Browsing by Author "Ma, Lizhuang"

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    Intrinsic Image Decomposition Using Multi‐Scale Measurements and Sparsity
    (© 2017 The Eurographics Association and John Wiley & Sons Ltd., 2017) Ding, Shouhong; Sheng, Bin; Hou, Xiaonan; Xie, Zhifeng; Ma, Lizhuang; Chen, Min and Zhang, Hao (Richard)
    Automatic decomposition of intrinsic images, especially for complex real‐world images, is a challenging under‐constrained problem. Thus, we propose a new algorithm that generates and combines multi‐scale properties of chromaticity differences and intensity contrast. The key observation is that the estimation of image reflectance, which is neither a pixel‐based nor a region‐based property, can be improved by using multi‐scale measurements of image content. The new algorithm iteratively coarsens a graph reflecting the reflectance similarity between neighbouring pixels. Then multi‐scale reflectance properties are aggregated so that the graph reflects the reflectance property at different scales. This is followed by a sparse regularization on the whole reflectance image, which enforces the variation in reflectance images to be high‐frequency and sparse. We formulate this problem through energy minimization which can be solved efficiently within a few iterations. The effectiveness of the new algorithm is tested with the Massachusetts Institute of Technology (MIT) dataset, the Intrinsic Images in the Wild (IIW) dataset, and various natural images.Automatic decomposition of intrinsic images, especially for complex real‐world images, is a challenging under‐constrained problem. Thus, we propose a new algorithm that generates and combines multi‐scale properties of chromaticity differences and intensity contrast. The key observation is that the estimation of image reflectance, which is neither a pixel‐based nor a region‐based property, can be improved by using multi‐scale measurements of image content. The new algorithm iteratively coarsens a graph reflecting the reflectance similarity between neighbouring pixels.
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    Monocular Human Pose and Shape Reconstruction using Part Differentiable Rendering
    (The Eurographics Association and John Wiley & Sons Ltd., 2020) Wang, Min; Qiu, Feng; Liu, Wentao; Qian, Chen; Zhou, Xiaowei; Ma, Lizhuang; Eisemann, Elmar and Jacobson, Alec and Zhang, Fang-Lue
    Superior human pose and shape reconstruction from monocular images depends on removing the ambiguities caused by occlusions and shape variance. Recent works succeed in regression-based methods which estimate parametric models directly through a deep neural network supervised by 3D ground truth. However, 3D ground truth is neither in abundance nor can efficiently be obtained. In this paper, we introduce body part segmentation as critical supervision. Part segmentation not only indicates the shape of each body part but helps to infer the occlusions among parts as well. To improve the reconstruction with part segmentation, we propose a part-level differentiable renderer that enables part-based models to be supervised by part segmentation in neural networks or optimization loops. We also introduce a general parametric model engaged in the rendering pipeline as an intermediate representation between skeletons and detailed shapes, which consists of primitive geometries for better interpretability. The proposed approach combines parameter regression, body model optimization, and detailed model registration altogether. Experimental results demonstrate that the proposed method achieves balanced evaluation on pose and shape, and outperforms the state-of-the-art approaches on Human3.6M, UP-3D and LSP datasets.