Ray Tracing Reconstruction via Dynamic Pixel Sampling
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Solution Overview
Problem
Current ray tracing techniques for computer-generated imagery face challenges in achieving high refresh rates and efficient rendering, particularly in real-time applications, due to the need for continuous world simulation updates and the occurrence of visual artifacts like flickering and aliasing.
Innovation Solution
The proposed solution involves a technique that reduces spatial sampling rates by rendering only one pixel out of every 2x2 pixels in each frame, utilizing an increased frame rate, and dynamically varying the pixel ordering based on motion vectors to minimize artifacts. This approach uses a frame generation pipeline that classifies pixels as static or dynamic and applies different composition methods to reduce jagged lines and aliasing effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spatial sampling rate is reduced to render only one pixel out of every 2x2 pixels, then rendering speed increases, but visual quality deteriorates with increased aliasing and jagged lines
Solution Approach 1:
The system performs preliminary classification of pixels as static or dynamic before rendering, and pre-calculates motion vectors for each pixel. This allows the reconstruction pipeline to efficiently determine which pixels need full rendering versus which can be reconstructed from previous frames, optimizing the rendering process before the actual pixel generation occurs.
Solution Approach 2:
The patent transitions from spatial sampling alone to temporal-spatial sampling by incorporating the time dimension. Instead of rendering all pixels every frame, the system renders only a subset of pixels at high temporal resolution and reconstructs other pixels using temporal information from previous frames, effectively moving the sampling problem into the temporal domain.
2Speed
If frame rate is increased to compensate for reduced spatial sampling, then temporal aliasing increases causing flickering artifacts, but maintaining high frame rate increases computational load
Solution Approach 1:
The system uses motion vectors calculated from comparing consecutive frames to provide feedback about pixel movement. This feedback information is used to dynamically adjust the rendering strategy - pixels with significant motion are fully rendered while stationary pixels are reconstructed, allowing the system to maintain high frame rates while minimizing temporal aliasing artifacts.
Solution Approach 2:
The patent implements dynamic pixel classification where pixels are categorized as static or dynamic based on motion analysis. This dynamic approach allows the rendering system to adapt to scene motion characteristics in real-time, rendering only the necessary pixels at each frame while reconstructing others, thereby reducing temporal aliasing without the full computational cost of rendering all pixels at high frame rates.
3Manufacturing precision
If temporal antialiasing with regular subpixel offsets is used, then aliasing is reduced, but device complexity increases due to accumulation buffering requirements
Solution Approach 1:
The patent segments the pixel rendering process by dividing pixels into different categories (static vs. dynamic) and applying different processing strategies to each segment. Static pixels are reconstructed from previous frames while dynamic pixels are fully rendered, allowing the system to reduce aliasing artifacts without requiring complex accumulation buffering for all pixels.
Data Source
AI summary
A method dynamically selects one of a first sampling order and a second sampling order for a ray trace of pixels in a tile where the selection is based on a motion vector for the tile. The sampling order may be a bowtie pattern or an hourglass pattern. Subframes generated based on the sampling order are communicated over a bus along with motion vectors for tiles of the subframes.