Quantifying human reconstruction accuracy for voxelcarving in a sporting environment

Abstract

Whilst voxel carving approaches exist that allow non-invasive 3D human reconstruction, their performance is heavily dependent on the number of cameras used and the placement of these cameras around the subject. We present a technique to quantify the fall-off in accuracy of spatially carved volumetric representations of humans based on real world constraints. We describe an example of such a quantitative evaluation using a synthetic dataset of typical sports motion in a tennis court scenario, created using computer graphics techniques and motion capture data. Experiments are performed using a baseline voxel carving technique that includes player tracking, background subtraction and player voxel carving. This type of quantitative evaluation could be used by amateur sporting clubs without a sophisticated capture infrastructure to understand how best to instrument a camera network in order to obtain a good trade-off between reconstruction accuracy and installation cost.

Persistent Homology for 3D Reconstruction Evaluation

“…Space or voxel carving is a non-invasive technique that is used to produce a 3D volume and can be used in particular for the reconstruction of a 3D human model from images captured from a set of cameras placed around the subject. In [1], the authors present a technique to quantitatively evaluate spatially carved volumetric representations of humans using a synthetic dataset of typical sports motion in a tennis court scenario, with regard to the number of cameras used. In this paper, we compute persistent homology over the sequence of chain complexes obtained from the 3D outcomes with increasing number of cameras.…”

Topological evaluation of volume reconstructions by voxel carving

“…The new insight developed in this paper to evaluate a voxel carving technique significantly enriches the evaluation made in [12] by means of NMSE quantification. Although this is not the standard use of persistent homology, the experimentation carried out has provided valuable information from a topological point of view of the reconstructions process.…”

“…The technique involves capturing a series of synchronised images of an object, and, by analysis of these images and with prior knowledge of the exact threedimensional location of the cameras, deriving an approximation of the shape of the object. The general voxel technique proposed in [10] has been modified and adapted to a specific task, as fully detailed in [12,13]. And it is in fact this specific voxel carving technique that we are evaluating.…”

“…if the distance between voxels decreases then the spatial resolution increases. From experimental observation, authors in [12] found that a three dimensional spatial frequency of 4 cm, i.e. 15,625 samples per cubic metre, was sufficiently adequate for their purposes.…”

“…However, one of the fundamental difficulties with voxel carving is the unavailability of a ground truth from which to derive the accuracy of the technique. In an attempt to provide some quantitatively evaluation of voxel carving Monaghan et al [13] present an evaluation of the technique indirectly via silhouette comparison and in [12] present a method to quantitatively evaluate spatially carved volumetric representations of humans using a synthetic dataset of virtual humans in a tennis court scenario. Such quantification is based on a calculated ground truth and on the computation of Normalised Mean Square Error (NMSE).…”