Just as the virtual reality sector is heating up, Oculus VR announced its acquisitions of startup companies Nimble VR and 13th Lab AB.

Oculus, which was acquired by Facebook in a $2 billion deal in March, didn’t divulge the financial details of the acquisitions.

San Francisco-based Nimble VR, which was formerly known as 3Gear Systems, does skeletal hand tracking with tiny, 3-D cameras that can be mounted on top of the Oculus Rift. The company raised funding on Kickstarter and from investors Intel Capital, Crunch Fund, K9 Ventures, Ovo Fund and other backers.

Swedish start-up 13th Lab also uses sophisticated cameras and makes 3-D recreations of various physical environments so that they can be presented in virtual reality. Nordic venture firm Creandum has invested in 13th Lab.

Oculus has also brought aboard special-effects wizard Chris Bregler, a computer-science professor at New York University who has worked on blockbuster Hollywood movies, to become a full-time project engineer, the company said.

With the acquisition, Oculus says the company will be making its virtual worlds more three-dimensional and more responsive to gestures.

Venture investment in virtual-reality startups has been steady since Facebook acquired of Oculus. Startup Survious picked up $2 million and Jaunt raised $28 million, and Virtuix raised $2.7 million this week for its treadmill for immersive virtual reality.