EVE Online Dev Open-Sources Its Physically Based SSAO Technology
CORTAO is now available for you to explore, integrate, and build upon.
Fenris Creations, the studio best known for EVE Online, has introduced CORTAO (Circular Occluder Ray-Traced Ambient Occlusion), which makes game worlds look more realistic with better shading and a stronger sense of depth, without putting too much strain on performance. The studio has also made the technology open-source through its Carbon engine framework.
Senior Rendering Engineer Daniel Isheden originally developed CORTAO as an independent project, which later became a full production tool with the studio's support. The team at Fenris Creations has used the technology in EVE Frontier, an upcoming space survival MMO, giving it a chance to perform across vastly different scales: massive open spaces, large-scale battles, megastructures, and enclosed interiors.
CORTAO takes a different approach to screen-space ambient occlusion: it uses information from what's currently visible on screen to represent nearby surfaces as circular occluders, helping calculate how they block ambient light. Testing reportedly shows this approach improves visual accuracy while keeping rendering costs low, with particularly strong results in visually complex scenes.
"Ambient occlusion adds the subtle darkening that occurs where nearby surfaces block light from the environment. It helps objects feel grounded in their surroundings and makes the shape and detail of complex scenes easier to read. CORTAO improves the accuracy and stability of this effect, reducing the dark halos and distracting shifts in shading that can appear around objects as the camera moves.
CORTAO calculates this shading in real time without requiring baked scene data, making it well suited to environments that players continually build and reshape. From the contact between small objects to the overlapping structures of a vast installation, the technique helps preserve a consistent sense of depth as the scene changes."
Here's how CORTAO compares to the existing state of the art, called Ground Truth Ambient Occlusion, according to its developer:
- CORTAO provides a never-before-seen level of physical accuracy rivaling that of brute-force hardware ray tracing, while only relying on screen-space information;
- CORTAO handles depth discontinuities in complex scenes in a more conservative way, avoiding the view-dependent occlusion of GTAO and producing less obvious artifacts when screen space information is limited;
- CORTAO, at the same time, has greatly improved convergence, producing much higher-quality results at lower sample counts even for scenes where GTAO works well, which is especially important for low-end hardware.
Daniel Isheden and Fenris Creations have put together a well-prepared release, giving graphics programmers the freedom to experiment with CORTAO, adapt it to their own projects, and contribute improvements. No AI was involved in the development of CORTAO.
You can find the original CORTAO's source code and documentation here, and the Carbon-optimized version here. For a closer look at how the technique works, including visual comparisons and performance benchmarks, you can visit this page.
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