C Specification

The xrBeginSession function is defined as:

// Provided by XR_VERSION_1_0
XrResult xrBeginSession(
    XrSession                                   session,
    const XrSessionBeginInfo*                   beginInfo);

Parameters

Parameter Descriptions

Description

When the application receives XrEventDataSessionStateChanged event with the XR_SESSION_STATE_READY state, the application should then call xrBeginSession to start rendering frames for display to the user.

After this function successfully returns, the session is considered to be running. The application should then start its frame loop consisting of some sequence of xrWaitFrame/xrBeginFrame/xrEndFrame calls.

If the session is already running when the application calls xrBeginSession, the runtime must return error XR_ERROR_SESSION_RUNNING. If the session is not running when the application calls xrBeginSession, but the session is not yet in the XR_SESSION_STATE_READY state, the runtime must return error XR_ERROR_SESSION_NOT_READY.

Note that a runtime may decide not to show the user any given frame from a session at any time, for example if the user has switched to a different application’s running session. The application should check whether xrWaitFrame returns XrFrameState::shouldRender set to true before rendering a given frame to determine whether that frame will be visible to the user.

Runtime session frame state must start in a reset state when a session transitions to running so that no state is carried over from when the same session was previously running. Frame state in this context includes xrWaitFrame, xrBeginFrame, and xrEndFrame call order enforcement.

If XrSessionBeginInfo::primaryViewConfigurationType in beginInfo is not supported by the XrSystemId used to create the session, the runtime must return XR_ERROR_VIEW_CONFIGURATION_TYPE_UNSUPPORTED.

Valid Usage (Implicit)
Return Codes
On success, this command returns

  • XR_SUCCESS

  • XR_SESSION_LOSS_PENDING

On failure, this command returns

  • XR_ERROR_VALIDATION_FAILURE

  • XR_ERROR_RUNTIME_FAILURE

  • XR_ERROR_HANDLE_INVALID

  • XR_ERROR_INSTANCE_LOST

  • XR_ERROR_SESSION_LOST

  • XR_ERROR_VIEW_CONFIGURATION_TYPE_UNSUPPORTED

  • XR_ERROR_SESSION_RUNNING

  • XR_ERROR_SESSION_NOT_READY

See Also

XR_VERSION_1_0, XrSession, XrSessionBeginInfo, xrCreateSession, xrDestroySession, xrEndSession

Document Notes

For more information, see the OpenXR Specification

This page is extracted from the OpenXR Specification. Fixes and changes should be made to the Specification, not directly.

Copyright

Copyright 2014-2024, The Khronos Group Inc.

This work is licensed under a Creative Commons Attribution 4.0 International License.