  Accurate 3D tracking in highly deformable scenes with occlusions and shadows
can facilitate new applications in robotics, augmented reality, and generative
AI. However, tracking under these conditions is extremely challenging due to
the ambiguity that arises with large deformations, shadows, and occlusions. We
introduce MD-Splatting, an approach for simultaneous 3D tracking and novel view
synthesis, using video captures of a dynamic scene from various camera poses.
MD-Splatting builds on recent advances in Gaussian splatting, a method that
learns the properties of a large number of Gaussians for state-of-the-art and
fast novel view synthesis. MD-Splatting learns a deformation function to
project a set of Gaussians with non-metric, thus canonical, properties into
metric space. The deformation function uses a neural-voxel encoding and a
multilayer perceptron (MLP) to infer Gaussian position, rotation, and a shadow
scalar. We enforce physics-inspired regularization terms based on local
rigidity, conservation of momentum, and isometry, which leads to trajectories
with smaller trajectory errors. MD-Splatting achieves high-quality 3D tracking
on highly deformable scenes with shadows and occlusions. Compared to
state-of-the-art, we improve 3D tracking by an average of 23.9 %, while
simultaneously achieving high-quality novel view synthesis. With sufficient
texture such as in scene 6, MD-Splatting achieves a median tracking error of
3.39 mm on a cloth of 1 x 1 meters in size. Project website:
https://md-splatting.github.io/.
