Category Archives: Colloquia

CG Colloquium Thursday January 16th

You are cordially invited to attend our CG Colloquium on Thursday, January 16th, 2020, 15:45-17:45h, EWI-Lecture Hall D@ta.

The program features the following two speakers:

Nouri Khalass

Title: Visualizing Axial-Symmetrical Nebula

Abstract: Nebulas are both interesting astrophysical phenomena as well as one of natures most beautiful sights to behold. Their astrophysical relevance comes from the fact that they can be the birthplace of new stars but also the remains of older stars. On top of that, nebulas have appeared countless times when depicting “space” in the entertainment industry. There exists a class of nebula that have a pronounced symmetry in their appearance. The goal is to create a tool that allows the user to model these kinds of nebula. By exploiting this symmetry the user does not have to model the complete nebula, but only a section of the nebula and from this a complete nebula can be synthesized.

Marie Kegeleers

Title: Interactive Story Authoring in Augmented Reality

Abstract: Augmented reality (AR) is a relatively new kind of technology that can be used as a tool to facilitate tasks that benefit from real time interaction and 3D visualisation in a real-world environment. An example of these tasks is story authoring. A story authoring application in AR allows the author to easily visualise story mechanics like plot points, as well as the authored scene with characters and props. Because AR integrates virtual elements with the real world, it offers more direct interaction with story elements which can provide a more intuitive experience compared to a PC application. This project introduces a new interface for AR in a tabletop environment using a head mounted device, that aims to facilitate the story authoring process through its different approach to interaction and visualisation. The interface provides a new way of interaction with virtual elements by combining both physical markers and hand gesture input. The tabletop environment is used to visualise the story authoring elements dynamically, in 3D, to avoid cluttering and enable adaptability. The goal of this combination of interaction and visualisation concepts is to provide a more intuitive story authoring experience.

Computer graphics colloquium Image Synthesis of the Future

You are kindly invited to join the colloquium “Image Synthesis of the Future” on the 18th from 14:00 – 16:00 in the Social Data Lab of the VMB building. During this event, we will experience several renowned speakers:

Ulf Assarsson of Chalmers University
Prof. Assarsson is an expert in real-time shadow computation and large-scale scene representations, including applications to 3D printing.

Jacco Bikker of Utrecht University
Dr. Bikker is the author of the famous Brigade renderer, a path tracer for real-time applications.

Jacob Munkberg of NVIDIA research
Dr. Munkberg worked for Intel and NVIDIA and is responsible for many influential papers on image reconstruction for real-time rendering.

Mark Stamminger
Prof. Stamminger, chair for computer graphics in Erlangen, is known for his many contributions to real-time rendering, including the seminal work on perspective shadow maps, as well as 3D reconstruction and VR/stereo rendering applications.

Each of the speakers will share their insights on the domain and share their views on the field.

CG Colloquium Thursday May 16th

You are cordially invited to attend our CG Colloquium on Thursday, May 16, 2019, 15:45-17:45h, at Pulse-Technology.

The program features the following two speakers:

Gijs Reichert

Title: Improving video analysis for the Olympic dinghy class sailing coaches and athletes

Abstract: Nowadays technology and data analytics are becoming increasingly intertwined with sports. The data can help assess performance during training and in competitive settings. However, for most sailors in the Olympic dinghy class it holds that the use of sensors during training is not standard practice and not allowed during races. To record and review their performance the coaches and athletes make use of video, shot (often by holding a camera in hand) from the a coach boat. The goal is to improve the capture, processing and analysis of videos used to train sailing athletes in the dinghy class. More specifically, the stabilization and quality of the footage taken from the coach boat that follows athletes will be improved. Next to this, of the entire recorded session only the interesting parts for the coach and athletes will be highlighted and extracted. To achieve this segmentation into clips object tracking will be used as well as methods to detect sailing manoeuvres. From these video clips the heel angle, position in boat and rudder movements can be extracted or enhanced to support the coaches in their assessment. The proposed approach should lead to a time-saving method to extract more information from the videos previously possible to support the training of the dutch Olympic sailing team.

