MFA-DVR: Direct Volume Rendering of MFA Models
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3D volume rendering is widely used to reveal insightful intrinsic patterns of volumetric datasets across many domains. However, the complex structures and varying scales of datasets make generating a high-quality volume rendering results efficiently a challenging task. Multivariate functional approximation (MFA) is a new data model that addresses some of the key challenges of volume visualization. MFA provides high-order evaluation of values and derivatives anywhere in the spatial domain, mitigating the artifacts caused by the zero- or first-order interpolation commonly implemented in existing volume visualization algorithms. MFA's compact representation improves the space complexity for large-scale volumetric data visualization, while its uniform representation of both structured and unstructured data allows the same ray casting algorithm to be used for a variety of input data types. In this paper, we present MFA-DVR, the first direct volume rendering pipeline utilizing the MFA model, for both structured and unstructured volumetric datasets. We demonstrate improved rendering quality using MFA-DVR on both synthetic and real datasets through a comparative study with raw and compressed data. We show that MFA-DVR not only generates more faithful volume rendering results with less memory footprint, but also performs faster than traditional algorithms when rendering unstructured datasets. MFA-DVR is implemented in the existing volume rendering pipeline of the Visualization Toolkit (VTK) in order to be accessible by the scientific visualization community.
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