The Valve/Oculus Layered Compositors (Magic Glue for VR)

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UPDATE: The speculation didn’t last long. Valve has just released their OpenVR SDK which includes documentation for the Compositor. The actual implementation differs in some interesting ways, but the Use and Features section, below, is still a good summary of what Valve and Oculus are trying to achieve here. More details are at the end of this article.

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INTRODUCTION

In March, Valve released a new concept into SteamVR called the VR Compositor. Like everything else at this point, the specification is not yet public. (So insert the standard speculative disclaimers here. If I flubbed something, please be forgiving, but let me know.) It shouldn’t be too hard for us to tease together what its function and purpose might be.

VR Compositor:

• This is a new component of SteamVR that simplifies the process of adding VR support to an application.
• Continues to draw an environment even if the application hangs.
• Simplifies handing off from one application to another without full screen context changes by owning the window on the headset.

-Programmer Joe (Valve)

Let’s break that down a bit. The compositor grabs the VR display, owns it, and continues running. When a compositor-aware application wants to use the HMD, it goes to the compositor to request access to the HMD. The compositor hands a buffer to the application and tells the application to render into that buffer.