Volumetric Rendering via Combined Transmissivity and CDF Sampling
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Solution Overview
Problem
Rendering multiple volumetric objects in computer animation is inefficient due to memory constraints and the need for re-rendering when light sources change, especially in GPU-based systems, where volumes can overlap and have varying transmissivity and scattering characteristics.
Innovation Solution
Determining individual transmissivity functions for each volume, combining them into a combined transmissivity function, and generating a cumulative density function (CDF) to efficiently sample points along a ray, allowing for interactive lighting adjustments without full re-rendering and reducing memory requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all volumes are kept in memory simultaneously for rendering, then rendering accuracy is maintained, but memory usage and bandwidth requirements increase significantly
Solution Approach 1:
The patent segments the rendering process into multiple passes: a first pass that processes volumes and generates intermediate data, and a second pass that uses this intermediate data for final rendering. This segmentation allows memory-intensive operations to be distributed across passes rather than requiring all volume data to be held in memory simultaneously, thus reducing peak memory usage while maintaining rendering accuracy.
Solution Approach 2:
The patent performs preliminary processing in a first pass to generate intermediate representation data before the actual rendering occurs. By pre-computing and storing essential volume information in an optimized format during the first pass, the system reduces the memory burden during the second rendering pass, as only the intermediate data needs to be retained rather than complete volume datasets.
2Reliability
If the scene is fully re-rendered when light sources are modified, then rendering accuracy is maintained, but rendering time increases
Solution Approach 1:
The patent separates the rendering pipeline into distinct segments: geometry and volume processing (first pass) and lighting-dependent rendering (second pass). When light sources are modified, only the second pass needs to be re-executed while reusing the intermediate data from the first pass. This segmentation allows selective re-rendering of only the affected portion, maintaining accuracy while reducing the time penalty compared to full scene re-rendering.
Solution Approach 2:
The first pass performs preliminary processing to create lighting-independent intermediate representation data that can be reused across multiple lighting configurations. This preliminary action separates geometry processing from lighting computation, enabling efficient updates when lighting changes occur without requiring recalculation of the entire scene, thus reducing rendering time while preserving accuracy.
3Manufacturing precision
If detailed volume rendering is performed, then image quality is improved, but computational complexity and resource requirements increase
Solution Approach 1:
The patent divides the complex volume rendering task into two separate passes, each handling specific aspects of the computation. The first pass focuses on geometry processing and intermediate data generation, while the second pass handles lighting and final image synthesis. This segmentation reduces the computational complexity of each individual pass compared to performing all operations in a single complex pass, while maintaining the ability to produce high-quality detailed renders.
Data Source
AI summary
Embodiments of the invention are directed to rendering scenes comprising one or more volumes viewed along a ray from a virtual camera. In order to render the one or more volumes, embodiments may first determine individual transmissivity functions for the one or more volumes. The individual transmissivity functions may be combined into a combined transmissivity function for the scene. The combined transmissivity function may be used to generate a cumulative density function (CDF) for the scene. The CDF may be sampled in order to determine a plurality of points along the ray. A contribution to a pixel may be determined for each sampled point. The contributions associated with the sampled points may be combined to determine a combined contribution to the pixel.