This paper addresses the challenge of 3D human pose estimation from a single color image. Despite the general success of the end-to-end learning paradigm, top performing approaches employ a two-step solution consisting of a Convolutional Network (ConvNet) for 2D joint localization only and recover 3D pose by a subsequent optimization step. In this paper, we identify the representation of 3D pose as a critical issue with current ConvNet approaches and make two important contributions towards validating the value of end-to-end learning for this task. First, we propose a fine discretization of the 3D space around the subject and train a ConvNet to predict per voxel likelihoods for each joint. This creates a natural representation for 3D pose and greatly improves performance over the direct regression of joint coordinates. Second, to further improve upon initial estimates, we employ a coarse-to-fine prediction scheme. This step addresses the large dimensionality increase and enables iterative refinement and repeated processing of the image features. The proposed approach allows us to train a ConvNet that outperforms all state-of-the-art approaches on standard benchmarks achieving relative error reduction greater than 35% on average. Additionally, we investigate using our volumetric representation in a related architecture which is suboptimal compared to our end-to-end approach, but is of practical interest, since it enables training when no image with corresponding 3D groundtruth is available, and allows us to present compelling results for in-the-wild images.

本研究通过对3D人体姿态估计表征问题的认真研究，提出了一种方法，并且对现有的最优解的表现进行了超越，在标准测试基准中相对误差降低超过30％，该方法包括Convolutional Network、端到端的学习模型、从粗到细的预测方案和三维体表示。

单视图粗细层次三维人体姿态预测