Levi van Aanholt

Title: Semantic Tile Solving for Procedural Generation of Architectural Spaces

Abstract: We present an offline tile solving technique to generate complex architectural spaces. The generation is controlled by the notion of an architectural profile. An architectural profile allows to declaritively control spatial creation. It consists of semantic tiles representing building elements and declarative rules to control the generation according to architectural relations. This problem is converted to an ASP logic program and subsequently solved by an ASP solver. Our technique results in a declarative architecture generator that unifies procedurally generating building exterior, building interior and traversal in one system.

CG Colloquium Thursday May 2nd

You are cordially invited to attend our CG Colloquium on Thursday, May 2nd, 2019, 15:45-17:45h, at Pulse Hall 4

The program features the following three speakers:

Huinan Jiang

Title: Player model analysis for adaptive content delivery in an educational game

Abstract: Player in games has been a useful way for understanding player motivation, style and preferences, assisting us to predict their behaviour, adapt the and improve user experience. For serious games, learning is also an factor to consider. Most work done in this area is about adaptive difficulty. While in our educational game Squla, students are exposed to multiple game types, it’s interesting to know how their behavioural data could their game type preference, and whether custom game type delivery could improve students’ engagement and learning. Therefore we present a player analysis method game adaptation, and experiment with target student groups to look into the impact.

Antony Löbker

Title: Automatic reconstruction of real-world buildings using open data

Abstract: Using publicly available data , such as Google streetview panoramas and OpenStreetMap building, it is possible to reconstruct real-world buildings. While these are not highly detailed, they will give a general impression of a. The proposed method can quickly reconstruction an entire neighbourhood in major urban centers around the world.

Julie Hongping Feng

Title: Building a 4D MRI blood flow statistical model

Abstract: Cardiovascular (CVDs) are the global number one cause of death. Current of CVDs is mainly based on functions and morphology of cardiovascular, and 4D MRI blood flow data has become a new and powerful source of, which allows both anatomical and functional analysis in a single. However, it is still difficult to efficiently utilize this data source diagnose CVDs. One of the main reasons is the lack of standard analysis and understanding of this rather new imaging modality. The method to understand the healthy behaviour and its variation is to build an atlas. Current blood flow atlas do not support 3D velocity vector field full information. We attempt to build a 4D MRI blood flow atlas similar to statistical shape and appearance models by applying Principal Component Analysis (PCA) to get the mean and main variations of the blood flow fields. The of this atlas would help physicians understand the 4D MRI data and assist them to identify whether the data is abnormal or not. In order to more efficient representations of variations for vector fields, we also tested Complex PCA and Quaternion PCA, besides traditional Real PCA. Finally, will visualize the results such that they can be interpretable.

CG Colloquium Thursday April 18th

You are cordially invited to attend our CG Colloquium on Thursday, April 18, 2019, 15:45-17:45h, at Pulse Hall 4 .

The program features the following three speakers:

Remi van der Laan

Title: Enhancing Compression of the Sparse Voxel Directed Acyclic Graph

Abstract: Rendering massive scenes in real time represented as voxels has emerged as an attractive alternative compared to the traditional rendering pipeline. This has been achieved through the development of data structures that can efficiently store the scene data while also being inexpensive to traverse. The Sparse Voxel Directed Acyclic Graph is such a data structure, which losslessly compresses geometry by exploiting the spatial coherence in the scene. We attempt enhance the effectiveness of this compression through modifications to the construction of the graph and investigate possibility of applying lossy compression techniques.

Hao Ming Ye

Title: not available at the moment

Abstract: not available at the moment

Ruben Wiersma

Title: Graph Convolutional Networks for Learning on Point Clouds

Abstract: In the past decade, Convolutional Neural Networks (CNNs) have achieved incredible results. A recent development in the deep learning community is the attempt to generalise the advantages of CNNs from a Euclidean domain to non-Euclidean domains, like graphs and manifolds. Some examples of graph data are social networks, regulatory networks, functional networks, and 3D shapes. We attempt to get an understanding of the methods currently available and aim to improve on the current methodology for learning on point clouds. A tentative conclusion is that the conceptually simple Graph Convolutional Network by Kipf and Welling could be improved for manifolds through the incorporation of the connection Laplacian from vector diffusion maps.

