implementations from Nvidia, AMD, and Intel. Later AMD donated Mantle to Khronos Group, the API was renamed Vulkan and now this is the current cross-platform API dedicated to reduce driver overhead, while better distributing work among multiple CPU and GPU cores, using a unified management of compute kernels and graphical shaders. During the presentation, apitest was introduced. It is a new tool for microbenchmarking specific solutions for given problems emphasizing exploration of fast paths in current APIs. Both OpenGL 4.x and Direct3D 11 are supported. Gathered results showed that modern OpenGL can be many times faster than Direct3D 11. Structure OpenGL, originally designed for then-powerful SGI workstations, includes many features, like stereo rendering and the imaging subset, that were generally considered of limited use for games, although stereoscopic gaming has drawn more interest with the development of consumer-level 3D displays. The API as a whole contains about 250 calls, but only a subset of perhaps 100 are useful for game development. However, no official gaming-specific subset was ever defined. MiniGL, released by 3Dfx as a stopgap measure to support GLQuake, might have served as a starting point, but additional features like stencil were soon adopted by games, and support for the full OpenGL standard continued. Today, workstations and consumer machines use the same architectures and operating systems, and so modern versions of the OpenGL standard still include these features, although only special workstation-class video cards accelerate them. Extensions The OpenGL extension mechanism is probably the most heavily disputed difference between the two APIs. OpenGL includes a mechanism where any driver can advertise its own extensions to the API, thus introducing new functions such as blend modes, new ways to transfer data to GPUs, or different texture wrapping parameters. This allows new functions to be exposed quickly, but can lead to confusion if different vendors implement similar extensions with different APIs. Many of these extensions are periodically standardized by the OpenGL Architecture Review Board (ARB), and some are made a core part of future OpenGL revisions. On the other hand, Direct3D is specified by one vendor only (Microsoft), leading to a more consistent API, but denying access to vendor-specific features. NVIDIA's UltraShadow technology, for instance, is not available in the stock Direct3D APIs at the time of writing. Direct3D does support texture format extensions (via FourCC). These were once little-known and rarely used, but are now used for S3 Texture Compression.