ADAPTIVE SHADING IN A GRAPHICS PROCESSING PIPELINE

• US 20150170408A1
• Filed: 12/13/2013
• Published: 06/18/2015
• Est. Priority Date: 12/13/2013
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: LUM, Eric B., ENDERTON, Eric, MORETON, Henry Packard, HE, Yong, FATAHALIAN, Kayvon
• Granted Patent: US 9,552,667 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G06T 15/00 3D [Three Dimensional] image rendering
• CPC Class Codes: G06T 15/005 General purpose rendering architectures
• CPC Class Codes: G06T 15/80 Shading
• CPC Class Codes: G06T 2210/52 Parallel processing

Abstract

One embodiment of the present invention includes a parallel processing unit (PPU) that performs pixel shading at variable granularities. For effects that vary at a low frequency across a pixel block, a coarse shading unit performs the associated shading operations on a subset of the pixels in the pixel block. By contrast, for effects that vary at a high frequency across the pixel block, fine shading units perform the associated shading operations on each pixel in the pixel block. Because the PPU implements coarse shading units and fine shading units, the PPU may tune the shading rate per-effect based on the frequency of variation across each pixel group. By contrast, conventional PPUs typically compute all effects per-pixel, performing redundant shading operations for low frequency effects. Consequently, to produce similar image quality, the PPU consumes less power and increases the rendering frame rate compared to a conventional PPU.

Claims

1. A computer-implemented method for performing pixel shading operations, the method comprising:

performing a first pixel shading operation on a first pixel to compute a first coarse shading value that is associated with the first pixel;

determining a second coarse shading value that is associated with a second pixel based on the first coarse shading value;

performing a second pixel shading operation on the first pixel to compute a first fine shading value that is associated with the first pixel;

performing the second pixel shading operation on the second pixel to compute a second fine shading value that is associated with the second pixel;

computing a first composite shading value that is associated with the first pixel based on the first coarse shading value and the first fine shading value; and

computing a second composite shading value that is associated with the second pixel based on the second coarse shading value and the second fine shading value.

2. The method of claim 1, wherein determining the second coarse shading value comprises:

performing the first pixel shading operation on a third pixel to compute a third coarse shading value that is associated with the third pixel;

performing an interpolation operation between the first coarse shading value and the third coarse shading value to determine a first estimated value;

determining that a first effect that is associated with the first pixel shading operation exhibits a low frequency variation across a first set of pixels that includes the first pixel, the second pixel, and the third pixel; and

setting the second coarse shading value to equal the first estimated value.

3. The method of claim 2, wherein determining that the first effect exhibits a low frequency variation comprises:

evaluating at least one of the first coarse shading value, the third coarse shading value, and the first estimated value; and

deactivating a first granularity bit that is associated with both the first effect and the first set of pixels.

4. The method of claim 3, wherein the first set of pixels comprises a pixel block that includes a first quad, and deactivating the first granularity bit causes the first quad to be associated with a first warp that includes a first thread that computes the first composite shading value.

5. The method of claim 1, wherein computing the second composite shading value comprises combining the second coarse shading value, the second fine shading value, and a third fine shading value.

6. The method of claim 5, wherein determining the third fine shading value comprises:

performing a third pixel shading operation on the first pixel to determine a fourth coarse shading value that is associated with the first pixel;

determining that a second effect that is associated with the third pixel shading operation exhibits a high frequency variation across a first set of pixels that includes the first pixel and the second pixel; and

performing the third pixel shading operation on the second pixel.

7. The method of claim 6, wherein determining that the second effect exhibits a high frequency variation comprises:

evaluating the fourth coarse shading value; and

activating a first granularity bit that is associated with both the second effect and the first set of pixels.

8. The method of claim 1, wherein a first set of pixels that includes the first pixel and the second pixel comprises a pixel block, and further comprising:

receiving fragments associated with the pixel block; and

determining a plurality of coarse shading pixels that includes the first pixel and does not include the second pixel, wherein the plurality of coarse shading pixels is a subset of the first set of pixels.

9. The method of claim 8, wherein the fragments specify a pixel block visibility mask, and determining the plurality of coarse shading pixels comprises selecting the plurality of coarse shading pixels based on the pixel block visibility mask.