CG Colloquium Thursday April 4th

You are cordially invited to attend our Computer Graphics and Visualization Seminar on Thursday, April 4, 2019, 15:45-17:45h, at Pulse Hall 7.

The program features the following three speakers:

Ruben VroegindeWeij (PRELIMINARY)
Title: Motion in Image
Abstract: We present a method to encode motion in a single image by mixing frames from different time origins with a simple user interface.

Mark van de Ruit
Title: Pre-Estimated Spectral Rendering
Abstract: Spectral Monte-Carlo rendering algorithms are suited for reproducing several advanced light phenomena such as dispersion and colored particle scattering. However, spectral rendering comes at the cost of increased (colored) image noise, as now additional samples are required in the spectral domain. We propose to iteratively build estimates of the spectral distributions in a scene during rendering, and use these estimates to guide sampling of the spectral domain. This method can lower variance from spectral sampling in specific situations, which is demonstrated with a working implementation in a conventional path tracer.

Felix Yang
Title: Adaptive Multi-view Ambient Occlusion
Abstract: Screen-space ambient occlusion and obscurance is a group of techniques that approximate the ambient occlusion or obscurance lighting model in the screen-space. They are ubiquitously adopted in modern video games, but suffer from view-dependent artifacts. One possible method to remedy such artifacts is using additional auxiliary cameras to aid the computation, but the improvement diminishes if the auxiliary cameras have poor coverage of the main scene. This project aims to develop techniques to adaptively manipulate the auxiliary cameras to ensure good coverages, therefore a more stable improvement over the single-view result.

Workshop Visual Analytics and Applications

You are all cordially invited to workshop visual analytics and applications, which will take place on 8th of April, from 14:00-17:00 at Pulse-hall 4. Please find detailed program below.

14:00 Jean Daniel Fekete: “Exploring the Evolution of Relationships with Dynamic Hypergraphs”

14:40 Renata Raidou: “Employing Visual Analytics for the Exploration and Prediction”

15:20 Break

15:30 Cagatay Turkay: “Informed computational modelling through visual analytics”

Abstract: With the increasing availability of computational data analysis and modelling tools that can be utilised out-of-the-box, the route from data to results is now much shorter. However, these advancements also come together their own limitations, and a data scientists need to be aware of the pitfalls and act carefully to question every observation and method used within each step of the data analysis process. Visual analytics approaches where interactive visualisations are coupled tightly with the algorithms offer effective methodologies in conducting data science in such inquisitive, rigorous ways. This talk will discuss how visual analytics can facilitate such practices and will look at examples of research on how data can be transformed and visualised creatively in multiple perspectives, on how comparisons can be made within different models, parameters, and within local and global solutions, and on how interaction is an enabler for such processes.

16:10 Thomas Hollt: Cytosplore: Visual Analytics for Single-Cell Profiling of the Immune System
Recent advances in single-cell acquisition technology have led to a shift towards single-cell analysis in many fields of biology. In immunology, detailed knowledge of the cellular composition is of interest, as it can be the cause of deregulated immune responses, which cause diseases. Similarly, vaccination is based on triggering proper immune responses; however, many vaccines are ineffective or only work properly in a subset of those who are vaccinated. Identifying differences in the cellular composition of the immune system in such cases can lead to more precise treatment. Cytosplore is an integrated, interactive visual analysis framework for the exploration of large single-cell datasets. We have developed Cytosplore in close collaboration with immunology researchers and several partners use the software in their daily workflow. Cytosplore enables efficient data analysis and has led to several discoveries alongside high-impact publications.

16:50 end

CG Colloquium Thursday March 21st

You are cordially invited to attend our Computer Graphics and Visualization Seminar on Thursday, March 21, 2019, 15:45-17:45h, at EWI-Lecture hall Chip.

The program features the following three speakers:

David Alderliesten
Title: Continuum Crowds
Abstract: We present a real-time crowd model based on continuum dynamics. In our model, a dynamic potential field simultaneously integrates global navigation with moving obstacles such as other people, efficiently solving for the motion of large crowds without the need for explicit collision avoidance. Simulations created with our system run at interactive rates, demonstrate smooth flow under a variety of conditions, and naturally exhibit emergent phenomena that have been observed in real crowds.

