Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Identity-Expression Ambiguity in 3D Morphable Face Models   3D Morphable Models are a class of generative models commonly used to model
faces. They are typically applied to ill-posed problems such as 3D
reconstruction from 2D data. Several ambiguities in this problem's image
formation process have been studied explicitly. We demonstrate that
non-orthogonality of the variation in identity and expression can cause
identity-expression ambiguity in 3D Morphable Models, and that in practice
expression and identity are far from orthogonal and can explain each other
surprisingly well. Whilst previously reported ambiguities only arise in an
inverse rendering setting, identity-expression ambiguity emerges in the 3D
shape generation process itself. We demonstrate this effect with 3D shapes
directly as well as through an inverse rendering task, and use two popular
models built from high quality 3D scans as well as a model built from a large
collection of 2D images and videos. We explore this issue's implications for
inverse rendering and observe that it cannot be resolved by a purely
statistical prior on identity and expression deformations.

25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex