Antonio Susín

Biomechanical Validation of Upper-Body and Lower-Body Joint Movements of Kinect Motion Capture Data for Rehabilitation Treatments

New and powerful hardware like Kinect introduces the possibility of changing biomechanics paradigm, usually based on expensive and complex equipment. Kinect is a markerless and cheap technology recently introduced from videogame industry. In this work we conduct a comparison study of the precision in the computation of joint angles between Kinect and an optical motion capture professional system. We obtain a range of disparity that guaranties enough precision for most of the clinical rehabilitation treatments prescribed nowadays for patients. This way, an easy and cheap validation of these treatments can be obtained automatically, ensuring a better quality control process for the patients rehabilitation.

Non structured meshes for Cloth GPU simulation using FEM

We present a Finite Element Method (FEM) implementation for cloth simulation on the GPU. The advantages of FEM are twofold: the realism of cloth simulations using this method is improved compared with other methods like the widely used mass-spring one, and it has a wider application rank because it can be used for general triangulated cloth meshes. We are able to detect collisions between cloth and other objects (solids or deformables) and also we deal with self cloth collisions. This is also done in the GPU using image-based collision methods. We have also improved a GPU-Gradient Conjugate method for solving the linear equation systems involved in the FEM solution. Two more methods are also implemented in the GPU to compare with the FEM method: a mass-spring model (based on rectangular meshes) and a constraint method (based on triangular meshes).

Transferring the Rig and Animations from a Character to Different Face Models

We introduce a facial deformation system that allows artists to define and customize a facial rig and later apply the same rig to different face models. The method uses a set of landmarks that define specific facial features and deforms the rig anthropometrically. We find the correspondence of the main attributes of a source rig, transfer them to different three‐demensional (3D) face models and automatically generate a sophisticated facial rig. The method is general and can be used with any type of rig configuration. We show how the landmarks, combined with other deformation methods, can adapt different influence objects (NURBS surfaces, polygon surfaces, lattice) and skeletons from a source rig to individual face models, allowing high quality geometric or physically‐based animations. We describe how it is possible to deform the source facial rig, apply the same deformation parameters to different face models and obtain unique expressions. We enable reusing of existing animation scripts and show how shapes nicely mix one with the other in different face models. We describe how our method can easily be integrated in an animation pipeline. We end with the results of tests done with major film and game companies to show the strength of our proposal.

Cage Based Deformations: A Survey

Cage based deformation techniques aims to be an easy to use tool for graphics modeling, texturing and animation. In this paper we describe the most important methods, their foundations, and the desirable properties that they should satisfy. We also present a comparative to show the strong and weak points of each one, taking into account their distinctive utilities. Finally, we discuss some applications that exploit cage capabilities in order to create a more complex deformation system or to simplify other deformation techniques.

Recovering 3D metric structure and motion from multiple uncalibrated cameras

An optimized linear factorization method for recovering both the 3D geometry of a scene and the camera parameters from multiple uncalibrated images is presented. In a first step, we recover a projective approximation using a well-known iterative approach. Then we are able to upgrade from a projective to a Euclidean structure by computing the projective distortion matrix in a way that is analogous to estimating the absolute quadric. Using singular value decomposition (SVD) as the main tool, and from a study of the ranks of the matrices involved in the process, we are able to enforce an accurate Euclidean reconstruction. Moreover, in contrast to other approaches, our process is essentially a linear one and does not require an initial estimation of the solution. Examples of synthetic and real data reconstructions are presented.

Robust Treatment of Degenerate Elements in Interactive Corotational FEM Simulations

We address the problem of robust and efficient treatment of element collapse and inversion in corotational FEM simulations of deformable objects in two and three dimensions, and show that existing degeneration treatment methods have previously unreported flaws that seriously threaten robustness and physical plausibility in interactive applications. We propose a new method that avoids such flaws, yields faster and smoother degeneration recovery and extends the range of well-behaved degenerate configurations without adding significant complexity or computational cost to standard explicit and quasi-implicit solvers.We address the problem of robust and efficient treatment of element collapse and inversion in corotational FEM simulations of deformable objects in two and three dimensions, and show that existing degeneration treatment methods have previously unreported flaws that seriously threaten robustness and physical plausibility in interactive applications. We propose a new method that avoids such flaws, yields faster and smoother degeneration recovery and extends the range of well‐behaved degenerate configurations without adding significant complexity or computational cost to standard explicit and quasi‐implicit solvers.

Simulation and study of the behaviour of the transversalis fascia in protecting against the genesis of inguinal hernias

Simulating the muscular system has many applications in biomechanics, biomedicine and the study of movement in general. We are interested in studying the genesis of a very common pathology: human inguinal hernia. We study the effects that some biomechanical parameters have on the dynamic simulation of the region, and their involvement in the genesis of inguinal hernias. We use the finite element method (FEM) and current models for the muscular contraction to determine the deformed fascia transversalis for the estimation of the maximum strain. We analysed the effect of muscular tissue density, Youngs modulus, Poissons coefficient and calcium concentration in the genesis of human inguinal hernia. The results are the estimated maximum strain in our simulations, has a close correlation with experimental data and the accepted commonly models by the medical community. Our model is the first study of the effect of various biological parameters with repercussions on the genesis of the inguinal hernias.

Camera calibration of long image sequences with the presence of occlusions

Camera calibration is a critical problem in applications such as augmented reality and image based model reconstruction. When constructing a 3D model of an object from an uncalibrated video sequence, large amounts of frames and self occlusions of parts of the object are common and difficult problems. In this paper we present a fast and robust algorithm that uses a divide and conquer strategy to split the video sequence into sub-sequences containing only the most relevant frames. Then a robust stratified linear based algorithm is able to calibrate each of the subsequences to a metric structure and finally the subsequences are merged together and a final nonlinear optimization refines the solution. Examples of real data reconstructions are presented.

Left ventricle volume estimation from 3D SPECT reconstruction

Our approach describes three-dimensional reconstruction of the internal and external surfaces of the human left ventricle from actual SPECT data. The reconstruction is the first process fitting in a complete VR application that will serve as an important diagnosis tool for hospitals. Beginning with surface reconstruction, the application will provide volume and interactive real-time manipulation with the model. We focus on speed, precision and smoothness for the final surfaces. We present recoveries with non-missing data and partial missing data, performed using different fillings for a PHANTOM test volume. We also present a reconstructed cardiac cycle from actual patient data, along with its associated ejection fraction estimation.

Enhanced Lattice Boltzmann Shallow Waters for Real-time Fluid Simulations

We present a novel approach at simulating fluids in real-time by coupling the Lattice Boltzmann Method for Shallow Waters with particle systems. The LBM can handle arbitrary underlying terrain and arbitrary fluid depth, which, in turn, allows us to extend it to track dry regions. The LBM is also two-way coupled with rigid bodies. The particle system adds more detail to the LBM; breaking waves are detected from the surface simulation and particles are generated to provide the effect, taking effectively certain amounts of fluid and reintegrating it back once they fall over again. Both the LBM and the particle simulation are implemented in CUDA, although rigid bodies are simulated in CPU. Finally, we show the effectiveness of the method on commodity hardware.