Facebook CEO Mark Zuckerberg has defended his virtual reality company Oculus in a lawsuit filed against him by ZeniMax Media. 

Zuckerberg testified confidently in court denying ZeniMax allegations. "The idea that Oculus Technology is from someone else's idea is wrong," he said.

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ZeniMax, the known creator of video games "Doom," "Fallout," and "Quake" is accusing Oculus of stealing the intellectual property initiated by its former employee, John Carmack. The court hearing started last week in Dallas.

The Oculus Rift virtual reality technology headset and headphones costs $599. Facebook spent about $3 billion to establish Oculus, according to the New York Times.

Zuckerberg hired Carmack from ZeniMax to lead the technology department of Oculus in August 2013. Carmack's affiliation with Oculus triggered Zenimax to file a lawsuit against Oculus. ZeniMax claims that Oculus was developed through its research and facilities when Carmack was still working for the company.

Facebook introduced Oculus in March 2014.  Amin Zoufounoun, Facebook's vice president for corporate development, conducted his legal review of the business deal between Facebook and Oculus.

Carmack is leading the $2 billion lawsuit against Oculus. Palmer Luckey, who worked with ZeniMax and is one of the founders of Oculus, as well as Brendan Iribe, former Oculus CEO, also testify in the hearing.

The trial was attended by legal experts representing Oculus and ZeniMax. Media personalities from prominent news organizations were also present in the crowded courtroom.

The Oculus lawsuit is the second major case that Zuckerberg is facing. The first one was filed by some of his Harvard classmates who accused him of stealing the idea of creating Facebook. That case was settled privately.

Zuckerberg appeared in the courtroom with a formal suit instead of his usual hoodie shirt outfit.