Navigation is one of the most fundamental tasks in virtual environments, that requires timely collision detection and collision avoidance mechanisms. It was shown that when navigation is constrained to moving on a terrain, the problem of collision detection can be reduced from 3D to 2D case, by encoding all 3D objects that constitute travel obstacles into a terrain elevation image map, using a dedicated color. The original approach was developed for static environments explored by a single user. The new improved system, presented in this article, is capable of processing collisions for multiple travelers, including autonomous agents, in dynamically changing environments. Implementation details of the new system are presented, with a number of case studies and a discussion of future work.

Terrain elevation maps can be efficiently used for real-time collision processing for ground-bound travelers Maps. We extend this approach to handle objects that may fly freely in 3D space. The new algorithm makes effective use of allocated terrain image memory and does not require extra storage. It is easy to implement into any travel processing system.

Mouse, joystick and keyboard controls in 3D games have long since become a second nature for generations of garners. Recent advances in webcam-based tracking technologies made it easy to bring natural human motions and gestures into play. However, video tracking is a CPU-intensive process, which may have a negative impact on game performance. We measured this impact for different types of 3D content and found it to be minimal, on multi-core platforms. We provide details on implementation and evaluation of our system. Also, we suggest several examples how natural motion can be used in 3D games.

Natural head motion is the key component in Virtual Reality systems where users are immersed via personal eyewear. The advent of webcam tracking technologies made head motion available on every desktop, for any 3D game, calling for revised methods of handling user head motion in new, non-immersive settings. We present several novel techniques of using head motion in 3D social games. We show that head tracking is not only a useful, but also an enabling technology, that creates new means of interaction between players, makes gameplay more personal and game controls more flexible.

Life on Earth has many forms and every life form has its own version of reality, as reflected in the eyes of the viewer. These worlds are as real as the one that we know and all of them are equally fascinating. The multiverse of such "animal realities" can be explored in Virtual Reality, as described in this concept work.

In Virtual Environments (VE), users are often facing tasks that involve direct manipulation of virtual objects at close distances, such as touching, grabbing, placement. In immersive systems that employ head-mounted displays these tasks could be quite challenging, due to lack of convergence of virtual cameras.

Reliable and unobtrusive eye tracking remains a technical challenge for immersive virtual environment, especially when Head Mounted Displays (HMD) are used for visualization and users are allowed to move freely in the environment. In this work, we provide experimental evidence that gaze direction can be safely approximated by user head rotation, in HMD-based Virtual Reality (VR) applications, where users actively interact with the environment. We discuss the application range of our approach and consider possible extensions.

Developers are the first people who come to an empty world and make it habitable. In online virtual worlds, developers are 3D artists, architects, cloth designers and other talented and enthusiastic individuals with a passion for 3D modeling. Their joint creative efforts make virtual worlds possible.

A virtual hand metaphor remains by far the most popular technique for direct object manipulation in immersive Virtual Reality (VR). The utility of the virtual hand depends on a user's ability to see it correctly in stereoscopic 3D, especially in tasks that require continuous, precise hand-eye coordination.

We propose a novel framework for monitoring and evaluating user travel activity in Virtual Reality (VR), in real time. Using this framework, we examined how users progressed in mastering two common travel techniques: steering and target-based relocation. We identified three groups of subjects with distinctly different learning patterns, which we called advancing, neutral and regressing learners. In this paper, we explain our evaluation method in detail, describe the experimental study, discuss the results and practical applications of our findings.

Two common limitations of modern Head Mounted Displays (HMD): the narrow field of view and limited dynamic range, call for rendering techniques that can circumvent or even take advantage of these factors. We describe a simple practical method of enhancing visual response from HMDs by using view-dependent control over lighting. One example is provided for simulating blinding lights in dark environments.

Mixing real and virtual elements into one environment often involves creating geometry models of physical objects. Traditional approaches include manual modeling by 3D artists or use of dedicated devices. Both approaches require special skills or special hardware and may be costly. We propose a new method for fast semi-automatic 3D geometry acquisition, based upon unconventional use of motion tracking equipment. The proposed method is intended for quick surface prototyping for virtual, augmented and mixed reality applications where quality of visualization of objects is not required or is of low priority.

This paper presents a complete design environment that explores the modeling capabilities of convolution surfaces and puts them into practice. The design system includes a number of implicit primitives and modeling techniques that allow objects to be created by sculpting their surfaces at all levels of detail. All the techniques are illustrated using models of marine life forms and other objects of organic origin. Implementation and efficiency issues are discussed.

A ray‐tracing algorithm is described for rendering implicit surfaces formed with C1‐continuous bounded functions f(x, y, z). This class of functions includes such popular implicit models as blobby molecules, metaballs, soft objects and convolution surfaces. The algorithm employs analytical methods only, which makes it fast, robust, and numerically stable. An earlier version of this work was presented at the 3rd International Workshop on Implicit Surfaces held in Seattle in 1998.

Implicit surfaces obtained by convolution of multi‐dimensional primitives with some potential function, are a generalisation of popular implicit surface models: blobs, metaballs and soft objects. These models differ in their choice of potential function but agree upon the use of underlying modelling primitives, namely, points. In this paper a method is described for modelling and rendering implicit surfaces built upon an expanded set of skeletal primitives: points, line segments, polygons, arcs and planes. An analytical solution to the convolution is described. This solution offers a more accurate and robust representation of the resultant implicit surface than previous methods. An algorithm for ray‐tracing the surfaces formed through convolution of any combination of these primitives is also outlined.