As newer and more sophisticated imagery collection systems rapidly increase the volume of imagery requiring thorough exploitation, the need for imagery analysts to acquire and maintain expertise increases accordingly....
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Graphical search is a technique for finding all instances of a graphical pattern in a synthetic picture in which objects are regions bounded by lines and curves. The pattern may describe shape, color and other propert...
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Graphical search is a technique for finding all instances of a graphical pattern in a synthetic picture in which objects are regions bounded by lines and curves. The pattern may describe shape, color and other properties. Matched objects may be allowed to differ from the pattern in rotation and scale or may differ in shape by a specified tolerance. Graphical replace is a technique for replacing the shape, color, or other properties of matched objects with new properties described in a replacement pattern. Combined, the two techniques are similar to textual search and replace in text editors. Graphical search and replace can be used to make global changes to illustrations with repetitive patterns, independent of the means used to make those patterns. It can also be used to create a class of iterative or recursive shapes that can be specified by replacement rules.
Symbolic manipulation is commonly used in theoretical physics. Compilers for language like REDUCE are usually large and thus suited for mainframes only. The need for simple manipulation of polynomials in many variable...
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Symbolic manipulation is commonly used in theoretical physics. Compilers for language like REDUCE are usually large and thus suited for mainframes only. The need for simple manipulation of polynomials in many variables using easily accessible techniques led the first author to design and implement a language FORTRAN/P which is standard FORTRAN with two new types VARIABLE and POLYNOM. Nowadays micros have changed the situation and a completely new system POLYMAN for interactive polynomial handling has been developed.
Refinement is usually advocated as a means of gaining finer control over a spline curve or surface during editing. For curves, refinement is a local process. It permits the change of control vertices and subsequent ed...
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Refinement is usually advocated as a means of gaining finer control over a spline curve or surface during editing. For curves, refinement is a local process. It permits the change of control vertices and subsequent editing of fine detail in one region of the curve while leaving control vertices in other regions unaffected. For tensor-product surfaces, however, refinement is not local in the sense that it causes control vertices far from a region of interest to change as well as changing the control vertices that influence the region. However, with some care and understanding it is possible to restrict the influence of refinement to the locality at which an editing effect is desired. We present a method of localizing the effect of refinement through the use of overlays, which are hierarchically controlled subdivisions. We also introduce two editing techniques that are effective when using overlays: one is direct surface manipulation through the use of edit points and the other is offset referencing of control vertices.
The display of three-dimensional medical data is becoming more common, but current display hardware and image rendering algorithms do not generally allow real-time interaction with the image by the user. Real-time int...
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Certain Catmull-Rom splines interpolate their control vertices and share many properties such as affine invariance global smoothness and local control with B-spline curves;they are therefore of possible interest to co...
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Certain Catmull-Rom splines interpolate their control vertices and share many properties such as affine invariance global smoothness and local control with B-spline curves;they are therefore of possible interest to computer aided design. It is shown that another property a class of Catmull-Rom splines shares with B-spline curves is that both schemes possess a simple recursive evaluation algorithm. The Catmull-Rom evaluation algorithm is constructed by combining the de Boor algorithm for evaluating B-spline curves with Neville's algorithm for evaluating Lagrange polynomials. The recursive evaluation algorithm for Catmull-Rom curves allows rapid evaluation of these curves by pipelining with specially designed hardware. It facilitates the development of new, related curve schemes which may have useful shape parameters for altering the shape of the curve without moving the control vertices. It may also be used for constructing transformations to Besier and B-spline form.
We consider the problem of converting boundary representations of polyhedral objects into constructive-solid-geometry (CSG) representations. The CSG representations for a polyhedron P are based on the half-spaces supp...
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We consider the problem of converting boundary representations of polyhedral objects into constructive-solid-geometry (CSG) representations. The CSG representations for a polyhedron P are based on the half-spaces supporting the faces of P. For certain kinds of polyhedra this problem is equivalent to the corresponding problem for simple polygons in the plane. We give a new proof that the interior of each simple polygon can be represented by a monotone Boolean formula based on the half-planes supporting the sides of the polygon and using each such half-plane only once. Our contribution is an efficient and practical O(n log n) algorithm for doing this boundary-to-CSG conversion for a simple polygon of n sides. We also prove that such formulae do not always exist for general polyhedra in three dimensions.
Designing a complex system such as a control, automation or electronic system most engineering activities involve graphical representations for the different design and modelling stages. Starting the design cycle the ...
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Designing a complex system such as a control, automation or electronic system most engineering activities involve graphical representations for the different design and modelling stages. Starting the design cycle the structure and function of the system has to be specified. For the ease of imagination and decision the difficult interrelations between system components and subfunctions are frequently depicted by graphical schematics and diagrams. In this paper we introduce the idea and basic functions of a general purpose computer Aided Schematics (CAS) system, that may assist efficiently all schematics-based processes ranging from interactive to completely automatic drawing including the interfaces to further data processing. We discuss the benefits of the CAS approach as rapid generation and updating of correct and consistent graphics and its impact on the whole design and documentation cycle. Furthermore, some of the intricate, mainly graphtheoretical optimization problems inherent in the computer generated layout of schematic drawings are addressed. Finally, we outline the possible application of CAS techniques to different engineering disciplines, where graphical programming and documentation of programmable controllers (PC’s) is believed to be a profitable domain. First encouraging experience in the automatic documentation of complex control programs is reported on.
A behavioral and logic simulation system which uses extensive optimization and compilation techniques to obtain high performance is described. It incorporates data-flow analysis to optimize the evaluation of unordered...
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A behavioral and logic simulation system which uses extensive optimization and compilation techniques to obtain high performance is described. It incorporates data-flow analysis to optimize the evaluation of unordered assignment statements that define a hardware structure, and to extract clocking rules. An integral code generator produces efficient assembly code for three different machines, and an associated run-time library provides a flexible interactive debugging environment.< >
Trimmed non-uniform rational B-splines have become a very useful surface representation form in the mechanical CAD industry. Previous rendering methods use the de Boor algorithm to evaluate the surface at equal increm...
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Trimmed non-uniform rational B-splines have become a very useful surface representation form in the mechanical CAD industry. Previous rendering methods use the de Boor algorithm to evaluate the surface at equal increments in parameter space. This yields polygons which are then rendered. Alternatively the Oslo algorithm and Boehm's knot insertion algorithms are used in a subdivision approach. A new method is presented for rendering trimmed NURB surfaces of arbitrary order using the adaptive forward differencing (AFD) technique. This method extends the AFD technique to higher order, efficiently computes the basis matrix for each span, calculates the shading approximation functions for rational surfaces, and trims and image maps NURB surfaces. Trimming is accomplished by using AFD to scan convert the trimming curves in parameter space, thus producing the intersection points between the trim curves and an isoparametric curve across the surface. A winding rule is used to determine the regions bounded by the curve which are then rendered with AFD. The method is suitable for both hardware and software implementations;however, higher order surfaces require high precision due to the forward difference nature of the algorithm.
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