Windows 10: DirectX Raytracing and the Windows 10 October 2018 Update

Brink · Oct 9, 2018

The wait is finally over: we’re taking DirectX Raytracing (DXR) out of experimental mode!

Today, once you update to the next release of Windows 10, DirectX Raytracing will work out-of-box on supported hardware. And speaking of hardware, the first generation of graphics cards with native raytracing support is already available and works with the October 2018 Windows Update.

The first wave of DirectX Raytracing in games is coming soon, with the first three titles that support our API: Battlefield V, Metro Exodus and Shadow of the Tomb Raider. Gamers will be able to have raytracing on their machines in the near future!

Raytracing and Windows

We’ve worked for many years to make Windows the best platform for PC Gaming and believe that DirectX Raytracing is a major leap forward for gamers on our platform. We built DirectX Raytracing with ubiquity in mind: it’s an API that was built to work across hardware from all vendors.

Real-time raytracing is often quoted as being the holy grail of graphics and it’s a key part of a decades-long dream to achieve realism in games. Today marks a key milestone in making this dream a reality: gamers now have access to both the OS and hardware to support real-time raytracing in games. With the first few titles powered by DirectX Raytracing just around the corner, we’re about to take the first step into a raytraced future.

This was made possible with hard work here at Microsoft and the great partnerships that we have with the industry. Without the solid collaboration from our partners, today’s announcement would not have been possible.

What does this mean for gaming?

DirectX Raytracing allows games to achieve a level of realism unachievable by traditional rasterization. This is because raytracing excels in areas where traditional rasterization is lacking, such as reflections, shadows and ambient occlusion. We specifically designed our raytracing API to be used alongside rasterization-based game pipelines and for developers to be able to integrate DirectX Raytracing support into their existing engines, without the need to rebuild their game engines from the ground up.

The difference that raytracing makes to a game is immediately apparent and this is something that the industry recognizes: DXR is one of the fastest adopted features that we’ve released in recent years.

Several studios have partnered with our friends at NVIDIA, who created RTX technology to make DirectX Raytracing run as efficiently as possible on their hardware:

EA’s Battlefield V will have support for raytraced reflections.

These reflections are impossible in real-time games that use rasterization only: raytraced reflections include assets that are off-screen, adding a whole new level of immersion as seen in the image above.

Shadow of the Tomb Raider will have DirectX Raytracing-powered shadows.

The shadows in Shadow of the Tomb Raider showcase DirectX Raytracing's ability to render lifelike shadows and shadow interactions that more realistic than what’s ever been showcased in a game.

Metro Exodus will use DirectX Raytracing for global illumination and ambient occlusion

Metro Exodus will have high-fidelity natural lighting and contact shadows, resulting in an environment where light behaves just as it does in real life.

These games will be followed by the next wave of titles that make use of raytracing.

We’re still in the early days of DirectX Raytracing and are excited not just about the specific effects that have already been implemented using our API, but also about the road ahead.

DirectX Raytracing is well-suited to take advantage of today’s trends: we expect DXR to open an entirely new class of techniques and revolutionize the graphics industry.

DirectX Raytracing and hardware trends

Hardware has become increasingly flexible and general-purpose over the past decade: with the same TFLOPs today’s GPU can do more and we only expect this trend to continue.

We designed DirectX Raytracing with this in mind: by representing DXR as a compute-like workload, without complex state, we believe that the API is future-proof and well-aligned with the future evolution of GPUs: DXR workloads will fit naturally into the GPU pipelines of tomorrow.

DirectML

DirectX Raytracing benefits not only from advances in hardware becoming more general-purpose, but also from advances in software.

In addition to the progress we’ve made with DirectX Raytracing, we recently announced a new public API, DirectML, which will allow game developers to integrate inferencing into their games with a low-level API. To hear more about this technology, releasing in Spring 2019, check out our SIGGRAPH talk.

ML techniques such as denoising and super-resolution will allow hardware to achieve impressive raytraced effects with fewer rays per pixel. We expect DirectML to play a large role in making raytracing more mainstream.

DirectX Raytracing and Game Development

Developers in the future will be able to spend less time with expensive pre-computations generating custom lightmaps, shadow maps and ambient occlusion maps for each asset.

Realism will be easier to achieve for game engines: accurate shadows, lighting, reflections and ambient occlusion are a natural consequence of raytracing and don’t require extensive work refining and iterating on complicated scene-specific shaders.

EA’s SEED division, the folks who made the PICA PICA demo, offer a glimpse of what this might look like: they were able to achieve an extraordinarily high level of visual quality with only three artists on their team!

Crossing the Uncanny Valley

We expect the impact of widespread DirectX Raytracing in games to be beyond achieving specific effects and helping developers make their games faster.

The human brain is hardwired to detect realism and is especially sensitive to realism when looking at representations of people: we can intuitively feel when a character in a game looks and feels “right”, and much of this depends on accurate lighting. When a character gets really close to looking as a real human should, but slightly misses the mark, it becomes unnerving to look at. This effect is known as the uncanny valley.

