Sparse Volumetric Ray Casting With Occupancy-Based Empty Space Removal
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Solution Overview
Problem
Current computer systems face challenges in processing large 3D data sets efficiently, particularly in augmented and mixed reality applications, due to constraints in memory, processing resources, and power, which can lead to latency issues and motion sickness in users.
Innovation Solution
The implementation of a sparse volumetric data structure that tags voxels as occupied or empty, allowing for the removal of empty space and utilizing a sparse sexaquaternary tree format, which reduces storage requirements and enables faster processing and transmission of data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dense volumetric data structures are used to represent 3D space in augmented and mixed reality systems, then complete spatial coverage and accuracy are achieved, but memory consumption and processing time increase significantly
Solution Approach 1:
The patent applies local quality by differentiating between occupied and empty voxels, applying different storage representations based on local spatial characteristics. Occupied voxels (containing geometry) are stored with full detail while empty voxels are represented more compactly, allowing high spatial accuracy where needed while reducing overall memory consumption in large 3D spaces.
Solution Approach 2:
The patent implements a porous data structure approach by creating a sparse volumetric representation that allows 'empty space' to be represented differently from occupied space. This enables the system to maintain the volumetric grid structure for accurate spatial queries while having 'holes' or empty regions that consume minimal storage resources, analogous to porous materials having void spaces.
2Measurement precision
If complete volumetric data is processed in real-time for augmented and mixed reality rendering, then rendering accuracy is maintained, but processing speed and latency are degraded
Solution Approach 1:
The patent extracts and removes empty voxels from the processing pipeline entirely. By identifying voxels that contain no geometric data and excluding them from storage and processing operations, the system maintains rendering accuracy for occupied regions while dramatically reducing the total number of operations required, thus improving processing speed and reducing latency.
Solution Approach 2:
The patent applies partial action by processing only the necessary subset of volumetric data (occupied voxels) rather than the complete volumetric grid. This selective processing approach performs exactly what is needed for accurate rendering without the excessive computation required to handle all voxels in the 3D space, including empty ones.
3Loss of information
If traditional volumetric data structures are used, then comprehensive spatial information is stored, but data transmission bandwidth and storage requirements increase
Solution Approach 1:
The patent changes the storage parameter for voxels based on their occupancy state. Occupied voxels are stored with their geometric data using efficient encodings (such as run-length encoding or compressed formats), while empty voxels are represented by a simple absence marker or compressed reference, dramatically reducing the average bytes per voxel while maintaining complete spatial information where geometry exists.
Data Source
AI summary
A ray is cast into a volume described by a volumetric data structure, which describes the volume at a plurality of levels of detail. A first entry in the volumetric data structure includes a first set of bits representing voxels at a lowest one of the plurality of levels of detail, and values of the first set of bits indicate whether a corresponding one of the voxels is at least partially occupied by respective geometry. A set of second entries in the volumetric data structure describe voxels at a second level of detail, which represent subvolumes of the voxels at the first lowest level of detail. The ray is determined to pass through a particular subset of the voxels at the first level of detail and at least a particular one of the particular subset of voxels is determined to be occupied by geometry.