The theory of illuminance flow estimation by structure tensors is generalized for oblique viewing of anisotropic texture. An added benefit is that the theory predicts the behavior of unsupervised illuminant tilt estimators. The previous theory is refined with general matrix formulations and compacted by exploiting general properties of the structure tensor. Theoretical predictions based on the revised theory are presented and compared with experimental results on rendered images. The predicted curves are shown to conform well to expectations when the deviations from normal viewing and surface anisotropy are not large.
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