Introduction
I am excited to explore the cutting-edge advances that are enabling photorealistic real-time rendering with ray tracing. Ray tracing has long been considered the holy grail for creating highly realistic computer graphics, but has traditionally been too computationally intensive for real-time applications like video games. However, thanks to new GPU architectures and rendering techniques, real-time ray tracing is finally becoming practical.
In this article, I will provide an in-depth look at the key innovations driving this revolution in real-time photorealism. First, I will explain the basics of how ray tracing works and why it produces such realistic results. Next, I will discuss the hardware advances that are making real-time ray tracing achievable, particularly NVIDIA’s new RTX GPUs. I will then explore the software side, covering new algorithms like denoising that optimize ray tracing performance. Finally, I will show how these advances are being applied to create stunning photorealism in games and other real-time applications.
Along the way, I will use bold to highlight key terms and concepts, provide illustrative examples, and share insights from developers who are on the cutting edge of real-time photorealism. For readers eager to understand how we’ve arrived at this new era of ray tracing, this article offers a comprehensive look at the breakthroughs enabling previously impossible feats of real-time graphics. Let’s dive in!
How Ray Tracing Works
To understand the significance of real-time ray tracing, we first need to understand how ray tracing works at a fundamental level and why it produces such realistic results.
Ray tracing is a rendering technique that simulates the physical behavior of light by tracing the path that light would take if it were to travel through a scene. It works by casting individual light rays per pixel from the camera. Each ray is traced through the 3D scene, where it may intersect with and bounce off different objects. This produces effects like accurate reflections, refractions, shadows, global illumination and ambient occlusion that mimic real-world light behavior.
This contrasts with previous real-time rendering techniques like rasterization, which merely project the geometry directly to the screen without accurately simulating light. This allows rasterization to run fast, but prevents it from achieving the same level of realism as ray tracing.
Some key advantages of ray tracing:
- Realistic reflections and refractions
- Soft, natural shadows
- Accurate ambient occlusion and global illumination
- Photorealistic material qualities like metal, glass, liquids
By tracing light paths physically through a 3D scene, ray tracing can render photorealism on a level rasterization simply cannot match. That’s why it has long been used for high-end offline rendering in films and animation. But only now is this level of photorealism becoming possible in real-time applications.
Hardware Advances Making Real-Time Ray Tracing Possible
So what hardware innovations have enabled real-time ray tracing? The single most important factor is the development of GPUs specifically optimized for ray tracing workloads.
NVIDIA’s RTX GPU architecture represents a giant leap in this regard. RTX GPUs have dedicated ray tracing cores and AI-powered denoising capabilities that dramatically accelerate ray tracing performance.
Some key hardware features enabling real-time ray tracing on RTX GPUs:
- RT cores – Dedicated ray tracing cores to massively speed up intersection testing
- Tensor cores – AI processors that denoise rendered images using deep learning
- Ray tracing memory architecture – Improves efficiency of data structures used in ray tracing
Together, these hardware breakthroughs boost ray tracing speeds by up to 25-30x compared to traditional GPUs. This raw horsepower is what makes achieving real-time ray traced graphics possible.
NVIDIA has continued optimizing RTX GPUs for ray tracing in subsequent generations. For example, the new RTX 4090 GPU achieves up to 2-4x faster ray tracing speeds compared to the previous RTX 3090 flagship. Each new generation brings us closer to fully interactive photorealism.
Software Advances and Rendering Techniques
However, hardware is only half the equation. New software techniques have also been critical to making real-time ray tracing feasible.
AI Denoising
RTX GPUs use AI denoising powered by deep learning and Tensor cores to smooth out the inherent noise in ray traced images. This allows fewer samples per pixel to achieve clean results, greatly accelerating rendering. AI denoising has been key to achieving playable framerates with ray tracing enabled.
Variable Rate Shading
Variable rate shading (VRS) selectively reduces shading rate in areas of the image that don’t require full resolution. This improves performance while minimizing visual impact on quality. VRS enhances ray tracing speeds and allows more rays to be cast in important regions of the frame.
Foveated Rendering
Similar to VRS, foveated rendering concentrates rays in the focal point region being observed by the viewer. Fewer rays are traced towards the peripheral areas. This mimics how human vision works and again boosts performance with minimal perceptual loss in quality.
Asynchronous Ray Tracing
Asynchronous ray tracing queues and batches rays to trace in the background while the main GPU rasterizes the scene. The ray tracing results are then incorporated into subsequent frames. This technique hides much of the ray tracing latency and improves overall framerates.
Ray Tracing in Real-Time Applications
Thanks to these advances, ray tracing is becoming widely implemented to achieve real-time photorealism in games, simulations, VR and more.
Ray Traced Games
Gaming is an obvious application for real-time ray tracing. Ray traced effects like shadows, global illumination and accurate reflections add tremendous visual fidelity. Major game engines like Unreal Engine and Unity now support ray tracing integration, along with platforms like DirectX 12 and Vulkan.
Some notable games using real-time ray tracing:
- Cyberpunk 2077
- Call of Duty: Modern Warfare
- Watch Dogs: Legion
- Minecraft
Film & Animation
Ray tracing also offers benefits for content creation in film and animation. Ray traced previews can provide artists an accurate in-engine view of the final rendered scene while modeling assets and animating. This speeds up the creative workflow.
Virtual Reality
The advanced lighting effects provided by ray tracing are especially impactful in VR, where realistic visuals are key to achieving full immersion. NVIDIA’s VRWorks integrates ray tracing into the rendering pipeline specifically for VR applications.
As ray tracing performance continues improving, the possibilities are endless. Any application where photorealistic graphics are critical can benefit from the power of real-time ray tracing. After decades of development, this revolutionary rendering technique is finally ready for practical real-world use.
The Future of Real-Time Ray Tracing
In this article, we’ve covered the fundamentals of ray tracing, the hardware and software breakthroughs enabling real-time performance, and some current applications leveraging this technology. But what does the future hold as ray tracing continues evolving?
Fully Dynamic Ray Tracing
Right now, some effects like shadows and reflections use a hybrid of ray tracing with some baked-in elements. Fully dynamic ray tracing with no precomputation will further enhance realism. This is demanding, but performance is improving rapidly.
Increasing Ray Counts
Higher ray counts per pixel will keep improving image quality. Optimizations like foveated rendering will help concentrate rays where needed most.
Expanding Platform Support
Broader support in game engines, APIs, OSes, and development frameworks will make ray tracing more accessible to creators. We can expect integration beyond PC and consoles to platforms like mobile as performance scales down.
Cloud Compute Assistance
Supplementing local GPUs with cloud compute could provide on-demand ray tracing horsepower to devices with insufficient performance. This could bring ray traced graphics to a broader range of hardware.
Real-time ray tracing has come a long way in just a few years. As algorithms, GPU hardware, and software integration continue advancing rapidly, the possibilities are incredibly exciting. Photorealism previously only possible in offline rendering is coming to interactive applications. It’s the start of a new era in computer graphics!