10. A computer-readable storage medium including instructions that, when executed by a processing unit, cause the processing unit to perform pixel shading operations by performing the steps of:

performing a first pixel shading operation on a first pixel to compute a first coarse shading value that is associated with the first pixel;

determining a second coarse shading value that is associated with a second pixel based on the first coarse shading value;

performing a second pixel shading operation on the first pixel to compute a first fine shading value that is associated with the first pixel;

performing the second pixel shading operation on the second pixel to compute a second fine shading value that is associated with the second pixel;

computing a first composite shading value that is associated with the first pixel based on the first coarse shading value and the first fine shading value; and

computing a second composite shading value that is associated with the second pixel based on the second coarse shading value and the second fine shading value.

11. The computer-readable storage medium of claim 10, wherein determining the second coarse shading value comprises:

performing the first pixel shading operation on a third pixel to compute a third coarse shading value that is associated with the third pixel;

performing an interpolation operation between the first coarse shading value and the third coarse shading value to determine a first estimated value;

determining that a first effect that is associated with the first pixel shading operation exhibits a low frequency variation across a first set of pixels that includes the first pixel, the second pixel, and the third pixel; and

setting the second coarse shading value to equal the first estimated value.

12. The computer-readable storage medium of claim 11, wherein determining that the first effect exhibits a low frequency variation comprises:

evaluating at least one of the first coarse shading value, the third coarse shading value, and the first estimated value; and

deactivating a first granularity bit that is associated with both the first effect and the first set of pixels.

13. The computer-readable storage medium of claim 12, wherein the first set of pixels comprises a pixel block that includes a first quad, and deactivating the first granularity bit causes the first quad to be associated with a first warp that includes a first thread that computes the first composite shading value.

14. The computer-readable storage medium of claim 10, wherein computing the second composite shading value comprises combining the second coarse shading value, the second fine shading value, and a third fine shading value.

15. The computer-readable storage medium of claim 14, wherein determining the third fine shading value comprises:

performing a third pixel shading operation on the first pixel to determine a fourth coarse shading value that is associated with the first pixel;

determining that a second effect that is associated with the third pixel shading operation exhibits a high frequency variation across a first set of pixels that includes the first pixel and the second pixel; and

performing the third pixel shading operation on the second pixel.

16. The computer-readable storage medium of claim 15, wherein determining that the second effect exhibits a high frequency variation comprises:

evaluating the fourth coarse shading value; and

activating a first granularity bit that is associated with both the second effect and the first set of pixels.

17. The computer-readable storage medium of claim 10, wherein a first set of pixels that includes the first pixel and the second pixel comprises a pixel block, and further comprising:

receiving fragments associated with the pixel block; and

determining a plurality of coarse shading pixels that includes the first pixel and does not include the second pixel, wherein the plurality of coarse shading pixels is a subset of the first set of pixels.

18. The computer-readable storage medium of claim 17, wherein the fragments specify a pixel block visibility mask, and determining the plurality of coarse shading pixels comprises selecting the plurality of coarse shading pixels based on the pixel block visibility mask.

19. A system configured to perform pixel shading operations, the system comprising:

a pixel shading subsystem configured to;

perform a first pixel shading operation on a first pixel to compute a first coarse shading value that is associated with the first pixel;

determine a second coarse shading value that is associated with a second pixel based on the first coarse shading value;

perform a second pixel shading operation on the first pixel to compute a first fine shading value that is associated with the first pixel;

perform the second pixel shading operation on the second pixel to compute a second fine shading value that is associated with the second pixel;

compute a first composite shading value that is associated with the first pixel based on the first coarse shading value and the first fine shading value; and

compute a second composite shading value that is associated with the second pixel based on the second coarse shading value and the second fine shading value.

20. The system of claim 19, wherein the pixel shading subsystem is configured to determine the second coarse shading value by:

performing the first pixel shading operation on a third pixel to compute a third coarse shading value that is associated with the third pixel;

performing an interpolation operation between the first coarse shading value and the third coarse shading value to determine a first estimated value;

determining that a first effect that is associated with the first pixel shading operation exhibits a low frequency variation across a first set of pixels that includes the first pixel, the second pixel, and the third pixel; and

setting the second coarse shading value to equal the first estimated value.

21. A computer-implemented method for performing pixel shading operations, the method comprising:

performing a first pixel shading operation on a first pixel to compute a first coarse shading value that is associated with the first pixel;

performing the first pixel shading operation on a second pixel to compute a second coarse shading value that is associated with the second pixel;

performing an interpolation operation between the first coarse shading value and the second coarse shading value to determine a third coarse shading value that is associated with a third pixel; and

outputting at least the third coarse shading value as a final pixel value for display.