Investigating user response to a hybrid sketch based interface for creating 3D virtual models in an immersive environment

This research was done in collaboration with the Fraunhofer Institute for Production Systems and Design Technology Berlin. It was supported by VISIONAIR, a project funded by the European Commission under grant agreement 262044.Computer modelling of 2D drawings is becoming increasingly popular in modern design as can be witnessed in the shift of modern computer modelling applications from software requiring specialised training to ones targeted for the general consumer market. Despite this, traditional sketching is still prevalent in design, particularly so in the early design stages. Thus, research trends in computer-aided modelling focus on the the development of sketch based interfaces that are as natural as possible. In this paper, we present a hybrid sketch based interface which allows the user to make draw sketches using offline as well as online sketching modalities, displaying the 3D models in an immersive setup, thus linking the object interaction possible through immersive modelling to the flexibility allowed by paper-based sketching. The interface was evaluated in a user study which shows that such a hybrid system can be considered as having pragmatic and hedonic value.peer-reviewe

Surface reconstruction of ancient water storage systems an approach for sparse 3D sonar scans and fused stereo images

This work presents a process pipeline that addresses the problem of reconstructing surfaces of underwater structures from stereo images and sonar scans collected with a micro-ROV on the islands of Malta and Gozo. Using a limited sensor load, sonar and small GoPro Hero2 cameras, the micro-ROV is able to explore water systems and gather data. As a preprocess to the reconstruction pipeline, a 3D evidence grid is created by mosaicing horizontal and vertical sonar scans. A volumetric representation is then constructed using a level set method. Fine-scale details from the scene are captured in stereo cameras, and are transformed into point clouds and projected into the volume. A raycasting technique is used to trim the volume in accordance with the projected point clouds, thus reintroducing fine details to the rough sonar-generated model. The resulting volume is surfaced, yielding a final mesh which can be viewed and interacted with for archaeological and educational purposes. Initial results from both steps of the reconstruction pipeline are presented and discussed.peer-reviewe

On Weighted Regions and Social Crowds: Autonomous-agent Navigation in Virtual Worlds

Virtual environments have gained in importance in many aspects of the world we live in today. Immersive virtual worlds are ubiquitous in modern movies, video games, and online communities. They are also important in non-entertainment applications such as training and education software, simulations of mass events, evacuation scenarios, human factor analysis, and urban city planning. Training and education software itself comprises various application areas, ranging from teaching children with the help of virtual characters, to training policemen and firefighters, or training soldiers in virtual environments for military operations. Other applications are online mapping services such as Open Street Map, Google Street View, or Mapillary. A key aspect of creating an immersive virtual world is the development of algorithms that handle the navigation of its virtual inhabitants. This involves the creation of believable paths that are smooth, do not contain unnecessary detours, keep clearance from obstacles, respect terrain and region information, and avoid collisions with other moving entities. Furthermore, it involves the coordination of large virtual crowds in both sparse and dense situations, and the generation of social behavior among virtual groups. State-of-the-art algorithms and crowd-simulation models struggle with such tasks, and consequently, the range of possible character behaviors is still limited up to the present day. This thesis focuses on three computational tasks, with which state-of-the-art algorithms still struggle: Region-based path planning, region-based path following, and coordinating dense virtual crowds and social groups. We show why these tasks are difficult to solve with existing algorithms when using grids or graph-based representations of the traversable space in a virtual environment. Furthermore, we show that these tasks can be solved efficiently on a surface-based representation when using novel methods. These novel methods on region-based planning and coordinating crowds and social groups are presented in detail, and they form the main contributions of this thesis

Navigating Through Virtual Worlds: From Single Characters to Large Crowds

With the rise and success of digital games over the past few decades, path planning algorithms have become an important aspect in modern game development for all types of genres. Indirectly-controlled playable characters as well as non-player characters have to find their way through the game's environment to reach their goal destinations. Modern gaming hardware and new algorithms enable the simulation of large crowds with thousands of individual characters. Still, the task of generating feasible and believable paths in a time- and storage-efficient way is a big challenge in this emerging and exciting research field. In this chapter, the authors describe classical algorithms and data structures, as well as recent approaches that enable the simulation of new and immersive features related to path planning and crowd simulation in modern games. The authors discuss the pros and cons of such algorithms, give an overview of current research questions and show why graph-based methods will soon be replaced by novel approaches that work on a surface-based representation of the environment

Dynamically Pruned A* for Re-planning in Navigation Meshes

Modern simulations feature crowds of AI-controlled agents moving through dynamic environments, with obstacles appearing or disappearing at run-time. A dynamic navigation mesh can represent the traversable space of such environments. The A* algorithm computes optimal paths through the dual graph of this mesh. When an obstacle is inserted or removed, the mesh changes and agents should re-plan their paths. Many existing re-planning algorithms are too memory-intensive for crowds, or they cannot easily be used on graphs that structurally change. In this paper, we present Dynamically Pruned A* (DPA*), an extension of A* for re-planning optimal paths in dynamic navigation meshes. DPA* has similarities to adaptive algorithms that make the A* heuristic more informed based on previous queries. However, DPA* prunes the search using only the previous path and its relation to the dynamic event. We describe this relation using four scenarios; DPA* uses different rules in each scenario. Our algorithm is memory-friendly and robust against structural changes, which makes it suitable for crowds in dynamic navigation meshes. Experiments show that DPA* performs particularly well in large environments and when the dynamic event is visible to the agent. We integrate the algorithm into crowd simulation software to model large crowds in dynamic environments in real-time

Bounding the Locus of the Center of Mass for a Part with Shape Variation

The shape and center of mass of a part are crucial parameters to algorithms for planning automated manufacturing tasks. As industrial parts are generally manufactured to tolerances, the shape is subject to variations, which, in turn, also cause variations in the location of the center of mass. Planning algorithms should take into account both types of variation to prevent failure when the resulting plans are applied to manufactured incarnations of a model part. We study the relation between variation in part shape and variation in the location of the center of mass for a part with uniform mass distribution. We consider a general model for shape variation that only assumes that every valid instance contains a shape PI while it is contained in another shape PE. We characterize the worst-case displacement of the center of mass in a given direction in terms of PI and PE. The characterization allows us to determine an adequate polytopic approximation of the locus of the center of mass. We also show that the worst-case displacement is small if PI is convex and fat and the distance between the boundary of PE and PI is bounded