Residency Map Descriptors for Partially Resident Texture Memory Management
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Solution Overview
Problem
Graphics processing units (GPUs) face challenges in efficiently managing texture data due to limited dedicated memory, leading to significant overhead in populating texture data, especially when only a small subset is used for rendering, and result in unwanted visual artifacts from non-resident texels returning black color.
Innovation Solution
The implementation of a residency map that indicates the finest level of detail (LOD) populated in a partially resident texture (PRT) resource, allowing for efficient sampling and access to resident texels by clamping requests to less detailed but resident levels, without increasing the size of the texture descriptor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If texture data is stored in dedicated GPU memory, then texture mapping quality is improved, but memory capacity is exceeded and overhead increases
Solution Approach 1:
The texture data is segmented into multiple mipmap levels, where each level represents a different resolution. The system selectively loads and stores only the necessary levels in GPU memory based on current rendering requirements, rather than loading the entire texture hierarchy. This segmentation allows high-quality textures to be used when needed while managing memory capacity constraints.
Solution Approach 2:
The system performs partial action by loading only a subset of mipmap levels into GPU memory rather than all levels. The residency map tracks which levels are currently resident in memory, allowing the system to access only the necessary portion of texture data for current rendering operations, thereby reducing memory overhead while maintaining texture mapping quality for visible elements.
2Quantity of substance
If only a small subset of texture data is used for rendering, then memory usage is reduced, but overhead to populate texture data increases
Solution Approach 1:
The residency map is pre-computed and stored alongside the mipmap levels, indicating in advance which texture levels are likely to be needed. This preliminary action allows the GPU to proactively load the correct mipmap levels into memory before they are actually needed for rendering, reducing the overhead of populating texture data during runtime while maintaining efficient memory usage.
Solution Approach 2:
The residency map enables the texture sampling system to self-manage its own memory population by automatically determining which mipmap levels to load based on the residency information. This self-service mechanism reduces the overhead of external management and optimizes the timing of texture data population without requiring additional manual intervention or complex control logic.
3Ease of operation
If non-resident texels return black color, then memory access is simplified, but visual artifacts occur
Solution Approach 1:
The residency map serves as an intermediary layer between the texture sampling logic and the actual mipmap levels. When a texture sample is requested, the system first consults the residency map to determine which mipmap level contains the required data. This intermediary mechanism guides the sampling process to the correct resident level, preventing black artifacts while maintaining simple memory access patterns through unified sampling semantics.
Solution Approach 2:
The system replaces the traditional mechanical approach of directly sampling mipmap levels with a residency-aware sampling mechanism. Instead of attempting to access potentially non-resident texels and handling errors, the residency map substitution directs samples to appropriate resident levels, eliminating visual artifacts while maintaining the simplicity of texture sampling operations through automated level selection.
Data Source
AI summary
A processor receives a request to access one or more levels of a partially resident texture (PRT) resource. The levels represent a texture at different levels of detail (LOD) and the request includes normalized coordinates indicating a location in the texture. The processor accesses a texture descriptor that includes dimensions of a first level of the levels and one or more offsets between a reference level and one or more second levels that are associated with one or more residency maps that indicate texels that are resident in the PRT resource. The processor translates the normalized coordinates to texel coordinates in the one or more residency maps based on the offset and accesses, in response to the request, the one or more residency maps based on the texel coordinates to determine whether texture data indicated by the normalized coordinates is resident in the PRT resource.