  We present a system to recover the 3D shape and motion of a wide variety of
quadrupeds from video. The system comprises a machine learning front-end which
predicts candidate 2D joint positions, a discrete optimization which finds
kinematically plausible joint correspondences, and an energy minimization stage
which fits a detailed 3D model to the image. In order to overcome the limited
availability of motion capture training data from animals, and the difficulty
of generating realistic synthetic training images, the system is designed to
work on silhouette data. The joint candidate predictor is trained on
synthetically generated silhouette images, and at test time, deep learning
methods or standard video segmentation tools are used to extract silhouettes
from real data. The system is tested on animal videos from several species, and
shows accurate reconstructions of 3D shape and pose.
