Karsten Bormann

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Much effort has gone into exploring the concept of presence in virtual environments. One of the reasons for this is the possible link between presence and performance, which has also received a fair amount of attention. However, the performance side of this equation has been largely ignored. That is, without much discussion, researchers tend to equate(More)
We present a generic way of thinking about time machines from the view of a far away observer. In this model the universe consists of three (or more) regions: One containing the entrance of the time machine, another the exit and the remaining one(s) the rest of the universe. In the latter we know ordinary quantum mechanics to be valid and thus are able to(More)
The basic starting point of this paper is that ‘context’ constitutes most of the user interface when doing VR-related experiments, but even so one bases performance measures on only a few ‘active’ tasks. Thus, in order to meaningfully compare results obtained in vastly different experiments one needs to somehow ‘subtract’ the contribution to observables(More)
When developing virtual environments (VEs), most effort goes into developing the visuals. For many, the ideal is to create virtual worlds of photo-realistic quality or otherwise being of high fidelity. The purpose is to make the VE seem real to the user. This paper takes a closer look at subjects’ ratings of the visuals, and of the extent to which the VE(More)
We calculate the effective potentials for scalar, Dirac and YangMills fields in curved backgrounds using a new method for the determination of the heat kernel involving a re-summation of the SchwingerDeWitt series. Self-interactions are treated both to one loop order as usual and slightly beyond one-loop order by means of a mean-field approximation. The new(More)
In this paper visibility culling is integrated tightly with an octree data structure. This is done by slicing the frustum in such a way that the minimal distance from the eye to objects in a given frustum slice is twice the minimal eye to object distance of the previous slice. Then, if one has a fixed minimal detail size, i.e. a minimal spatial angle so(More)