Because true-to-life lighting is a natural consequence of raytracing, DirectX Raytracing will allow games to get much closer to crossing the uncanny valley, allowing developers to blur the line between the real and the fake. Games that fully cross the uncanny valley will gave gamers total immersion in their virtual environments and interactions with in-game characters. Simply put, DXR will make games much more believable.
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Source: DirectX Raytracing and the Windows 10 October 2018 Update DirectX Developer Blog

See also: Announcing Microsoft DirectX Raytracing - Windows 10 Forums

:)

Brink · Oct 9, 2018

Announcing Microsoft DirectX Raytracing

3D Graphics is a Lie

For the last thirty years, almost all games have used the same general technique—rasterization—to render images on screen. While the internal representation of the game world is maintained as three dimensions, rasterization ultimately operates in two dimensions (the plane of the screen), with 3D primitives mapped onto it through transformation matrices. Through approaches like z-buffering and occlusion culling, games have historically strived to minimize the number of spurious pixels rendered, as normally they do not contribute to the final frame. And in a perfect world, the pixels rendered would be exactly those that are directly visible from the camera:

Figure 1a: a top-down illustration of various pixel reduction techniques. Top to bottom: no culling, view frustum culling, viewport clipping

Figure 1b: back-face culling, z-buffering

Through the first few years of the new millennium, this approach was sufficient. Normal and parallax mapping continued to add layers of realism to 3D games, and GPUs provided the ongoing improvements to bandwidth and processing power needed to deliver them. It wasn’t long, however, until games began using techniques that were incompatible with these optimizations. Shadow mapping allowed off-screen objects to contribute to on-screen pixels, and environment mapping required a complete spherical representation of the world. Today, techniques such as screen-space reflection and global illumination are pushing rasterization to its limits, with SSR, for example, being solved with level design tricks, and GI being solved in some cases by processing a full 3D representation of the world using async compute. In the future, the utilization of full-world 3D data for rendering techniques will only increase.

Figure 2: a top-down view showing how shadow mapping can allow even culled geometry to contribute to on-screen shadows in a scene

Today, we are introducing a feature to DirectX 12 that will bridge the gap between the rasterization techniques employed by games today, and the full 3D effects of tomorrow. This feature is DirectX Raytracing. By allowing traversal of a full 3D representation of the game world, DirectX Raytracing allows current rendering techniques such as SSR to naturally and efficiently fill the gaps left by rasterization, and opens the door to an entirely new class of techniques that have never been achieved in a real-time game. Readers unfamiliar with rasterization and raytracing will find more information about the basics of these concepts in the appendix below.

What is DirectX Raytracing?

At the highest level, DirectX Raytracing (DXR) introduces four, new concepts to the DirectX 12 API:

The acceleration structure is an object that represents a full 3D environment in a format optimal for traversal by the GPU. Represented as a two-level hierarchy, the structure affords both optimized ray traversal by the GPU, as well as efficient modification by the application for dynamic objects.

A new command list method, DispatchRays, which is the starting point for tracing rays into the scene. This is how the game actually submits DXR workloads to the GPU.

A set of new HLSL shader types including ray-generation, closest-hit, any-hit, and miss shaders. These specify what the DXR workload actually does computationally. When DispatchRays is called, the ray-generation shader runs. Using the new TraceRayintrinsic function in HLSL, the ray generation shader causes rays to be traced into the scene. Depending on where the ray goes in the scene, one of several hit or miss shaders may be invoked at the point of intersection. This allows a game to assign each object its own set of shaders and textures, resulting in a unique material.

The raytracing pipeline state, a companion in spirit to today’s Graphics and Compute pipeline state objects, encapsulates the raytracing shaders and other state relevant to raytracing workloads.

You may have noticed that DXR does not introduce a new GPU engine to go alongside DX12’s existing Graphics and Compute engines. This is intentional – DXR workloads can be run on either of DX12’s existing engines. The primary reason for this is that, fundamentally, DXR is a compute-like workload. It does not require complex state such as output merger blend modes or input assembler vertex layouts. A secondary reason, however, is that representing DXR as a compute-like workload is aligned to what we see as the future of graphics, namely that hardware will be increasingly general-purpose, and eventually most fixed-function units will be replaced by HLSL code. The design of the raytracing pipeline state exemplifies this shift through its name and design in the API. With DX12, the traditional approach would have been to create a new CreateRaytracingPipelineState method. Instead, we decided to go with a much more generic and flexible CreateStateObject method. It is designed to be adaptable so that in addition to Raytracing, it can eventually be used to create Graphics and Compute pipeline states, as well as any future pipeline designs.

Anatomy of a DXR Frame

The first step in rendering any content using DXR is to build the acceleration structures, which operate in a two-level hierarchy. At the bottom level of the structure, the application specifies a set of geometries, essentially vertex and index buffers representing distinct objects in the world. At the top level of the structure, the application specifies a list of instance descriptions containing references to a particular geometry, and some additional per-instance data such as transformation matrices, that can be updated from frame to frame in ways similar to how games perform dynamic object updates today. Together, these allow for efficient traversal of multiple complex geometries.

