Low latency distortion unit for head mounted displays

1. A graphics processing system for a head-mounted display (HMD) comprising:

a graphics processing unit (GPU) configured to generate pixel data rendered with one or more standard projections, such that the rendered pixel data is suitable for display on a planar, non-HMD display; and

a hardware distortion unit (HDU) separate from the GPU and configured to:

perform a predefined fixed set of functions to transform the pixel data generated by the GPU into distorted pixel data which is suitable for display on the head mounted display, and

output the distorted pixel data for display on the HMD;

wherein the transformation performed by the predefined fixed set of functions is dependent upon input data comprising updated head position and/or orientation data.

2. The graphics processing system according to claim 1 , wherein the graphics processing unit by use of the distinct HDU does not perform a pass through the GPU for the purposes of transforming the pixel data generated by the GPU into distorted pixel data.

3. The graphics processing system according to claim 1 , wherein the hardware distortion unit outputs distorted pixels with computed pixel values and in the required order for direct display on the head mounted display.

4. The graphics processing system according to claim 1 , wherein the hardware distortion unit comprises:

a mapping unit comprising hardware logic arranged to perform a mapping of the pixel data to introduce distortion; and

a transformation unit configured to adjust the mapping performed by the mapping unit in response to input data, and wherein the input data comprises at least one of updated head position; orientation data and a transformational matrix.

5. The graphics processing system according to claim 4 , wherein the hardware distortion unit further comprises:

an input configured to receive pixel data generated by the graphics processing unit; and

an output configured to output distorted pixel data generated, at least in part, by the mapping unit.

6. The graphics processing system according to claim 5 , wherein the output is configured to transmit the distorted pixel data in raster order to the HMD.

7. The graphics processing system according to claim 1 , wherein the hardware distortion unit further comprises a filter unit comprising hardware logic arranged to perform filtering of pixel data output by the mapping unit and provide the distorted pixel data to the output.

8. The graphics processing system according to claim 1 , wherein the hardware distortion unit further comprises one or more look-up tables arranged to store mapping data and wherein the hardware logic in the mapping unit is arranged to access the mapping data and to perform the mapping using the mapping data.

9. The graphics processing system according to claim 1 , wherein the distortion introduced is dependent upon an optical arrangement in the HMD.

10. The graphics processing system according to claim 1 , wherein the mapping performed by the mapping unit is a texture mapping.

11. The graphics processing system according to claim 1 , wherein the hardware distortion unit is configured to output the distorted pixel data with computed pixel values and in the required order for direct display on the HMD.

12. The graphics processing system according to claim 1 , further comprising a frame buffer memory wherein the graphics processing unit is arranged to output the pixel data to the frame buffer memory and the hardware distortion unit is arranged to read the pixel data from the frame buffer memory.

13. A head-mounted display comprising the graphics processing system according to claim 1 .

14. A method of generating pixel data for a head-mounted display (HMD), the method comprising:

generating, in a graphics processing unit (GPU) in a HMD, pixel data rendered with one or more standard projections such that the rendered pixel data is suitable for display on a planar, non-HMD display;

performing a predefined fixed set of functions to transform, in a hardware distortion unit (HDU) separate from the GPU, the pixel data generated by the GPU into distorted pixel data which is suitable for display on the HMD; and

outputting the distorted pixel data for display on the HMD;

wherein the transformation performed by the predefined fixed set of functions is dependent upon input data comprising updated head position and/or orientation data.

15. The method according to claim 14 , wherein the graphics processing unit by using the distinct HDU does not perform a pass through the GPU for the purposes of transforming the pixel data generated by the GPU into distorted pixel data.

16. The method according to claim 14 , wherein transforming the pixel data generated by the GPU into distorted pixel data comprises:

performing a mapping of the pixel data to introduce distortion and generate the distorted pixel data, wherein the mapping is adjusted in response to input data; and wherein the input data comprises at least one of updated head position, orientation data, and a transformational matrix.

17. A graphics processing system configured to perform the method as set forth in claim 14 .

18. The graphics processing system of claim 17 wherein the graphics processing system is embodied in hardware on an integrated circuit.

19. A non-transitory computer readable storage medium having stored thereon computer readable code configured to cause the method of claim 14 to be performed when the code is run on at least one processor.