Virtual Reality and Physically-Based Simulation WS 20/21

Virtual Reality (VR) is a research area at the intersection of computer graphics, physically-based simulation, and 3D human-computer interaction (HCI). novel interaction technologies and interaction metaphors VR and 3D realtime computer games share a lot of algorithmic challenges: in virtual environments (in particular, intuitive and direct metaphors), immersion and presence, and real-time rendering. Another important topic is physically-based simulation in real-time, which tries to simulate real-world phenomena such as fire, cloth, the behavior of rigid objects when colliding with each other, fluids, or objects made of deformable material.

Over the past two decades, VR has established itself as an important tool in several industries, such as manufacturing (e.g., automotive, airspace, ship building), architecture, and pharmaceutical industries. During the past few years, we have been witnessing the second "wave" of VR, this time in the consumer, in particular, in the entertainment markets.

In this course, we will first look at the fundamental methods, and then go on to more advanced algorithms that are needed to build complex and full-fledged VR systems or real-time computer games. Example topics are 3D interaction, physically-based behavior of objects, acoustic rendering, haptics, and collision detection.

The assignments will be mostly practical ones, based on the cross-platform game engine Unreal. Participants will start developing with "visual programming", and later use C++ to solve the assignments.
You are encouraged to work on assignments in small teams.

Some of the topics to be covered (tentatively):

  1. Introduction, basic notions of VR, several example applications
  2. VR technologies: displays, tracking, input devices, scene graphs, game engines
  3. The human visual system and Stereo rendering
  4. Techniques for real-time rendering
  5. Fundamental immersive interaction techniques: fundamentals and principles, 3D navigation, user models, 3D selection, redirected walking, system control
  6. Complex immersive interaction techniques: world-in-miniature, action-at-a-distance, magic lens, etc.
  7. Particle systems
  8. Spring-mass systems
  9. Haptics and force feedback
  10. Collision detection
  11. Acoustic rendering

Note: this list is just tentative and subject to change during the semester.

For Students from Other Institutions

If you are from an educational institution other than University of Bremen, you can still join my course, if you fill out this form and apply as a guest student. When successfull, you will get an account with the Universtity of Bremen, which will allow you to access StudIP. There, you can sign up for the course.


Hybrid teaching mode this year! Students can choose to attend physically in the class room, or join via Zoom or Twitch.
Zoom: the link will be announced in an email via Studip.
Twitch: join the channel .

Exams will be on: March 29 through 31. Please register via Studip.


The following table will, eventually, contain all the topics that were covered in this class, the accompanying slides, exercise sheets, and frameworks for solving the programming exercises. (This table will be filled week by week.)

