DOOM: The Dark Ages pushes real-time graphics to latest limits by integrating RTX neural rendering and path tracing, setting a brand new standard for a way modern games balance visual ambition with fast, fluid gameplay. To explore the motivations, solutions, and lessons from overcoming these technical challenges, we spoke with Billy Khan, the director of engine technology at id Software.
Why did id Software resolve to integrate path tracing into DOOM: The Dark Ages?
Path tracing is the subsequent logical advancement in ray-traced visuals, and we’re desirous to push the boundaries of lighting improvements in id Tech 8 (game engine used for DOOM: The Dark Ages). Demonstrating cutting-edge visual techniques in a commercially released game is crucial, because it holds more significance than showcasing them in a meticulously crafted, academic demo environment.
A brand new rendering technique is barely truly viable if it may possibly be integrated inside the constraints of a shipping product, ensuring it really works harmoniously with the prevailing rendering pipeline without introducing noticeable artifacts. Scalability across a big selection of hardware configurations is a core mission for us. We prioritize developing impactful features for each current and future high-end GPUs, while also ensuring the sport performs optimally across a big selection of devices.
What are the advantages of path tracing in comparison with ray tracing?
Path tracing is more computationally expensive than ray tracing—it’s a level-up of current ray tracing techniques. The added costs deliver more realistic, physically accurate lighting and surface shading.
Dynamic RTX Global Illumination is more accurate with path tracing than with probe-based ray tracing solutions. Path tracing handles indirect emissive light contributions on surfaces higher, produces more realistic, softer shadows, and generates more accurate reflections on rough surfaces. Overall, ray tracing provides improbable results, but path tracing takes image quality and immersion to the subsequent level.
What motivated your team to optimize GPU surface shading and integrate latest rendering solutions?
For top-performance, visually complex scenes, optimizing each surface shading and transparency is crucial. Techniques that allow the GPU to intelligently reorder shading work and skip unnecessary calculations—like on pixels fully occluded by alpha-tested geometry—yield significant speedups. Each NVIDIA Opacity Micro-Map (OMM) and Shader Execution Reordering (SER) have been extremely useful for optimizing surface shading on the GPU. A few of our biggest optimizations for path tracing resulted from utilizing shader execution reordering.
What are the advantages from OMM and SER?
Opacity Micro-Map advantages any style of alpha-tested graphical workload—common examples include vegetation and particle systems. OMM reduces the shading rate by encoding the shading needs of micro-triangles onto larger triangles. This information is then used to short-circuit and avoid shading any pixels which might be either fully transparent or opaque.
Shader Execution Reordering (SER), alternatively, allows the GPU to optimize the order during which various kinds of shading work are performed, improving efficiency in scenes with complex lighting and materials. Each techniques are versatile tools for developers pushing the bounds of real-time graphics.
How long did it take to implement path tracing?
From start to complete, it took about six months to implement and ship path tracing in DOOM: The Dark Ages.
Do you propose to integrate path tracing into future titles?
Absolutely. Path tracing is now a part of id Tech 8. We’ll proceed research and development on this area. As with all technology, we evaluate its use on a per-game basis to make sure it meets the needs of the sport and delivers value to players. I imagine path tracing will proceed to evolve and might be used in additional games in the approaching years.
How has DLSS 4 modified your approach to image quality and game performance?
DLSS 4 brought in the brand new transformer model, which made significant improvements to super resolution and denoising that we were capable of leverage in DOOM: The Dark Ages. Using the brand new transformer model with path tracing, Super Resolution and Ray Reconstruction can work in tandem, which not only improves the standard of upsampled pixels, but in comparison to traditional denoisers, combining the 2 also improves performance. DLSS 4’s Multi Frame Generation enhances smoothness and may boost frame rates sufficiently to fulfill or surpass the utmost refresh rates of players’ display devices.
How invaluable is DLSS Ray Reconstruction?
DLSS Ray Reconstruction added much-needed fidelity to denoising our path-traced results while preserving more detail. It’s a powerful improvement in performance and quality over traditional denoising techniques. I’m excited to see further innovation here, which can empower more devices to play games with higher visual fidelity.
Are you able to explain why transformer-based upscaling models outperform older convolutional neural networks (CNNs)?
There are three important points.
- Transformer models higher mix spatial and temporal data—motion vectors, depth information, and frame history—reducing ghosting and other artifacts in fast-moving games.
- Transformer models evaluate and model all pixels concurrently, whereas CNNs are more restricted, normally processing only smaller regions. This permits transformers to higher handle edges, resulting in improved image quality.
- Transformer models transcend easy pattern recognition, enabling more accurate reconstruction of surface details and shapes, which ultimately produces upsampled images with fewer artifacts.
Are you able to share any final suggestions or lessons learned for other developers seeking to integrate AI and path tracing technologies?
Leveraging super resolution and denoisers that use AI-backed transformer models can significantly boost performance while preserving (or improving) image quality and backbone. I like to recommend starting with general ray tracing to know its implications in your rendering pipelines. Optimal path tracing solutions are frequently built on a sturdy ray tracing infrastructure, because it’s more GPU-demanding.
Keep your total shader count and complexity as little as possible for the most effective performance. Memory costs increase when using ray tracing and path tracing, since geometries should be stored in bounding volume hierarchies (BVH). It’s vital to know the price differences between fully rebuilding BVH structures and refitting them—refits will be as much as 10x faster. Understanding the connection between your bottom-level acceleration structures (BLAS) and top-level acceleration structures (TLAS) can be key. A number of the highest costs for ray tracing and path tracing come from shading pixels—Shader Execution Reordering may also help here, alongside traditional shading optimizations.
Get Began with Neural Rendering in Your Game
As seen in DOOM: The Dark Ages, leveraging innovations like neural rendering technologies empowers developers to push the boundaries of real-time graphics performance and fidelity—advancing each technology and the player experience.
See our full list of neural rendering and AI resources for game developers here.
