Practically unique in its field, the Dolphin emulator is a marvel when it comes to playing Wii and Gamecube games on PC (and Android, too, but with LOTS of reservations). While lately its performance has already been improved enormously, recently a huge jump in quality has been taken with the inclusion of support for DirectX 12, enormously increasing the frame rate of many games compared to DirectX 11 and OpenGL.
The official Dolphin forums display some solid evidence of the improvement to the emulator using both rendering systems. The higher the resolution, the greater the difference, especially above 1080p, which is in itself completely amazing given the original resolutions of the machines being emulated. The following graphics display a comparison of some games using both systems in different conditions.
This addition, initially developed by a member of the user community, has been included in the emulator proper from version 4.0-8933 and practically every few hours a new update with minor changes is being offered on the beta channel. Although the results are obvious, this is still not a final version of the libraries.