Microsoft increases ray tracing speed in DirectX 12 to 90 % thanks to a new ray processing order

Microsoft has introduced a new DirectX feature – Shader Execution Reordering (SER)

At the recent Game Developers Conference 2025, the company announced the release of DXR 1.2, which for the first time includes the SER mechanism. This technology allows optimization of ray‑tracing tasks that are responsible for realistic lighting, reflections, and shadows in modern games.

What Changed
Previously, ray tracing was performed “chaotically” – each ray is processed independently. A developer can indicate similarity of calculations in shaders, and the GPU will automatically reorder their execution.
In the conventional mode, the GPU encounters tasks of varying complexity: some rays quickly hit objects, while others penetrate deeply and require significant time. This mixes “heavy” and “light” operations within a single thread, reducing parallel processing efficiency.

With SER, a developer can specify the order of thread execution in shader code (HLSL). The GPU then reorganizes tasks so that similar operations run consecutively, thereby increasing overall performance.

Technical Details
* New control – previously only the driver distributed the load; now developers can influence this process.
* HLSL primitives – new constructs were added to request ordering of thread processing.
* Shader Model 6.9 standard – SER support became mandatory, so all modern drivers must correctly handle such code. Efficiency depends on specific hardware.

Practical Result
Microsoft demonstrated SER’s effectiveness using the game *Alan Wake 2*, where it was used alongside the Opacity Micromaps (OMM) technology. As a result:
* Ray‑tracing performance increased by ≈30 %
→ higher frame rates for players.
→ ability to add additional visual effects for developers.

In tests on an Nvidia GeForce RTX 4090, the gain was about 40 %, and on some Intel Arc B series models up to 90 %.

How It Works
The traditional ray‑tracing algorithm consisted of two stages:
1. The ray tracing itself.
2. Collection and subsequent processing of hit information by shaders.

With SER, a developer can first perform the first stage for the entire scene, gather similar hit results, group them, and only then launch further processing in batches. This reduces system resource consumption and boosts GPU efficiency.

In summary:
Microsoft expanded DirectX by adding to DXR 1.2 the ability to control the order of ray‑tracing tasks. This opens new avenues for performance optimization and makes modern graphical effects more accessible to developers and players.