Coarse Pixel Shading Merge for Redundant Fragment Reduction
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Solution Overview
Problem
Coarse pixel shading techniques are limited by redundant pixel shading executions due to factors like scene depth complexity, partially covered pixels, and quad fragment-based scheduling, especially in modern rendering workloads with small triangles, leading to inefficiencies and potential artifacts.
Innovation Solution
A clustering stage before coarse pixel shading merges coarse quad-fragments of different triangles if they belong to the same surface, using a coverage-weighted average of vertex attributes to reduce redundant shading computations and minimize artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If coarse pixel shading merges blocks of quad-fragments from the same primitive, then shading costs are reduced, but redundant pixel shading executions occur due to scene depth complexity and partially covered pixels
Solution Approach 1:
The patent merges coarse pixel shading quads from multiple different primitives into a single shading operation when they correspond to the same coarse pixels on screen. This extends the traditional merging approach (which only merged quads from the same primitive) to combine quads across multiple primitives, thereby reducing redundant shading executions and improving rendering efficiency
Solution Approach 2:
The patent creates a universal merging mechanism that handles quads from any primitive regardless of their source, as long as they map to the same screen coordinates. This multi-functional approach allows the same merging logic to handle various rendering scenarios including depth complexity and partial coverage cases, making the system more adaptable and efficient
2Device complexity
If coarse pixel shading works within a single rasterized primitive, then merging is simpler, but benefits are amortized in modern rendering workloads with small triangles
Solution Approach 1:
The patent combines multiple quads from different primitives into a single shading operation by checking if they correspond to the same coarse pixels on screen. This merging approach allows the system to achieve better shading efficiency even with small triangles by accumulating enough quads across multiple primitives to form complete shading blocks
Solution Approach 2:
The patent performs preliminary grouping and identification of quads that should be merged before the actual shading operation. By pre-organizing quads from multiple primitives into mergeable groups based on their screen coordinates, the system prepares the data structure in advance to maximize shading efficiency without adding complexity to the core shading logic
3Reliability
If multiple primitives cover the same pixel, then more complete coverage is achieved, but redundant shading executions increase
Solution Approach 1:
The patent merges shading quads from multiple primitives that cover the same screen pixels into a single shading operation. This ensures complete pixel coverage while eliminating redundant shading executions by processing all quads mapping to the same coarse pixels in one unified shading pass
Solution Approach 2:
The patent uses a screen-coordinate-based indexing system that acts as a copy mechanism to identify and group quads from different primitives that correspond to the same location on screen. This indexing approach allows the system to efficiently match and merge quads without requiring complex geometric calculations, reducing shading executions while maintaining complete coverage
Data Source
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AI summary
The disclosure relates to a method that includes interpolating vertex attributes at coarse pixel centers of two primitives, computing input attributes as a coverage weighted average of the interpolated vertex attributes for the two primitives, merging the two primitives, and performing coarse pixel shading using the merged two primitives. A corresponding apparatus is disclosed.