In-Depth Analysis of RE Engine Path Tracing: SER, ReSTIR Global Illumination, and DLSS Ray Racing in Resident Evil Requiem and PRAGMATA

CAPCOM’s latest titles, PRAGMATA and Resident Evil Requiem, have marked a significant shift in graphics technology by being the inaugural games utilizing RE Engine with support for path tracing. During the recent GDC 2026 presentation titled “Real-Time Path Tracing in RE ENGINE for Resident Evil Requiem and PRAGMATA”, detailed insights into this cutting-edge adaptation were shared, making it a must-watch for graphics enthusiasts and developers alike.

This engaging presentation is accessible through the NVIDIA Game Developer YouTube channel. Unsurprisingly, NVIDIA played a crucial role in implementing path tracing within CAPCOM’s engine. The session featured Hitoshi Mishima from CAPCOM’s RE Engine team, who delved into the architectural and artistic aspects of the implementation, alongside Calvin Shu from NVIDIA, who shared insights about GPU performance optimizations specific to these two games.

On the CAPCOM front, the integration task was predominantly led by Kenta Nakamoto and Kosuke Nabata, who completed the project in around one and a half years. This advancement integrates closely with NVIDIA DLSS Ray Reconstruction, which enhances denoising capabilities and allows for efficient real-time performance, ultimately necessitating NVIDIA GeForce RTX hardware for these games.

The RE Engine previously supported ray tracing with the 2021 release of Resident Evil Village, which included features like ray traced global illumination, ambient occlusion, and reflections. However, it relied on rasterization for direct lighting and utilized ray tracing solely for indirect lighting. In contrast, full path tracing processes both direct and indirect lighting via a unified path-tracing pipeline, allowing for improved shadow detail, clearer reflections, more reliable denoising, and advanced ambient occlusion surpassing conventional ray tracing methods. The construction of the Bounding Volume Hierarchy (BVH) is executed using asynchronous compute, enabling shared ray query and material shader frameworks.

As the presentation progressed, technical details came into focus. CAPCOM adopted a streaming RIS technique to effectively prioritize the most important light sources. Key design decisions included:

• Brightness compensation was introduced to mitigate dark edges in brightly lit areas, utilizing reservoir updates for camera exposure adjustments.
• A simplified BSDF model (combining Lambertian diffuse with a single-lobe specular) was employed during candidate selection to reduce ALU costs.
• Image-Based Lighting (IBL) was excluded from the candidate set in indoor environments with high-intensity IBL, as these samples tended to be occluded, leading to high variance and degradation in DLSS Ray Reconstruction.
• Explicit NEE samples were incorporated using Walker’s Alias Method, enabling efficient triangle sampling based on area and intensity.

The RE Engine constructs a 3D grid (AABB) around each point light source, measuring 16×128×128 cells, which each hold a light ID bitmask. This allows the streaming RIS to reference the grid at each shading point, optimizing performance significantly by only evaluating relevant lights.

The development team incorporated the ReSTIR GI technique to enhance the stability of DLSS Ray Reconstruction’s quality, significantly diminishing noise levels in indirect lighting. This technique allows for the reuse of path samples across frames; previous frame paths are resampled while current frame paths are stored at each pixel.

To prevent excessive correlation with Ray Reconstruction, samples are drawn from slightly offset positions relative to the previous frame rather than exact pixel matches. This strategy allowed various scenes in both Resident Evil Requiem and PRAGMATA to be illuminated using IBL only, resulting in markedly reduced noise levels.

Additionally, the presentation highlighted how the DLSS Ray Reconstruction guide buffer was employed to rectify specific visual artifacts, such as:

• Subsurface scattering: Issues arose with ghosting artifacts in hair areas due to the SSS blur pass. A solution involved encoding luminance discrepancies before and after scattering into the guide buffer for proper adjustment.
• Frosted glass: Similar artifact types were encountered on frosted surfaces, which were also addressed by the SSS guide buffer technique.
• Raindrops and transparent decals: The disocclusion handling mechanism made raindrops appear almost invisible. The solution involved utilizing the disocclusion mask to compute normals before and after decal application.
• Animated projection texture lights: Ray Reconstruction had difficulties with rapidly altering animated light patterns on surfaces; RIS animation weights were modulated against overall weights to optimize this.
• Holograms: Emissive color animations in holograms weren’t accurately represented in the guide buffer, causing blurring. Adjustments were made to replace diffuse and specular albedo in the guide buffer with the emissive color.

Both Resident Evil Requiem and PRAGMATA utilize CAPCOM’s proprietary strand hair technology, first showcased in Resident Evil 4 Remake (2023) and refined thereafter. This approach employs a hybrid hardware and software rasterization pipeline, allowing thicker hair clumps to undergo classification and culling, proceeded by hardware rasterization for denser strands and software semi-transparency for finer wisps. In ray tracing, a fallback mesh replaces full strand geometry in the BVH. Notably, PRAGMATA escalates this to a formal strand BVH to better accommodate the lead character’s flowing long hair.

Calvin Shu concluded the presentation by discussing the optimization process demonstrated using a test scene from PRAGMATA that showcased DLSS Ray Reconstruction, DLAA, and RTX 5090 capabilities at 4K resolution. This particular scene featured 73 analytical lights and 32 emissive samples from a 4K array.

The path tracing optimization journey in the RE Engine was anything but linear, with notable regression points arising from the Shader Execution Reordering (SER) implementation. The investigation discovered that merging two compute shader passes into a unified dispatch ray call inadvertently created instruction duplication, compounding performance issues. Transitioning to bindless addresses these inefficiencies, showcasing a significant turnaround in optimization.

As the presentation wrapped up, Calvin Shu emphasized the importance of adopting DXR 1.2 with Shader Execution Reordering for future path-trace implementations. This approach could achieve “Speed of Light“throughput, representing NVIDIA’s ambitious GPU performance target. He further introduced the forthcoming 2.0 version of the DLSS Ray Reconstruction Disocclusion Mask, anticipated to refine edge case handling experienced in Resident Evil Requiem and PRAGMATA.

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