As of this week, there's also Unity 4.0 for Linux and other game engines coming to Linux, but for the top-spot it's largely a battle between Unigine and Source. Valve at the same time is also working on a new game engine to succeed Source. While the Unigine Engine isn't as widely adopted as the Source Engine nor is the company as well-staffed with as many resources as Valve Software, the Russian-based company is continuing to move forward. A new round of improvements to the Unigine Engine were shared this morning.
One of the big improvements to the Unigine Engine with the latest revision is bettering SSDO. The Screen Space Directional Occlusion (SSDO) within the Unigine Engine has been "tremendously improved" to avoid artifacts and be more physically correct and no more noise for real-time global illumination. At the end of this article are some screenshots with the new Unigine Engine rendering enhancements.
A new import plug-in has also been added to the Unigine development stack for handling COLLADA with its .DAE files. This includes support for mesh geometry, full-node hierarchy, materials, animation, lights, and camera.
Some of the new Unigine renderer improvements include an HDR lens flare, 16x anti-aliasing mode, faster calculation of environment lighting for grass, support for array material parameters, RGB10A2 texture format support for Intel CPUs, and shades of light scattering now blend smoothly rather than color-banding.
devlog. To much dismay, the Unigine Valley tech demo is still not publicly available...