15 December 2017 (Time: 15:15-17:00 Location: BBG-214)

Title: Navigation for Characters and Crowds in Complex Virtual Environments
Speaker: Wouter van Toll (PhD)
 Bio: Dr. Wouter van Toll is a lecturer at Utrecht University. He currently teaches the GMT course "Crowd simulation", and he has been a lecturer in the courses "Geometric algorithms" and "Game programming". For his PhD and MSc theses, Wouter developed and implemented algorithms for efficient path planning and crowd simulation in multi-layered 3D environments. Furthermore, Wouter has been in charge of the group's crowd simulation software, which is used both in research and in the simulation industry.
Summary: In a crowd simulation, virtual walking characters need to compute and traverse paths through a virtual environment while avoiding collisions. Real-time crowd simulation requires efficient data structures and algorithms. These were the topics of Wouter van Toll’s PhD thesis. In this presentation, Wouter will give a broad overview of his thesis, and he will zoom in on two chapters: "A comparative study of navigation meshes" and "A generic crowd simulation framework". He will also give a glimpse of what it was like to be a PhD student.

Globally and Locally Consistent Image Completion
Authors: Satoshi Iizuka, Edgar Simo-Serra, Hisroshi Ishikawa
Speakers: Nikita Iefymov and Karim Machlab

 Summary: We present a novel approach for image completion that results in images that are both locally and globally consistent. With a fully-convolutional neural network, we can complete images of arbitrary resolutions by llingin missing regions of any shape. To train this image completion network to be consistent, we use global and local context discriminators that are trained to distinguish real images from completed ones. The global discriminator looks at the entire image to assess if it is coherent as a whole, while the local discriminator looks only at a small area centered at the completed region to ensure the local consistency of the generated patches. The image completion network is then trained to fool the both context discriminator networks, which requires it to generate images that are indistinguishable from real ones with regard to overall consistency as well as in details. We show that our approach can be used to complete a wide variety of scenes. Furthermore, in contrast with the patch-based approaches such as PatchMatch, our approach can generate fragments that do not appear elsewhere in the image, which allows us to naturally complete the images of objects with familiar and highly specific structures, such as faces.

24 November 2017 (Time: 15:15-17:00 Location: BBG-214)

Title: Embodiment in Multimodal Augmented Reality
Speaker: Nina Rosa (PhD candidate)
 Bio: Nina Rosa is a PhD candidate in the Game Research Graduate Program at Utrecht University. She previously obtained her bachelor's degrees in Computer Science and Mathematics, and her master's degree in Game and Media Technology. Her master thesis won the Ngi-NGN Informatie Scriptieprijs 2015, awarded by the KHMW in Haarlem. Nina is currently also a member of the Faculty Council for the Faculty of Science, and a member of the ICS PhD Council.
Summary: Until recently, both virtual reality (VR) and augmented reality (AR) research were primarily focused on improving the visual fidelity of the technological systems. Currently there is a noticeable shift towards more experience-based research where we not only focus on the visual sense but also other senses. Using multiple senses in virtual and augmented environments creates new interesting research opportunities, one of which is the aspect of embodiment. In this presentation I will describe a few challenges and opportunities that multimodality brings in the areas of VR and AR, and show what roles the body can serve in these matters, and how we can manipulate the conventional schema of a body using VR and AR technology.

A Dose of Reality: Overcoming Usability Challenges in VR Head-Mounted Displays
Authors: Mark McGill, Daniel Boland and Roderick Murray-Smith
Speakers: Chrit Hameleers and Sam de Redelijkheid

 Summary: We identify usability challenges facing consumers adopting Virtual Reality (VR) head-mounted displays (HMDs) in a survey of 108 VR HMD users. Users reported significant issues in interacting with, and being aware of their real-world context when using a HMD. Building upon existing work on blending real and virtual environments, we performed three design studies to address these usability concerns. In a typing study, we show that augmenting VR with a view of reality significantly corrected the performance impairment of typing in VR. We then investigated how much reality should be incorporated and when, so as to preserve users' sense of presence in VR. For interaction with objects and peripherals, we found that selectively presenting reality as users engaged with it was optimal in terms of performance and users' sense of presence. Finally, we investigated how this selective, engagement-dependent approach could be applied in social environments, to support the user's awareness of the proximity and presence of others.


