Bent Dalgaard Larsen

Simulating photon mapping for real-time applications

This paper introduces a novel method for simulating photon mapping for real-time applications. First we introduce a new method for selectively redistributing photons. Then we describe a method for selectively updating the indirect illumination. The indirect illumination is calculated using a new GPU acceleratedfinal gathering method and the illumination is then stored in light maps. Caustic photons are traced on the CPU and then drawn using points in the framebuffer, and finally filtered using the GPU. Both diffuse and non-diffuse surfaces can be handled by calculating the direct illumination on the GPU and the photon tracing on the CPU. We achieve real-time frame rates for dynamic scenes.

Single-pass wireframe rendering

The depth offset is required because the procedure for rasterizing lines is not exactly the same as the one for rasterizing polygons. Consequently, when rasterizing a polygon edge as a line, a given fragment may have a depth value that is different from when the corresponding polygon itself is rasterized. This leads to stippling artefacts. However, adding an offset is not an ideal solution since this offset can result in disocclusions of lines that should be hidden. Moreover, there is usually stippling in any case near steep slopes in the mesh where a very large offset is sometimes required. The only real fix is a slope dependent offset but that tends to make disocclusion problems much worse. A few authors have proposed improved techniques, but either these are not intended for modern graphics hardware [Wang et al.] or they incur a performance hit [Herrel et al.].

Two methods for antialiased wireframe drawing with hidden line removal

Two novel and robust techniques for wireframe drawing are proposed. Neither suffer from the well-known artifacts associated with the standard two pass, offset based techniques for wireframe drawing. Both methods draw prefiltered lines and produce high-quality antialiased results without super-sampling. The first method is a single pass technique well suited for convex N-gons for small N (in particular quadrilaterals or triangles). It is demonstrated that this method is more efficient than the standard techniques and ideally suited for implementation using geometry shaders. The second method is completely general and suited for arbitrary N-gons which need not be convex. Lastly, it is described how our methods can easily be extended to support various line styles.

Boundary correct real-time soft shadows

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

Interactive shader development

Since the introduction of programmable graphics hardware, the creation of shader programs has played an increasingly important role in real-time graphics. Programming shaders is no trivial task, and this has led to the introduction of graphical shader editor tools. Using these tools, shaders are authored by connecting nodes and building a shade tree. In this paper we present an improved approach to real-time graphical shader authoring that removes several programming difficulties. Our approach automatically handles type- and geometrical space transformations by using intelligent variables as connection slots in the nodes. Our work also offers workflow enhancements for a more interactive creation process. When shaders are to be used in interactive applications such as games, they need to be optimized. Therefore we present a scheme for automatic optimization in two steps; first optimal code placement and second optimization of inserted transformations. Performance will be compared to hand-optimized programs.

Using cellular phones to interact with virtual environments

Distributed VR promises to change the way we work and collaborate [Singhal and Zyda 1999]. In this sketch we will extend the accessibility of the virtual world originally developed in [Larsen and Eriksen 1998] by introducing the use of the modern cellular phone as a platform for primitive interfaces to VR applications. We believe that our use of a cellular phone has led to the first completely pocketable platform for VR user interfaces.