Remco de Vos
Title: Tile-based Pattern Design with Topology Control
Abstract: Patterns with desired aesthetic appearances and physical structures are ubiquitous. However, such patterns are challenging to produce−manual authoring requires significant expertise and efforts while automatic computation lacks sufficient flexibility and user control. We propose a method that automatically synthesizes vector patterns with visual appearance and topological structures designated by users via input exemplars and output conditions. The input can be an existing vector graphics design or a new one manually drawn by the user through our interactive interface. Our system decomposes the input pattern into constituent components (tiles) and overall arrangement (tiling). The tile sets are general and flexible enough to represent a variety of patterns, and can produce different outputs with user specified conditions such as size, shape, and topological properties for physical manufacturing.

Vera Hoveling
Final Bachelor presentation by Vera Hoveling.

CG Colloquium Thursday March 7th

Computer Graphics and Visualization Seminar on Thursday, March 7, 2019, 15:45-17:45h, at EWI-Lecture hall Chip.

The program features the following two speakers:

Remi van der Laan

Title: Exploiting Coherence in Time-Varying Voxel Data

Abstract: We encode time-varying voxel data for efficient storage and streaming. We store the equivalent of a separate sparse voxel octree for each frame, but utilize both spatial and temporal coherence to reduce the amount of memory needed. We represent the time-varying voxel data in a single directed acyclic graph with one root per time step. In this graph, we avoid storing identical regions by keeping one unique instance and pointing to that from several parents. We further reduce the memory consumption of the graph by minimizing the number of bits per pointer and encoding the result into a dense bitstream.

Michiel van Spaendonck

Title: Spatiotemporal Variance-Guided Filtering: Real-Time Reconstruction for Path-Traced Global Illumination

Abstract: We introduce a reconstruction algorithm that generates a temporally stable sequence of images from one path-per-pixel global illumination. To handle such noisy input, we use temporal accumulation to increase the effective sample count and spatiotemporal luminance variance estimates to drive a hierarchical, image-space wavelet filter. This hierarchy allows us to distinguish between noise and detail at multiple scales using local luminance variance.

Physically based light transport is a long-standing goal for real-time computer graphics. While modern games use limited forms of ray tracing, physically based Monte Carlo global illumination does not meet their 30Hz minimal performance requirement. Looking ahead to fully dynamic real-time path tracing, we expect this to only be feasible using a small number of paths per pixel. As such, image reconstruction using low sample counts is key to bringing path tracing to real-time. When compared to prior interactive reconstruction filters, our work gives approximately 10x more temporally stable results, matches reference images 5-47% better (according to SSIM), and runs in just 10ms (+- 15%) on modern graphics hardware at 1920×1080 resolution.

CG Colloquium Thursday February 21st

You are cordially invited to attend our Computer Graphics and Visualization Seminar on Thursday, February 21, 2019, 15:45-17:45h, at EWI-Lecture hall Chip.

The program features the following two speakers:

Nouri Khalass
Title: Visualizing Stars and Emission Nebulae
Abstract: We describe the star and nebula visualization techniques used to create a 3D volumetric visualization of the Orion Nebula. The nebula’s ionization layer is modeled first as a surface model, derived from infrared and visible light observations. The model is imported into a volume scene graph-based volume visualization system to simulate the nebula’s emissive gases. Stars are rendered using Gaussian spots that are attenuated with distance.

Mark van de Ruit
Title: Real-Time Polygonal-Light Shading with Linearly Transformed Cosines
Abstract: In this paper, we show that applying a linear transformation—represented by a 3 x 3 matrix—to the direction vectors of a spherical distribution yields another spherical distribution, for which we derive a closed-form expression. With this idea, we can use any spherical distribution as a base shape to create a new family of spherical distributions with parametric roughness, elliptic anisotropy and skewness. If the original distribution has an analytic expression, normalization, integration over spherical polygons, and importance sampling, then these properties are inherited by the linearly transformed distributions.

By choosing a clamped cosine for the original distribution we obtain a family of distributions, which we call Linearly Transformed Cosines (LTCs), that provide a good approximation to physically based BRDFs and that can be analytically integrated over arbitrary spherical polygons. We show how to use these properties in a realtime polygonal-light shading application. Our technique is robust, fast, accurate and simple to implement.