11741283
Smooth interpolation of orientations with angular velocity constraints using quaternions
In this paper we present methods to smoothly interpolate 
orientations, given N rotational key frames of an 
object along a trajectory. The methods allow the user 
to impose constraints on the rotational path, such as 
the angular velocity at the endpoints of the trajectory. 
 
We convert the rotations to quaternions, and then 
spline in that non-Euclidean space. Analogous to the 
mathematical foundations of flat-space spline curves, 
we minimize the net “tangential acceleration” of the 
quaternion path. We replace the flat-space quantities 
with curved-space quantities, and numerically solve the 
resulting equation with finite difference and optimization 
methods.
6983775
Modeling surfaces of arbitrary topology using manifolds
Manifolds describe complicated objects that are locally $\Re\sp{n}$ by defining a set of overlapping maps from the object to $\Re\sp{n}$. In this thesis we present a general technique for inverting that process: we define a complicated object from a set of overlapping subsets of $\Re\sp{n}$. We first present a constructive definition that describes how to perform such a construction in general. We then apply this construction to the particular problem of defining surfaces of arbitrary topology. The surface is built in two steps: we build a manifold with the correct topology then embed the manifold into $\Re\sp3$ using traditional spline techniques. The surface inherits many of the properties of B-splines: local control, a compact representation, and guaranteed continuity of arbitrary degree. The surface is specified using a polyhedral control mesh instead of a rectangular one; the resulting surface approximates the polyhedral mesh much as a B-spline approximates its rectangular control mesh. Like a B-spline, the surface is a single, continuous object.
2239491
Voice as sound: using non-verbal voice input for interactive control
We describe the use of non-verbal features in voice for direct control of interactive applications. Traditional speech recognition interfaces are based on an indirect, conversational model. First the user gives a direction and then the system performs certain operation. Our goal is to achieve more direct, immediate interaction like using a button or joystick by using lower-level features of voice such as pitch and volume. We are developing several prototype interaction techniques based on this idea, such as "control by continuous voice", "rate-based parameter control by pitch," and "discrete parameter control by tonguing." We have implemented several prototype systems, and they suggest that voice-as-sound techniques can enhance traditional voice recognition approach.
6477925
Constructive solid geometry for polyhedral objects
Constructive Solid Geometry (CSG) is a powerful way of describing solid objects for computer graphics and modeling. The surfaces of any primitive object (such as a cube, sphere or cylinder) can be approximated by polygons. Being abile to find the union, intersection or difference of these objects allows more interesting and complicated polygonal objects to be created. The algorithm presented here performs these set operations on objects constructed from convex polygons. These objects must bound a finite volume, but need not be convex. An object that results from one of these operations also contains only convex polygons, and bounds a finite volume; thus, it can be used in later combinations, allowing the generation of quite complicated objects. Our algorithm is robust and is presented in enough detail to be implemented.
7017581
Multi-finger cursor techniques
The mouse cursor acts as a digital proxy for a finger on graphical displays. Our hands, however, have ten fingers and many degrees of freedom that we use to interact with the world. We posit that by creating graphical cursors that reflect more of the hand's physical properties, we can allow for richer and more fluid interaction. We demonstrate this idea with three new cursors that are controlled by the user's fingers using a multi-point touchpad. The first two techniques allow for simultaneous control of several properties of graphical objects, while the third technique makes several enhancements to object selection.
795737
Navigating documents with the virtual scroll ring
We present a technique for scrolling through documents that is simple to implement and requires no special hardware. This is accomplished by simulating a hardware scroll ring--a device that maps circular finger motion into vertical scrolling. The technique performs at least as well as a mouse wheel for medium and long distances, and is preferred by users. It can be particularly useful in portable devices where screen-space and space for peripherals is at a premium.
40790646
A Type Specialisation Tutorial
The essence of partial evaluation is beautifully simple: we just take a program, together with values of some of its inputs; we perform the operations that depend only on known inputs, build a new program from the other operations, and finally obtain a residual program which solves the same problem as the original for a subclass of the cases. Work by Neil Jones and his group over the past decade and a half has demonstrated just how powerful this simple idea really is.
13883306
Implementing Projection-based Strictness Analysis
Projection-based backwards strictness analysis has been understood for some years. Surprisingly, even though the method is fairly simple and quite general, no reports of its implementation have appeared. This paper describes ideas underlying our prototype implementation of the analysis for a simple programming language. The implementation serves as a case study before applying the method in the Glasgow Haskell compiler.
40264513
Avoiding Unnecessary Updates
Graph reduction underlies most implementations of lazy functional languages, allowing separate computations to share results when sub­ terms are evaluated. Once a term is evaluated, the node of the graph representing the computation is updated with the value of the term. How­ ever, in many cases, no other computation requires this value, so the up­ date is unnecessary. In this paper we take some steps towards an analysis for determining when these updates may be omitted.
29935552
Optimal design of checksum-based checkers for fault detection in linear analog circuits
Traditionally, built-in self-test (BIST) techniques have assumed access to only the input and output nodes of the circuit under test (CUT). It has been shown earlier, that checksum-based checkers can be designed to perform on-line fault detection in linear analog circuits using access to certain internal nodes of CUT. In this paper, we address the problem of optimizing the checker circuitry to maximize the detectability of faults in CUT. The above optimization problem is solved as a linear programming problem. The resulting checker can be used to perform both BIST of CUT and on-line error detection as well. Faults in the checker hardware are taken into account during the checker optimization process.
2210
Length-Based Attacks for Certain Group Based Encryption Rewriting Systems
In this note, we describe a probabilistic attack on public key cryptosystems based on the word/conjugacy problems for finitely presented groups of the type proposed recently by Anshel, Anshel and Goldfeld. In such a scheme, one makes use of the property that in the given group the word problem has a polynomial time solution, while the conjugacy problem has no known polynomial solution. An example is the braid group from topology in which the word problem is solvable in polynomial time while the only known solutions to the conjugacy problem are exponential. The attack in this paper is based on having a canonical representative of each string relative to which a length function may be computed. Hence the term length attack. Such canonical representatives are known to exist for the braid group.