Week Topics Slides Exercise
1. Orga stuff
Introduction: definitions, applications, immersion, fidelity, presence,
2. Introduction: examples of the importance of fidelity and presence, measuring presence, behavior change using VR,
Lab meetings and assignments
3. Introduction: body ownership illusion, history, Milgram's continuum, augmented reality, the hype cycle.
Scenegraphs: immediate / retained mode, semantics of nodes and edges, inheritance, special issues with light sources, shared geometry (instancing), thread-safe scenegraphs, distributed scenegraphs, fields & routes concept, types of nodes, nodes and fields (entities and components), the Phong model for specification of the material, indexed face set, OBJ file format, FBX file format,
4. Scenegraphs: transformations, hierarchical transformations, behavior graph, data flow paradigm, execution model & event cascades, KV pool, distributed scenegraphs (again). PDF Assignment 1
5. Displays and stereo rendering: depth cues, human visual system and stereopsis, horopter and fusion area, VR displays / immersive displays / immersive projection technologies, multiplexing techniques for stereo images (polarization, shuttering, color filtering), PDF
6. Displays and stereo rendering: correct stereo projection, hypo- and hyper-stereo, issues with stereo rendering (depth aliasing, convergence-focus conflict, incorrect viewpoints, stereo violation, blur divergence, too much parallax), coherent virtual workspaces, automultiscopic display, PDF Assignment 2 Laggy jump'n run LOD meshes
7. Real-time rendering: latency and its sources, view-independent rendering, prioritized rendering, efficient memory layout for fast rendering, level-of-detail techniques, static/adaptive/psychophysiological LOD selection, predictive LOD selection, progressive meshes, view-dependent LODs, PDF
8. Real-time rendering: Foveated rendering
Input Devices: intrusiveness, degrees of freedom, multimodality, virtual trackball, isotonic vs isometric, tracking technologies, data gloves, locomotion devices, methods to classify input devices, logic devices.
9. Particle systems: Newton's Laws, dynamics vs kinematics, Euler integration, phase space, definition of particle systems, forces from physical effects, non-physical effects, collision handling, rendering of particle systems, alpha blending, PDF Assignment 3 Mass Spring System
10. Mass-spring systems: definition, single spring-damper element, explicit Euler integration, instability and error accumulation with explicit Euler integration, Runge-Kutta, Verlet integration, constraints, implicit integration, tangent stiffness matrix, comparison to explicit integration, mesh creation for volumetric objects, consistent collision response for volumetric mass-spring systems. PDF
11. Interaction techniques: Universal Interaction Tasks, approaches to design of user interfaces, the navigation task (wayfinding & locomotion), taxonomies as a design tool, abstract representation of the user for navigation, navigation metaphors (point-and-fly, scene-in-hand, two-handed, hands-free, walking in place, et al.), magic mirror, 3D navidget, user models: power law of practice, Hick's law, Fitts's law; 3D selection techniques, iso-/non-isomorphic techniques, control-display ratio, go-go technique, task decomposition of selection task, ray-based & cone-based techniques, flexible pointer, friction surface (bent ray), bubble cursor, depth ray, balloon selection, selection by progressive refinement: SQUAD, Disambiguation Canvas, Point-and-Zoom, Expand, object manipulation (grasping and moving), taxonomy of grasping, the manifold of hand postures, Natural User Interaction (NUI), PDF Assignment 4 Blocks Framework
12. Interaction techniques: general 3D interaction design principles, two-handed and multimodal interaction, physical props / tangible UIs, DOF separation/reduction: PRISM metaphor and 3D widgets, action-at-a-distance (examples: image plane interaction, voodoo dolls), proprioceptive interaction, world-in-miniature, magic lenses, redirecting the user, redirected walking and related techniques, body retargeting, amplified head rotation, spatial illusions, system control, menus, Nielsen's usability heuristics
Haptics: definitions, applications, devices, the haptic loop(s), the human haptic sense and human factors, simulation factors, haptic textures, the problems of buzzing and latency,
13. Haptics: intermediate representations, impedance/admittance-based approach, the surface contact point method, voxmap-pointshell method, friction in one contact point,
Collision detection: motivation, definitions, collision detection pipeline, broad/narrow phase, 3D grid for filtering potentially colliding pairs, plane-sweep technique, separating planes algorithm (for convex objects), Minkowski sums, intersection test for convex objects based on Minkowski sums,
14. Collision detection: hierarchical collision detection, bounding volume hierarchies, types of BV's, separating axis lemma for convex polyhedra, separating axis test (SAT), overlap test for k-DOP's, restricted boxtrees, construction of BVH's using the volume heuristic, inner sphere trees, sphere packings, proximity computation using ISTs, penalty forces using ISTs.
Sound rendering: motivation, human factors, mixing sound sources, image source method, beam tracing method, cell partitioning,

Screen Recordings of the Lecture as of WS 20/21

The videos are encoded with H.265/HEVC and should play fine with Safari and IE. With Chrome and Firefox, you might need to download the videos, or install a plugin/extension.

Introduction (340 MB)
Scene graphs and Game engines (250 MB),
Tutorial on Unreal Engine, (270 MB)
Display Technologies, Stereopsis, Stereo Rendering (250 MB)
Techniques for Real-Time Rendering (320 MB)
Principles of Input Devices (120 MB)
Particle Systems (140 MB)
Mass-Spring Systems (200 MB)
Interaction Techniques (450 MB)
Haptics (250 MB)
Collision Detection (250 MB)
Sound Rendering (90 MB)
Call for Theses

Note: all videos use the codec H265 (HEVC). (Saves about 50% disk space and bandwidth on average.) They work directly in the browsers Safari and IE (Edge), but not Chrome, and probably not Firefox (as of 2021). But you can always download the videos and play them using VLC.

You can find video recordings of the class taught in WS 19/20 here . The password is virtual2020.


Warning: these text books can only give you a general introduction to the field of VR! Most of the topics taught in class are not covered by any of these text books directly -- in fact, AFAIK there are some topics that are not covereed by any text book! Therefore, I recommend to attend class.

If you are thinking of buying some of these books, then I suggest to consider buying a used copy of them -- very often, you can find them at a fraction of the price of a new copy. The following are three very good internet sites for finding inexpensive used copies of books: abebooks, Booklooker, and ZVAB.

Help and documentation on the Unreal Engine:

Online Literature and Resources on the Internet

Literature and Resources on X3D/VRML

Since X3D/VRML is no longer the platform for the practical exercises in this course, I have demoted the links to X3D/VRML to this place.

Readings That Have Nothing to do With VR, but are Still Highly Recomended

Gabriel Zachmann
Last modified: Wed Aug 04 15:57:25 MDT 2021