3 November 2017 (Time: 15:15-17:00 Location: Bestuurs-Lieregg)

Title: Balanced by Design: Predicates in Game Mechanics
Speaker: Ronnie Vanderfeesten (PhD candidate)
 Bio: Ron Vanderfeesten currently is a PHD Student at the University of Utrecht with a Master's Degree in Computer Science and Engineering and a Bachelor's Degree in Applied Physics. He also works part-time at an indie gamedevelopment studio based in The Hague. He has over 15 years of experience in 3d modeling, gamedesign and programming, with an emphasis on the creation of virtual characters.
Summary: If you play a lot of games you might hear things like: "that's so OP" and "They should really nerf class/item/character X, so imba". Addressing those issues and maintaining a good game balance keeps a game healthy and fun for all players. However, the current approach to making game mechanics: "let's design something cool, and we'll balance it later in a patch" leads to requiring frequent (minor) updates and sometimes even situations where the game mechanics are very difficult to balance due to the inherent design of that part of the game. This presentation will show, using simple examples, how one can model the intuitive notion of balance in game mechanics and then use predicates to ensure a set of game mechanics fullfill certain desirable properties by design. We will show how randomness can be used to improve game balance and show a way to systematically detect and exclude loopholes in a game system.

Interactive Reconstruction of Monte Carlo Image Sequences using a Recurrent Denoising Autoencoder
Authors: Chakravarty R. Alla Chaitanya, Anton Kaplanyan, Christoph Schied, Marco Salvi, Aaron, Lefohn, Derek Nowrouzezahrai and Timo Aila
Speakers: Matthijs Lardinoije and Martijn Visser

 Summary: We describe a machine learning technique for reconstructing image sequences rendered using Monte Carlo methods. Our primary focus is on reconstruction of global illumination with extremely low sampling budgets at interactive rates. Motivated by recent advances in image restoration with deep convolutional networks, we propose a variant of these networks better suited to the class of noise present in Monte Carlo rendering. We allow for much larger pixel neighborhoods to be taken into account, while also improving execution speed by an order of magnitude. Our primary contribution is the addition of recurrent connections to the network in order to drastically improve temporal stability for sequences of sparsely sampled input images. Our method also has the desirable property of automatically modeling relationships based on auxiliary per-pixel input channels, such as depth and normals. We show signicantly higher quality results compared to existing methods that run at comparable speeds, and furthermore argue a clear path for making our method run at realtime rates in the near future.


13 October 2017 (Time: 15:15-17:00 Location: Bestuurs-Lieregg)

Title: Introduction to GMT Colloquium (pdf)
Speaker: Dr. Zerrin Yumak
Bounce Maps: An Improved Restitution Model for Real-time Rigid-Body Impact
Authors: Jui-Hsien Wang, Rajsekhar Setaluri, Doug L. James, and Dinesh K. Pai
Speakers: Jeroen Huisen and Navid Saremi
 Summary: We present a novel method to enrich standard rigid-body impact models with a spatially varying coefficient of restitution map, or Bounce Map. Even state-of-the art methods in computer graphics assume that for a single rigid body, post- and pre-impact dynamics are related with a single global, constant, namely the coefficient of restitution. We first demonstrate that this assumption is highly inaccurate, even for simple objects. We then present a technique to efficiently and automatically generate a function which maps locations on the object’s surface along with impact normals, to a scalar coefficient of restitution value. Furthermore, we propose a method for two-body restitution analysis, and, based on numerical experiments, estimate a practical model for combining one-body Bounce Map values to approximate the two-body coefficient of restitution. We show that our method not only improves accuracy, but also enables visually richer rigid-body simulations.

A Review of Building Evacuation Models
Authors: Erica D. Kuligowski, Richard D. Peacock and Bryan L. Hoskins
Speaker: Yiran Zhao

 Summary: Evacuation calculations are increasingly becoming a part of performance-based analyses to assess the level of life safety provided in buildings. In some cases, engineers are using back-of-the-envelope (hand) calculations to assess life safety, and in others, computational evacuation models are being used. This paper presents a review of 26 current computer evacuation models, and is an updated version of a previous review published in 2005. Models are categorized by their availability, overarching method of simulating occupants, purpose, type of grid/structure, perspective of the occupants, perspective of the building, internal algorithms for simulating occupant behavior and movement, the incorporate of fire effects, the use of computer-aided design drawings, visualization methods, and validation techniques. Models are also categorized based upon whether they simulate special features of an evacuation, including counterflow, exit blockages, fire conditions that affect behavior, incapacitation of the occupants due to toxic smoke products, group behavior, disabled or slower-moving occupant effects, pre-evacuation delays, elevator usage, and occupant route choice.