Wolfgang Heidrich

Applications of pixel textures in visualization and realistic image synthesis

With fast3D graphicsbecomingmoreandmoreavailableevenon low endplatforms,thefocusin developingnew graphicshardware is beginning to shift towardshigher quality renderingand additional functionality insteadof simply higher performanceimplementationsof the traditionalgraphicspipeline. On this searchfor improved quality it is importantto identify a powerful set of orthogonalfeaturesto be implementedin hardware,which canthen beflexibly combinedto form new algorithms. Pixel texturesareanOpenGLextensionby SiliconGraphicsthat fits into this category. In this paper , we demonstratethebenefitsof thisextensionby presentingseveraldifferentalgorithmsexploiting its functionalityto achievehighquality, highperformancesolutions for a variety of differentapplicationsfrom scientificvisualization andrealisticimagesynthesis.Weconcludethatpixel texturesarea valuable,powerful featurethatshouldbecomea standardin future graphicssystems. CR Categories: I.3.3 [Computer Graphics]: Picture/Image Generation—Bitmapand framebuffer operationsI.3.3 [Computer Graphics]: Picture/ImageGeneration—Displayalgorithms I.3.6 [ComputerGraphics]: Methodologyand Techniques—Standards I.3.7 [Computer Graphics]: Three-DimensionalGraphics and Realism—Color , Shading,Shadowing andTexture

View-independent environment maps

Environment maps are widely used for approximating reflections in hardware-accelerated rendering applications. Unfortunately, the parameterizations for environment maps used in today’s graphics hardware severely undersample certain directions, and can thus not be used from multiple viewing directions. Other parameterizations exist, but require operations that would be too expensive for hardware implementations. In this paper we introduce an inexpensive new parameterization for environment maps that allows us to reuse the environment map for any given viewing direction. We describe how, under certain restrictions, these maps can be used today in standard OpenGL implementations. Furthermore, we explore how OpenGL could be extended to support this kind of environment map more directly. CR Categories: 1.3.1 [Computer Graphics]: Hardware Architecture-Graphics processors; 1.3.3 [Computer Graphics]: Picture/Image Generation-Bitmap and framebuffer operations; 1.3.6 [Computer Graphics]: Methodology and Techniques--Standards 1.3.7 [Computer Graphics]: ThreeDimensional Graphics and Realism-Color, Shading, Shadowing and Texture 1.4.1 [Image Processing and Computer Vision]: Digitization and Image Capture ~-Sampling

Interactive maximum projection volume rendering

Maximum projection is a volume rendering technique that, for each pixel, finds the maximum intensity along a projector. For certain important classes of data, this is an approximation to summation rendering which produces superior visualizations. We show how maximum projection rendering with additional depth cues can be implemented using simple affine transformations in object space. This technique can be used together with 3D graphics libraries and standard graphics hardware, thus allowing interactive manipulations of the volume data. The algorithm presented allows for a wide range of tradeoffs between interactivity and image quality.

Sampling procedural shaders using affine arithmetic

Procedural shaders have become popular tools for describing surface reflectance functions and other material properties. In comparison to fixed resolution textures, they have the advantage of being resolution-independent and storage-efficient.nWhile procedural shaders provide an interface for evaluating the shader at a single point, it is not easily possible to obtain an average value of the shader together with accurate error bounds over a finite area. Yet the ability to compute such error bounds is crucial for several interesting applications, most notably heirarchical area sampling for global illumination, using the finite element approach, and for generation of textures used in interactive computer graphics.nUsing affine arithmetic for evaluating the shader over a finite area yields a tight, conservative error interval for the shader function. Compilers can automatically generate code for utilizing affine arithmetic from within shaders implemented in a dedicated language such as the RenderMann shading language.

A model for anisotropic reflections in open GL

anisotropic surfaces. Often, this anisotropy is caused by a micro structure, in which long, thin features are aligned in one predominant direction. For example, brushed metal objects have been polished in such a way that there are a lot of parallel scratches in the surface. On CDs and records, the micro structure is given by the tracks carrying the music or data, and woven cloth consists of fibers oriented in certain directions.

The SFB 603 — Model Based Analysis and Visualization of Complex Scenes and Sensor Data

This special research area combines visualization and interpretation of sensor data by exploring the central subjects “models”, “optimization”, “hierarchies”, and “data fusion”. This article describes the structural and thematic organization of the research project and illustrates first results of one sub-project as an example.