(Adds details from Oculus filing, background on Carmack, Oculus declined to comment)
SAN FRANCISCO, June 25 (Reuters) - Oculus VR, the technology startup that Facebook Inc is buying for $2 billion, has denied improperly using video game publisher ZeniMax Media Inc's trade secrets to create its virtual reality gaming headset.
"There is not a line of ZeniMax code or any of its technology in these or any other Oculus products," Oculus said in documents filed in a Dallas federal court on Wednesday.
"Only after the Facebook acquisition announcement did ZeniMax suddenly begin asserting supposed ownership rights over Oculus VR's technology."
Facebook said in March it would acquire Oculus. The deal has been approved by U.S. antritrust authorities, and is expected to close in coming months.
ZeniMax and its subsidiary, id Software Llc, sued Oculus and co-founder Palmer Luckey in May, claiming that Oculus hired away employees like well-known game programmer John Carmack to "surreptitiously gain further unauthorized access" to intellectual property.
Carmack helped conceive groundbreaking game titles such as "Quake" and "Doom" for id Software before it was acquired by ZeniMax.
In ZeniMax's lawsuit, the publisher alleged that Carmack, chief technology officer at Oculus, may have provided valuable technology to his current employer.
Oculus responded in court documents that Luckey had publicly demonstrated his virtual reality headset prototypes even before making first contact with ZeniMax or Carmack. It also cited an email and online post by Carmack in which he credited Luckey as the inventor of the Rift headset by Oculus.
In 2012, Oculus noted, Carmack asked Luckey to give him a prototype as he was interested in demonstrating his video game software on it at the Eletcronic Entertainment Expo, an annual video game industry convention, according to Oculus' filing.
"Carmack offered Luckey the 'VR Testbed,' a small portion of an existing videogame that Carmack previously had developed to work with head-mounted displays," Oculus said in its filing. A non-disclosure agreement in relation to the video game software was signed by Luckey but never finalized, it said.
As Oculus continued to develop its Rift prototypes, it deisgned the hardware components and developed or licensed its own software, Oculus said. "Oculus VR used no hardware or software technology from ZeniMax," it added in its filing.
Oculus declined to comment and a spokesperson for ZeniMax could not be immediately reached.
(Editing by Jonathan Oatis; Editing by Richard Chang)