3,373 research outputs found
MonoPerfCap: Human Performance Capture from Monocular Video
We present the first marker-less approach for temporally coherent 3D
performance capture of a human with general clothing from monocular video. Our
approach reconstructs articulated human skeleton motion as well as medium-scale
non-rigid surface deformations in general scenes. Human performance capture is
a challenging problem due to the large range of articulation, potentially fast
motion, and considerable non-rigid deformations, even from multi-view data.
Reconstruction from monocular video alone is drastically more challenging,
since strong occlusions and the inherent depth ambiguity lead to a highly
ill-posed reconstruction problem. We tackle these challenges by a novel
approach that employs sparse 2D and 3D human pose detections from a
convolutional neural network using a batch-based pose estimation strategy.
Joint recovery of per-batch motion allows to resolve the ambiguities of the
monocular reconstruction problem based on a low dimensional trajectory
subspace. In addition, we propose refinement of the surface geometry based on
fully automatically extracted silhouettes to enable medium-scale non-rigid
alignment. We demonstrate state-of-the-art performance capture results that
enable exciting applications such as video editing and free viewpoint video,
previously infeasible from monocular video. Our qualitative and quantitative
evaluation demonstrates that our approach significantly outperforms previous
monocular methods in terms of accuracy, robustness and scene complexity that
can be handled.Comment: Accepted to ACM TOG 2018, to be presented on SIGGRAPH 201
Robust Temporally Coherent Laplacian Protrusion Segmentation of 3D Articulated Bodies
In motion analysis and understanding it is important to be able to fit a
suitable model or structure to the temporal series of observed data, in order
to describe motion patterns in a compact way, and to discriminate between them.
In an unsupervised context, i.e., no prior model of the moving object(s) is
available, such a structure has to be learned from the data in a bottom-up
fashion. In recent times, volumetric approaches in which the motion is captured
from a number of cameras and a voxel-set representation of the body is built
from the camera views, have gained ground due to attractive features such as
inherent view-invariance and robustness to occlusions. Automatic, unsupervised
segmentation of moving bodies along entire sequences, in a temporally-coherent
and robust way, has the potential to provide a means of constructing a
bottom-up model of the moving body, and track motion cues that may be later
exploited for motion classification. Spectral methods such as locally linear
embedding (LLE) can be useful in this context, as they preserve "protrusions",
i.e., high-curvature regions of the 3D volume, of articulated shapes, while
improving their separation in a lower dimensional space, making them in this
way easier to cluster. In this paper we therefore propose a spectral approach
to unsupervised and temporally-coherent body-protrusion segmentation along time
sequences. Volumetric shapes are clustered in an embedding space, clusters are
propagated in time to ensure coherence, and merged or split to accommodate
changes in the body's topology. Experiments on both synthetic and real
sequences of dense voxel-set data are shown. This supports the ability of the
proposed method to cluster body-parts consistently over time in a totally
unsupervised fashion, its robustness to sampling density and shape quality, and
its potential for bottom-up model constructionComment: 31 pages, 26 figure
Event-based Motion Segmentation with Spatio-Temporal Graph Cuts
Identifying independently moving objects is an essential task for dynamic
scene understanding. However, traditional cameras used in dynamic scenes may
suffer from motion blur or exposure artifacts due to their sampling principle.
By contrast, event-based cameras are novel bio-inspired sensors that offer
advantages to overcome such limitations. They report pixelwise intensity
changes asynchronously, which enables them to acquire visual information at
exactly the same rate as the scene dynamics. We develop a method to identify
independently moving objects acquired with an event-based camera, i.e., to
solve the event-based motion segmentation problem. We cast the problem as an
energy minimization one involving the fitting of multiple motion models. We
jointly solve two subproblems, namely event cluster assignment (labeling) and
motion model fitting, in an iterative manner by exploiting the structure of the
input event data in the form of a spatio-temporal graph. Experiments on
available datasets demonstrate the versatility of the method in scenes with
different motion patterns and number of moving objects. The evaluation shows
state-of-the-art results without having to predetermine the number of expected
moving objects. We release the software and dataset under an open source
licence to foster research in the emerging topic of event-based motion
segmentation
U4D: Unsupervised 4D Dynamic Scene Understanding
We introduce the first approach to solve the challenging problem of
unsupervised 4D visual scene understanding for complex dynamic scenes with
multiple interacting people from multi-view video. Our approach simultaneously
estimates a detailed model that includes a per-pixel semantically and
temporally coherent reconstruction, together with instance-level segmentation
exploiting photo-consistency, semantic and motion information. We further
leverage recent advances in 3D pose estimation to constrain the joint semantic
instance segmentation and 4D temporally coherent reconstruction. This enables
per person semantic instance segmentation of multiple interacting people in
complex dynamic scenes. Extensive evaluation of the joint visual scene
understanding framework against state-of-the-art methods on challenging indoor
and outdoor sequences demonstrates a significant (approx 40%) improvement in
semantic segmentation, reconstruction and scene flow accuracy.Comment: To appear in IEEE International Conference in Computer Vision ICCV
201
Cascaded Scene Flow Prediction using Semantic Segmentation
Given two consecutive frames from a pair of stereo cameras, 3D scene flow
methods simultaneously estimate the 3D geometry and motion of the observed
scene. Many existing approaches use superpixels for regularization, but may
predict inconsistent shapes and motions inside rigidly moving objects. We
instead assume that scenes consist of foreground objects rigidly moving in
front of a static background, and use semantic cues to produce pixel-accurate
scene flow estimates. Our cascaded classification framework accurately models
3D scenes by iteratively refining semantic segmentation masks, stereo
correspondences, 3D rigid motion estimates, and optical flow fields. We
evaluate our method on the challenging KITTI autonomous driving benchmark, and
show that accounting for the motion of segmented vehicles leads to
state-of-the-art performance.Comment: International Conference on 3D Vision (3DV), 2017 (oral presentation
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