EVE Frontier test bed yields CORTAO, an open-source ambient occlusion technique from Fenris Creations - eGamers.io
Fenris Creations has released CORTAO, an open-source ambient occlusion technique developed by Senior Rendering Engineer Daniel Isheden, available through the Carbon engine or standalone GitHub repository under MIT license.
Released on November 12, 2026, CORTAO (Circular Occluder Ray-Traced Ambient Occlusion) represents a breakthrough in rendering techniques for dynamic game environments. The technique was developed through the Carbon engine framework that Fenris Creations open-sourced earlier this year and has been extensively tested in EVE Frontier, the studio's space survival MMO still in development.
Real-time Shading for Dynamic Worlds
Unlike traditional ambient occlusion techniques, CORTAO calculates shading in real time without requiring baked scene data. This makes it particularly suitable for EVE Frontier, where players continuously build and reshape structures. The studio claims the technique reduces dark halos and unstable shading that commonly appear around objects in dynamic environments.
Small errors in shading can make an otherwise convincing scene feel wrong, especially when they become visible as the camera moves.
Technical Innovation
CORTAO introduces a fresh approach to screen-space ambient occlusion by treating nearby surfaces as circular occluders. The technique samples depth information near each pixel, converts valid samples into circular proxy occluders, and uses a precomputed lookup table to determine how much ambient light those proxies block. Each pixel can cast up to 32 rays, with the fraction of rays passing through determining the final shading.
The most challenging aspect was optimizing the technique to run fast enough for real-time rendering. CORTAO is designed as a drop-in replacement for existing screen-space ambient occlusion stages, making it accessible to developers regardless of their engine choice.
Superior Performance
In testing against Ground Truth Ambient Occlusion (GTAO), CORTAO demonstrated superior results. Using a recreated San Miguel cafe scene, a four-sample CORTAO implementation achieved a lower mean squared error against a ray-traced reference than any GTAO configuration tested. The technique also maintained more consistent occlusion as sample counts changed and showed fewer heavy halos and view-dependent artifacts.
The development began as independent research by Isheden after encountering problems with GTAO, particularly when rendering vegetation. Fenris Creations provided him with a production environment to test and refine the technique at scale.
Open Source Release
CORTAO's code is released under the MIT license, with both a standalone repository and a Carbon-optimized version available on GitHub. The EVE Frontier website hosts documentation and visual comparisons, while a YouTube video demonstrates the technique in action. Ben Hunter, Director of Core Technology at Fenris, explained that making the technique open source allows other teams to examine the decisions behind it and adapt it to challenges Fenris hasn't encountered.
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