Apparatus and method for virtual reality

A data processing method comprising:

• receiving tracking data indicative of at least one of a tracked position and a tracked orientation for a head-mountable display (HMD);
• generating, by image processing circuitry, a sequence of image frames for display in dependence upon the tracking data for the HMD, in which the step of generating comprises generating the sequence of image frames with viewpoints that change according to changes in at least one of the tracked position and the tracked orientation of the HMD indicated by the tracking data for the HMD;
• detecting image features in the sequence of image frames generated by the image processing circuitry by detecting at least an image feature included in a first image frame generated for display at a first time with a first viewpoint and detecting a corresponding image feature included in a second image frame generated for display at a second time with a second viewpoint different from the first viewpoint;
• calculating a difference between the image feature in the first image frame and the corresponding image feature in the second image frame;
• generating difference data indicative of a difference between the first viewpoint for the first image frame and the second viewpoint for the second image frame in dependence upon the difference between the image feature in the first image frame and the corresponding image feature in the second image frame;
• and
• generating output data in dependence upon a difference between the difference data and the tracking data used to generate the first and second image frames, the output data being indicative of discrepancy for the difference between the first viewpoint and the second viewpoint and a difference between at least one of the tracked position and the tracked orientation of the HMD indicated by the tracking data used to generate the first and second image frames.

Computer software which, when executed by a computer, causes the computer to carry out a method comprising:

• receiving tracking data indicative of at least one of a tracked position and a tracked orientation for a head-mountable display (HMD);
• generating, by image processing circuitry, a sequence of imageimages frames for display in dependence upon the tracking data for the HMD, in which the step of generating comprises generating the sequence of image frames with viewpoints that change according to changes in at least one of the tracked position and the tracked orientation of the HMD indicated by the tracking data for the HMD;
• detecting image features in the sequence of image frames generated by the image processing circuitry by detecting at least an image feature included in a first image frame generated for display at a first time with a first viewpoint and detecting a corresponding image feature included in a second image frame generated for display at a second time with a second viewpoint different from the first viewpoint;
• calculating a difference between the image feature in the first image frame and the corresponding image feature in the second image frame;
• generating difference data indicative of a difference between the first viewpoint for the first image frame and the second viewpoint for the second image frame in dependence upon the difference between the image feature in the first image frame and the corresponding image feature in the second image frame;
• and
• generating output data in dependence upon a difference between the difference data and the tracking data used to generate the first and second image frames, the output data being indicative of discrepancy for the difference between the first viewpoint and the second viewpoint and a difference between at least one of the tracked position and the tracked orientation of the HMD indicated by the tracking data used to generate the first and second image frames.