A new unbiased sampling approach is presented, which allows the direct illumination from disk and cylinder light sources to be sampled with a uniform probability distribution within their solid angles, as seen from each illuminated point. This approach applies to any form of global illumination path tracing algorithm (forward or bidirectional), where the direct illumination integral from light sources needs to be estimated. We show that taking samples based on the solid angle of these two light sources leads to improved estimates and reduced variance of the Monte Carlo integral for direct illumination. This work follows from previously known unbiased methods for the solid angle sampling of triangular and rectangular light sources and extends the class of lights that can be rendered with these improved sampling algorithms.

We present an accurate and efficient method to generate samples based on a Poisson-disk distribution. This type of distribution, because of its blue noise spectral properties, is useful for image sampling. It is also useful for multidimensional Monte Carlo integration and as part of a procedural object placement function. Our method extends trivially from 2D to 3D or to any higher dimensional space. We demonstrate results for up to four dimensions, which are likely to be the most useful for computer graphics applications. The method is accurate because it generates distributions with the same statistical properties of those generated with the brute-force dart-throwing algorithm, the archetype against which all other Poisson-disk sampling methods are compared. The method is efficient because it employs a spatial subdivision data structure that signals the regions of space where the insertion of new samples is allowed. The method hasO(NlogN) time and space complexity relative to the total number of samples. The method generates maximal distributions in which no further samples can be inserted at the completion of the algorithm. The method is only limited in the number of samples it can generate and the number of dimensions over which it can work by the available physical memory.

Hypertextures are a useful modelling tool in that they can add three-dimensional detail to the surface of otherwise smooth objects. Hypertextures can be rendered as implicit surfaces, resulting in objects with a complex but well defined boundary. However, representing a hypertexture as an implicit surface often results in many small parts being detached from the main surface, turning an object into a disconnected set. Depending on the context, this can detract from the realism in a scene where one usually does not expect a solid object to have clouds of smaller objects floating around it. We present a topology correction technique, integrated in a ray casting algorithm for hypertextured implicit surfaces, that detects and removes all the surface components that have become disconnected from the main surface. Our method works with implicit surfaces that are C2 continuous and uses Morse theory to find the critical points of the surface. The method follows the separatrix lines joining the critical points to isolate disconnected components.

Abstract A simple and elegant method is presented to perform anti‐aliasing in raytraced images. The method uses stratified sampling to reduce the occurrence of artefacts in an image and features a B‐spline filter to compute the final luminous intensity at each pixel. The method is scalable through the specification of the filter degree. A B‐spline filter of degree one amounts to a simple anti‐aliasing scheme with box filtering. Increasing the degree of the B‐spline generates progressively smoother filters. Computation of the filter values is done in a recursive way, as part of a sequence of Newton‐Raphson iterations, to obtain the optimal sample positions in screen space. The proposed method can perform both anti‐aliasing in space and in time, the latter being more commonly known as motion blur. We show an application of the method to the ray casting of implicit procedural surfaces.

JPEG 2000 is a flexible standard for coding many different types of images. This flexibility will be increased in the near future with the JP3D standard, an extension of JPEG 2000 to three dimensions. This paper presents a set of techniques to code three-dimensional textured parametric surfaces, common in Computer Graphics applications, using JPEG 2000 and possibly using extensions from the newer JP3D standard. These coding techniques generate compressed files of much smaller size than conventional file formats for storing three-dimensional objects. This is because the proposed coding techniques are able to exploit the strong correlation that exists between neighboring surface points in a parametric representation. Furthermore, it is possible to encode parametric surfaces which change through time, something that is not available in many conventional file formats. The reversible compression mode of JPEG 2000 ensures that threedimensional surfaces can be recovered without error after decompression. This is an important requirement for surfaces used in medical imaging, for example. This paper will demonstrate how a large variety of surfaces can be coded with JPEG 2000. The techniques presented here impose only one, but important, constraint on the surfaces: they must obey a parametric representation.