Figure 3: Instances of 2 geometries, each with its own transformation matrix

The second step in using DXR is to create the raytracing pipeline state. Today, most games batch their draw calls together for efficiency, for example rendering all metallic objects first, and all plastic objects second. But because it’s impossible to predict exactly what material a particular ray will hit, batching like this isn’t possible with raytracing. Instead, the raytracing pipeline state allows specification of multiple sets of raytracing shaders and texture resources. Ultimately, this allows an application to specify, for example, that any ray intersections with object A should use shader P and texture X, while intersections with object B should use shader Q and texture Y. This allows applications to have ray intersections run the correct shader code with the correct textures for the materials they hit.

The third and final step in using DXR is to call DispatchRays, which invokes the ray generation shader. Within this shader, the application makes calls to the TraceRay intrinsic, which triggers traversal of the acceleration structure, and eventual execution of the appropriate hit or miss shader. In addition, TraceRay can also be called from within hit and miss shaders, allowing for ray recursion or “multi-bounce” effects.

Figure 4: an illustration of ray recursion in a scene

Note that because the raytracing pipeline omits many of the fixed-function units of the graphics pipeline such as the input assembler and output merger, it is up to the application to specify how geometry is interpreted. Shaders are given the minimum set of attributes required to do this, namely the intersection point’s barycentric coordinates within the primitive. Ultimately, this flexibility is a significant benefit of DXR; the design allows for a huge variety of techniques without the overhead of mandating particular formats or constructs.

PIX for Windows Support Available on Day 1

As new graphics features put an increasing array of options at the disposal of game developers, the need for great tools becomes increasingly important. The great news is that PIX for Windows will support the DirectX Raytracing API from day 1 of the API’s release. PIX on Windows supports capturing and analyzing frames built using DXR to help developers understand how DXR interacts with the hardware. Developers can inspect API calls, view pipeline resources that contribute to the raytracing work, see contents of state objects, and visualize acceleration structures. This provides the information developers need to build great experiences using DXR.

What Does This Mean for Games?

DXR will initially be used to supplement current rendering techniques such as screen space reflections, for example, to fill in data from geometry that’s either occluded or off-screen. This will lead to a material increase in visual quality for these effects in the near future. Over the next several years, however, we expect an increase in utilization of DXR for techniques that are simply impractical for rasterization, such as true global illumination. Eventually, raytracing may completely replace rasterization as the standard algorithm for rendering 3D scenes. That said, until everyone has a light-field display on their desk, rasterization will continue to be an excellent match for the common case of rendering content to a flat grid of square pixels, supplemented by raytracing for true 3D effects.

Thanks to our friends at SEED, Electronic Arts, we can show you a .

Project PICA PICA from SEED, Electronic Arts

In addition, while today marks the first public announcement of DirectX Raytracing, we have been working closely with hardware vendors and industry developers for nearly a year to design and tune the API. In fact, a significant number of studios and engines are already planning to integrate DXR support into their games and engines, including:

Electronic Arts, Frostbite

Electronic Arts, SEED

Epic Games, Unreal Engine

Futuremark, 3DMark

Unity Technologies, Unity Engine

And more will be coming soon.

What Hardware Will DXR Run On?

Developers can use currently in-market hardware to get started on DirectX Raytracing. There is also a fallback layer which will allow developers to start experimenting with DirectX Raytracing that does not require any specific hardware support. For hardware roadmap support for DirectX Raytracing, please contact hardware vendors directly for further details.

Available now for experimentation!

Want to be one of the first to bring real-time raytracing to your game? Start by attending our Game Developer Conference Session on DirectX Raytracing for all the technical details you need to begin, then download the Experimental DXR SDK and start coding! Not attending GDC? No problem! We'll be posting the slides on this blog after the session.
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Read more: Announcing Microsoft DirectX Raytracing! DirectX Developer Blog

StefanM · Oct 9, 2018

DirectX Raytracing Tutorials

This repository contain tutorials demonstrating how to use DirectX Raytracing. Under the Tutorials folder you can find Word documents going over the code, explaining how to use the API.

Requirements:

Windows 10 RS4. Follow the instructions on the DirectX forums.

Windows 10 SDK 10.0.16299.91.

Visual Studio 2015.

You do not need to download the DXR SDK, it is packaged with the tutorials.

Open the solution, build it, knock yourself out.

Unsurprisingly the samples don't run on Redstone 3 (missing procedure entry points in runtimes).
I'll recheck next month with Redstone 4.

WenzhaoPeng2981 · Oct 9, 2018

Windows 10 October 2018 Update

When is the official windows 10 October 2018 update releases?

Windows 10: DirectX Raytracing and the Windows 10 October 2018 Update

DirectX Raytracing and the Windows 10 October 2018 Update

DirectX Raytracing and the Windows 10 October 2018 Update

DirectX Raytracing and the Windows 10 October 2018 Update

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