SIGGRAPH

We present a method for recovering a temporally coherent, deforming triangle mesh with arbitrarily changing topology from an incoherent sequence of static closed surfaces. We solve this problem using the surface geometry alone, without any prior information like surface templates or velocity fields. Our system combines a proven strategy for triangle mesh improvement, a robust multi-resolution non-rigid registration routine, and a reliable technique for changing surface mesh topology. We also introduce a novel topological constraint enforcement algorithm to ensure that the output and input always have similar topology. We apply our technique to a series of diverse input data from video reconstructions, physics simulations, and artistic morphs. The structured output of our algorithm allows us to efficiently track information like colors and displacement maps, recover velocity information, and solve PDEs on the mesh as a post process

A HoloLens Framework for Augmented Reality Applications in Breast Cancer Surgery

This project aims to support oncologic breast-conserving surgery by creating a platform for better surgical planning through the development of a framework that is capable of displaying a virtual model of the tumour(s) requiring surgery, on a patient's breast. Breast-conserving surgery is the first clear option when it comes to tackling cases of breast cancer, but the surgery comes with risks. The surgeon wants to maintain clean margins while performing the procedure such that the disease does not resurface. This calls for the importance of surgical planning where the surgeon consults with radiologists and pre-surgical imaging such as Magnetic Resonance Imaging (MRI). The MRI prior to the surgical procedure, however, is taken with the patient in the prone position (face-down) but the surgery happens in a supine position (face-up). Thus mapping the location of the tumour(s) to the corresponding anatomical position from the MRI is a tedious task which requires a large amount of expertise and time given that the organ is soft and flexible. For this project, the tumour is visualized in the corresponding anatomical position to assist in surgical planning. Augmented Reality is the best option for this problem and this, in turn, led to an investigation of the application capability of the Microsoft HoloLens to solve this problem. Given its multitude of sensors and resolution of display the device is a fine candidate for this process. However, the HoloLens is still under development with a large number of limitations in its use. This work tries to compensate for these limitations using the existing hardware and software in the device's arsenal. Within this masters thesis, the principal questions answered are related to the acquiring of data from breast mimicking objects in acceptable resolutions, discriminating between the information based on photometry, offloading the data to a computer for post-processing in creating a correspondence between the MRI data and acquired data, and finally retrieving the processed information such that the MRI information can be used for visualizing the tumor in the anatomically precise position. Unfortunately, time limitations for this project led to an incomplete system which is not completely synchronized, however, our work has solidified the grounds for the software aspects toward the final goals set out such that extensive exploration need only be done in the imaging side of this problem

IST Austria Thesis

Computer graphics is an extremely exciting field for two reasons. On the one hand, there is a healthy injection of pragmatism coming from the visual effects industry that want robust algorithms that work so they can produce results at an increasingly frantic pace. On the other hand, they must always try to push the envelope and achieve the impossible to wow their audiences in the next blockbuster, which means that the industry has not succumb to conservatism, and there is plenty of room to try out new and crazy ideas if there is a chance that it will pan into something useful. Water simulation has been in visual effects for decades, however it still remains extremely challenging because of its high computational cost and difficult artdirectability. The work in this thesis tries to address some of these difficulties. Specifically, we make the following three novel contributions to the state-of-the-art in water simulation for visual effects. First, we develop the first algorithm that can convert any sequence of closed surfaces in time into a moving triangle mesh. State-of-the-art methods at the time could only handle surfaces with fixed connectivity, but we are the first to be able to handle surfaces that merge and split apart. This is important for water simulation practitioners, because it allows them to convert splashy water surfaces extracted from particles or simulated using grid-based level sets into triangle meshes that can be either textured and enhanced with extra surface dynamics as a post-process. We also apply our algorithm to other phenomena that merge and split apart, such as morphs and noisy reconstructions of human performances. Second, we formulate a surface-based energy that measures the deviation of a water surface froma physically valid state. Such discrepancies arise when there is a mismatch in the degrees of freedom between the water surface and the underlying physics solver. This commonly happens when practitioners use a moving triangle mesh with a grid-based physics solver, or when high-resolution grid-based surfaces are combined with low-resolution physics. Following the direction of steepest descent on our surface-based energy, we can either smooth these artifacts or turn them into high-resolution waves by interpreting the energy as a physical potential. Third, we extend state-of-the-art techniques in non-reflecting boundaries to handle spatially and time-varying background flows. This allows a novel new workflow where practitioners can re-simulate part of an existing simulation, such as removing a solid obstacle, adding a new splash or locally changing the resolution. Such changes can easily lead to new waves in the re-simulated region that would reflect off of the new simulation boundary, effectively ruining the illusion of a seamless simulation boundary between the existing and new simulations. Our non-reflecting boundaries makes sure that such waves are absorbed