Tile-Buffer Shading Rate Control for VRS and SSAA Integration
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Solution Overview
Problem
Existing 3D graphics processing pipelines face inefficiencies in pixel shading due to redundant operations when performing rasterization and pixel shading at the same resolution, particularly for triangles with fixed colors or low frequency color changes, and integrating variable rate shading (VRS) with super sample anti-aliasing (SSAA) can result in undefined results.
Innovation Solution
A technique is introduced where rasterization is performed at a normal resolution, with quads accumulated into a tile buffer, and shading rates are determined for the tile buffer contents, allowing for down-sampling or up-sampling based on sub-sampling or super-sampling rates to optimize pixel shader workload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rasterization and pixel shading are performed at the same resolution, then coverage accuracy is maintained, but processing efficiency deteriorates due to redundant pixel shader operations
Solution Approach 1:
The patent segments the rendering process into two distinct resolution stages: rasterization at one resolution and pixel shading at a different resolution. This allows the system to perform coverage determination at a coarser level while reserving fine-detail shading for only those pixels that actually require it, thereby reducing redundant pixel shader operations while maintaining necessary coverage accuracy.
Solution Approach 2:
The patent applies different quality levels to different regions of the image by determining pixel shading resolution on a per-pixel or per-region basis. Pixels or regions that require high precision (such as those with complex geometry or important visual features) are shaded at full resolution, while other areas use lower resolution shading, optimizing the balance between processing efficiency and visual quality.
2Productivity
If variable rate shading is integrated with super sample anti-aliasing, then processing efficiency improves by reducing redundant calculations, but result reliability deteriorates due to undefined behavior
Solution Approach 1:
The patent performs preliminary determination of pixel shading resolution before executing the pixel shader. By pre-calculating which pixels require high-resolution shading and which can use lower resolution, the system avoids undefined behavior in VRS-SSAA integration while maintaining processing efficiency. This preliminary action establishes a clear execution order that prevents conflicts between the two techniques.
Solution Approach 2:
The patent dynamically adjusts the pixel shading resolution based on local image characteristics and anti-aliasing requirements. Rather than using a fixed resolution for all pixels, the system varies the shading rate dynamically across different regions, allowing optimal integration of VRS and SSAA by adapting to local needs rather than applying rigid rules that could lead to undefined behavior.
Data Source
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AI summary
A technique for performing rasterization and pixel shading with decoupled resolution is provided herein. The technique involves performing rasterization as normal to generate quads. The quads are accumulated into a tile buffer. A shading rate is determined for the contents of the tile buffer. If the shading rate is a sub-sampling shading rate, then the quads in the tile buffer are down-sampled, which reduces the amount of work to be performed by a pixel shader. The shaded down-sampled quads are then restored to the resolution of the render target. If the shading rate is a super-sampling shading rate, then the quads in the tile buffer are up-sampled. The results of the shaded down-sampled or up-sampled quads are written to the render target.