Richard L. Grimsdale

Computer graphics techniques for modeling cloth

In this survey, we present a contemporary overview of cloth modeling techniques. 19 modeling techniques are summarized and categorized by their main theoretical method: geometrical, physical, or hybrid. The techniques within each category do not follow well-defined patterns. We therefore generally report each work independently according to the chronology of publication. At the end of the discussion of all techniques, we summarize their features in a table. We conclude by speculating on future research directions that could optimize the agreement between the requirements of visual realism and physical accuracy. The recommendations for future work consider the different goals in textile engineering and computer graphics.

The Image chip for high performance 3D rendering

The Image chip, which accelerates 3D rendering algorithms base on Bresenhams line drawing and Pinedas parallel polygon drawing algorithms, is discussed. With these algorithms, Image can directly draw lines, spans, and triangles in wireframe, hidden-line, and Gouraud-shading modes. Image also directly antialiases vectors or provides antialiasing information to enhance antialiasing of vectors or triangles. Images operation, separation into layers to maximize performance and simplify the input and output interfaces, and support of advanced rendering effects such as Phong shading and texture mapping are described. The designs of Images internal architecture, host interface, and memory interface are also described.<<ETX>>

A system for modelling and visualization of cloth material

Abstract This paper describes some developments in techniques for the visualization of the shapes of cloth materials when suspended at given points or draped over a rigid surface. The material is modelled by a set of energy equations, which takes the bending constant, density, elasticity, diagonal-to-axial strength ratio, and rigidity into account. The material will be in an equilibrium state when the energy is a minimum. The work described extends existing methods by employing a more efficient energy minimization technique and by reducing directional errors of the relaxation process. The technique has been implemented for a PC in the C language and generates data in a standard format suitable for display on commercial rendering software packages.

Performance of Space Subdivision Techniques in Ray Tracing

Whilst providing images of excellent quality, ray tracing is a computationally intensive task. The first part of this paper compares the speed‐up achieved in ray tracing using various space subdivision algorithms and discusses the implications of implementing the algorithms on parallel processing systems. The second part addresses the problem of building the data structure within the rendering process, a situation which occurs when the rendering process is parallelised and dynamic scenes are rendered. Greater performance can be achieved with dynamic structure building compared to creation of the structure prior to rendering. The dynamic building algorithm proposed reduces the building time and storage cost of space subdivision structures, and decreases the data structure creation‐render cycle time, thus enhancing image parallelism performance.

Approximation techniques for high performance texture mapping

Abstract Accurate perspective mapping in real-time requires costly division operations per pixel and therefore approximation techniques are often employed. These permit the mapping to be performed by interpolation, but generally with a significant set-up cost for the computation of the parameters. An efficient approximation technique which achieves good results with modest set-up requirements is presented. The technique uses Chebyshev control points to minimize errors.

GEOFF - A Geometrical Editor for Fold Formation

A new technique for modelling clothing is described in which the cloth layer is closely associated with the shape of the underlying flesh layer. The position of fold lines are determined on the basis of the distances between the layers. Folds are generated along the fold lines using a modified sinusoidal function. In contrast with techniques which are based on the physical properties of the material, the technique is fast and yet produces visually acceptable results. The technique has been incorporated within the GEOFF interactive editor which allows the user considerable control over fold generation.

REALISM: reusable elements for animation using local integrated simulation models

The REALISM animation system encapsulates behavioural control mechanisms within the objects in a scene, offering a single interface to both modelling and animation. Libraries of actors allow creative skills to be focused on scene development and not individual object control. The progress of an animation sequence is defined by a controlling script. Individual object behaviour is defined by rules and constraints, themselves dynamic entities that can modify their own behaviour during the animation. Each element controls its own destiny which is guided but not dictated by the script. To reduce the communication overhead caused by the inter-object dialogue necessary for collision detection, a two stage process is implemented. This consists of a bounding volume check as the first stage, and objects communicating to resolve collisions as the second stage. The algorithm ensures that the workload is distributed evenly throughout the objects, guaranteeing a maximum limit to the workload per object.<<ETX>>

MARTI: a multiprocessor architecture for ray tracing images

Multiprocessor systems are well suited to ray tracing, since each ray can be traced independently. However, the large databases required to model complex scenes create problems of data access. In this paper we propose a multiprocessor architecture for ray tracing which removes the need for duplication of the database at processor level. The database is held on a group processor basis, and resides in shared memory. Many of these groups, or clusters, can be replicated to form a highly parallel multiprocessing system. Results of a software simulation of the architecture are promising, indicating that a large number of processors per cluster is possible.

A multiple application graphics integrated circuit MAGIC II

This paper describes the design considerations for a polygon graphics geometry processor subsystem. The architecture for a Multiple Application Graphics Integrated Circuit (MAGIC II) is outlined, and low, medium and high performance system configurations using MAGIC II are discussed.

The HERO algorithm for ray-tracing octrees

An algorithm is presented for rapid traversal of octree data structures, in order to enhance the speed of ray tracing for scenes of high complexity. At each level of the octree, the algorithm generates the addresses of child voxels in the order they are penetrated by the ray. This requires only a few arithmetic operations and simple logical operations. A depth-first search of the tree is used to yield the first terminal voxel hit by the ray, thus hidden objects are not processed. The algorithm is designed specifically for implementation as HERO: A Hardware Enhancer for Ray-tracing Octrees.