This paper introduces a theoretical model for computing the scattering properties of participating media and translucent materials. The model takes as input a description of the components of a medium and computes all the parameters necessary to render it. These parameters are the extinction and scattering coefficients, the phase function, and the index of refraction, Our theory is based on a robust generalization of the Lorenz-Mie theory. Previous models using Lorenz-Mie theory have been limited to non-absorbing media with spherical particles such as paints and clouds. Our generalized theory is capable of handling both absorbing host media and non-spherical particles, which significantly extends the classes of media and materials that can be modeled. We use the theory to computer optical properties for different types of ice and ocean water, and we derive a novel appearance model for milk parameterized by the fat and protein contents. Our results show that we are able to match measured scattering properties in cases where the classical Lorez-Mie theory breaks down, and we can compute properties for media that cannot be measured using existing techniques in computer graphics.

A novel method for real-time simulation of indirect illumination is presented in this paper. The method, which we call direct radiance mapping (DRM), is based on basal radiance calculations and does not impose any restrictions on scene geometry or dynamics. This makes the method tractable for real-time rendering of arbitrary dynamic environments and for interactive preview of feature animations. Through DRM we simulate two diffuse reflections of light, but can also, in combination with traditional real-time methods for specular reflections, simulate more complex light paths. DRM is a GPU-based method, which can draw further advantages from upcoming GPU functionalities. The method has been tested for moderately sized scenes with close to real-time frame rates and it scales with interactive frame rates for more complex scenes.

This paper describes a method to determine correct shadow boundaries from an area light source using umbra and penumbra volumes. The light source is approximated by a circular disk as this gives a fast way to extrude the volumes. The method also gives a crude estimate of the visibility of the area light source as seen from a point in the shadow region. Instead of rendering the volumes to the stencil buffer, we use an extended shadow map - a so-called D-buffer, which among other things stores distances from the center of the light source to the umbra and penumbra volumes. The method is suited for implementation on most programmable hardware. Though some crude approximations are used in the visibility function, the method can be used to produce soft shadows with correct boundaries in real time.

No abstract available.

In this paper, we propose the use of the level-set method as the underlying technology of a volume sculpting system. The main motivation is that this leads to a very generic technique for deformation of volumetric solids. In addition, our method preserves a distance field volume representation. A scaling window is used to adapt the level-set method to local deformations and to allow the user to control the intensity of the tool. Level-set based tools have been implemented in an interactive sculpting system, and we show sculptures created using the system.

When choosing a graphics system for the run-time support component of a User Interface Management System (UIMS) several problems arise. Existing inputloutput models employed by graphics systems lack support for fine grain design control and for defining links between input and output. Furthermore, hardware maintainability is a problem. We have introduced a new inputloutput model, the symmetrical translation model (STM), which solves these problems through extensibility and symmetry. All input and output techniques are implemented by active objects which are specified using a high level notation. This notation allows the temporal and spatial composition of objects. A UIMS is being constructed at our department based upon this model.

Languages based on the event model are widely regarded as expressive and flexible notations for the specification of interactive graphical user interfaces. However, until now, they have only been used to specify and implement the dialogue control component of user interfaces.