Ground plane adjustment in a virtual reality environment

A head mounted display (HMD) device operable by a user in a physical environment having a real world floor, comprising:

• one or more processors;
• a display for rendering a virtual reality environment to the user, the virtual reality environment including a ground plane with different elevations at different locations within the virtual reality environment;
• and
• one or more memory devices storing computer-readable instructions which, when executed by the one or more processors, perform a method comprising the steps of:
• generating surface reconstruction data using a depth sensor or camera system,
• using the surface reconstruction data, determining a position of the user's head within the physical environment,
• operating the HMD device to render the virtual reality environment on the display to align a ground plane of the virtual reality environment with the real world floor based on the determined height, wherein the alignment is performed dynamically based on a time-based metric, and
• subjecting the dynamic alignment of the virtual ground plane based on the time-based metric to smoothing, wherein the dynamic alignment is performed according to the determined position of the user's head within the physical environment.

One or more computer readable memory devices not consisting of propagating signals storing computer-executable instructions for rendering a virtual reality environment having variable virtual elevations on a head mounted display (HMD) device located in a physical space having a floor, the method comprising the steps of:

• using one or more sensors in the HMD device to dynamically generate and update a model of the physical space as the user traverses the virtual reality environment;
• determining a position of the user's head within the physical space using the model;
• displaying a portion of the virtual reality environment in a display of the HMD device using a succession of video frames;
• and
• using the determined position, matching an elevation of a ground plane of the virtual reality environment with the floor of the physical space in one or more frames of video,
• wherein the matching is performed on a frame-by-frame basis or a group of frames basis according to the determined position of the user's head within the physical space.