managing GPU memory and resources is crucial. D3D12 provides explicit control over resource allocation using heaps, buffers, and textures.

                // Example C++ pseudo-code
                ID3D12Resource* vertexBufferUpload;
                D3D12_HEAP_PROPERTIES heapProp = { ... }; // Upload heap
                D3D12_RESOURCE_DESC bufferDesc = { ... }; // Vertex buffer description

                device->CreateCommittedResource(&heapProp, D3D12_HEAP_FLAG_NONE, &bufferDesc, D3D12_RESOURCE_STATE_GENERIC_READ, nullptr, IID_PPV_ARGS(&vertexBufferUpload));
                // Map and copy data to the upload buffer
                

Pipeline State Objects (PSOs)

A Pipeline State Object encapsulates all the fixed-function and programmable-stage state required for rendering. This includes shaders, blend states, rasterizer states, depth-stencil states, and more.

                // Example C++ pseudo-code
                D3D12_GRAPHICS_PIPELINE_STATE_DESC psoDesc = {};
                // ... configure shaders, blend state, rasterizer state, etc. ...
                psoDesc.pRootSignature = m_rootSignature.Get();
                psoDesc.VS = { reinterpret_cast(vertexShaderBlob->GetBufferPointer()), vertexShaderBlob->GetBufferSize() };
                psoDesc.PS = { reinterpret_cast(pixelShaderBlob->GetBufferPointer()), pixelShaderBlob->GetBufferSize() };
                // ... other states ...

                ID3D12PipelineState* pso;
                device->CreateGraphicsPipelineState(&psoDesc, IID_PPV_ARGS(&pso));
                commandList->SetPipelineState(pso);
                

Root Signature

The Root Signature defines the root-level parameters that shaders can access, such as constant buffers, texture samplers, and shader resource views. It acts as an interface between the application and the shaders.

Descriptor Heaps

Descriptor heaps manage the memory for descriptors, which are small structures that point to GPU resources (like textures and buffers) and define how they are accessed by shaders.

Synchronization Primitives

Fences are used to synchronize the CPU and GPU. They allow the CPU to wait for specific GPU work to complete before proceeding.

                // Example C++ pseudo-code
                ID3D12Fence* fence;
                UINT64 fenceValue = 0;
                device->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(&fence));

                // Submit work and increment fence value
                commandQueue->ExecuteCommandLists(1, reinterpret_cast(&commandList), fence, fenceValue);
                fenceValue++;

                // Wait for fence completion
                if (fence->GetCompletedValue() < fenceValue) {
                    HANDLE eventHandle = CreateEvent(nullptr, FALSE, FALSE, nullptr);
                    fence->SetEventOnCompletion(fenceValue, eventHandle);
                    WaitForSingleObject(eventHandle, INFINITE);
                    CloseHandle(eventHandle);
                }
                

Windows Graphics API