Editing PHIGS (section)

== The rise of OpenGL and the decline of PHIGS ==
[[OpenGL]], unlike PHIGS, was an [[Immediate mode (computer graphics)|immediate-mode]] rendering system with no "state"; once an object is sent to a view to be rendered it essentially disappears. Changes to the model had to be re-sent into the system and re-rendered, a dramatically different programming mindset. For simple projects, PHIGS was considerably easier to use and work with.

However, OpenGL's "low-level" API allowed the programmer to make dramatic improvements in rendering performance by first examining the data on the [[Central processing unit|CPU]]-side before trying to send it over the bus to the graphics engine. For instance, the programmer could "cull" the objects by examining which objects were actually visible in the scene, and sending only those objects that would actually end up on the screen. This was kept private in PHIGS, making it much more difficult to tune performance, but enabling tuning to happen "for free" within the PHIGS implementation.

Given the low performance systems of the era and the need for high-performance rendering, OpenGL was generally considered to be much more "powerful" for 3D programming. PHIGS fell into disuse. Version 6.0 of the PEX protocol was designed to support other 3D programming models as well, but did not regain popularity. PEX was mostly removed from [[XFree86]] 4.2.x (2002) and finally removed from the X Window System altogether in X11R6.7.0 (April 2004).<ref>{{cite web|url=https://lwn.net/Articles/79302/|title=X.Org Foundation releases X Window System X11R6.7}}</ref>