The Mixture Graph - A Data Structure for Compressing, Rendering, and Querying Segmentation Histograms

Khaled Al-Thelaya, Marco Agus, Jens Schneider

External link (DOI)
View presentation:2020-10-30T17:15:00ZGMT-0600Change your timezone on the schedule page
2020-10-30T17:15:00Z
Exemplar figure
Volumes storing nominal segment IDs such as they arise in neuroscience or material science (top) pose a challenge for direct rendering. The Mixture Graph addresses this challenge by providing a new data structure that allows for direct, GPU-based rendering of such data. It provides interactive transfer function updates across all levels of a mipmap (bottom). In addition, the data structure naturally supports volume lighting, empty space skipping, as well as accelerated computing of segment histograms across 3D regions of interest.
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Keywords

Segmented Volumes, Data Structures, Sparse Data

Abstract

In this paper, we present a novel data structure, called the Mixture Graph. This data structure allows us to compress, render, and query segmentation histograms. Such histograms arise when building a mipmap of a volume containing segmentation IDs. Each voxel in the histogram mipmap contains a convex combination (mixture) of segmentation IDs. Each mixture represents the distribution of IDs in the respective voxel's children. Our method factorizes these mixtures into a series of linear interpolations between exactly two segmentation IDs. The result is represented as a directed acyclic graph (DAG) whose nodes are topologically ordered. Pruning replicate nodes in the tree followed by compression allows us to store the resulting data structure efficiently. During rendering, transfer functions are propagated from sources (leafs) through the DAG to allow for efficient, pre-filtered rendering at interactive frame rates. Assembly of histogram contributions across the footprint of a given volume allows us to efficiently query partial histograms, achieving up to 178x speed-up over naive parallelized range queries. Additionally, we apply the Mixture Graph to compute correctly pre-filtered volume lighting and to interactively explore segments based on shape, geometry, and orientation using multi-dimensional transfer functions.