Microsoft released Direct3D in 1995, which eventually became the main competitor of OpenGL. Over 50 game developers signed an open letter to Microsoft, released on June 12, 1997, calling on the company to actively support Open GL. On December 17, 1997, Microsoft and SGI initiated the Fahrenheit project, which was a joint effort with the goal of unifying the OpenGL and Direct3D interfaces (and adding a scene-graph API too). In 1998, Hewlett-Packard joined the project. It initially showed some promise of bringing order to the world of interactive 3D computer graphics APIs, but on account of financial constraints at SGI, strategic reasons at Microsoft, and a general lack of industry support, it was abandoned in 1999.