This dissertation describes the principles of pen-and-ink illustration, and shows how a great number of them can be implemented as part of an automated rendering system. Illustration techniques in general, and pen-and-ink rendering in particular, offer great potential for creating effective images from CAD models. And with the computer's ability to manipulate increasingly large models, communicating complex information in an effective and comprehensible manner is becoming an important problem. However, this potential remains relatively untapped in the field of computer graphics. After discussing principles of traditional pen-and-ink rendering, this dissertation shows how the traditional graphics pipeline must be modified to support pen-andink rendering. Then, it introduces the new concept of prioritized stroke textures. Prioritized stroke textures form the central mechanism by which strokes are generated so as to both convey a certain texture, such as "bricks", and achieve a target tone simultaneously. Prioritized stroke textures also have the advantages of being resolution dependent

Figure 1: (Left) Uniform 512x512 shadow map and resulting image. (Right) The same with a perspective shadow map of the same size. Shadow maps are probably the most widely used means for the generation of shadows, despite their well known aliasing problems. In this paper we introduce perspective shadow maps, which are generated in normalized device coordinate space, i.e., after perspective transformation. This results in important reduction of shadow map aliasing with almost no overhead. We correctly treat light source transformations and show how to include all objects which cast shadows in the transformed space. Perspective shadow maps can directly replace standard shadow maps for interactive hardware accelerated rendering as well as in high-quality, offline renderers. CR Categories: I.3.3 [Computer Graphics]: Picture/Image Generation—Bitmap and framebuffer operations; I.3.7 [Computer

Visibility algorithms for walkthrough and related applications have grown into a significant area, spurred by the growth in the complexity of models and the need for highly interactive ways of navigating them. In this survey, we review the fundamental issues in visibility and conduct an overview of the visibility culling techniques developed in the last decade. The taxonomy we use distinguishes between point-based and from-region methods. Point-based methods are further subdivided into object and image-precision techniques, while from-region approaches can take advantage of the cell-and-portal structure of architectural environments or handle generic scenes.

The A-buffer (anti-aliased, area-averaged, accumulation buffer) is a general hidden surface mechanism suited to medium scale virtual memory computers. It resolves visibility among an arbitrary collection of opaque, transparent, and intersecting objects. Using an easy to compute Fourier window (box flter), it increases the effective image resolution many times over the Z-buffer, with a moderate increase in cost. The A-buffer is incorporated into the REYES 3-D rendering system at Lucasfilm and was used successfully in the "Genesis Demo " sequence in

This paper describes an object-space shadow generation algorithm for static polygonal environments illuminated by movable point light sources. The algorithm can be easily implemented on any graphics system that provides fast polygon scan-conversion and achieves near real-time performance for environments of modest size. It combines elements of two kinds of current shadow generation algorithms: two-pass object-space approaches and shadow volume approaches. For each light source a Binary Space Partitioning (BSP) tree is constructed that represents the shadow volume of the polygons facing it. As each polygon's contribution to a light source's shadow volume is determined, the polygon's shadowed and lit fragments are computed by filtering it down the shadow volume BSP tree. The polygonal scene with its computed shadows can be rendered with any polygon-based visible-surface algorithm. Since the shadow volumes and shadows are computed in object space, they can be used for further analysis of the scene. Pseudocode is provided, along with pictures and timings from an interactive implementation.

Virtual environment research has focused on interactive image generation and has largely ignored acoustic modeling for spatialization of sound. Yet, realistic auditory cues can complement and enhance visual cues to aid navigation, comprehension, and sense of presence in virtual environments. A primary challenge in acoustic modeling is computation of reverberation paths from sound sources fast enough for real-time auralization. We have developed a system that uses precomputed spatial subdivision and "beam tree" data structures to enable real-time acoustic modeling and auralization in interactive virtual environments. The spatial subdivision is a partition of 3D space into convex polyhedral regions (cells) represented as a cell adjacency graph. A beam tracing algorithm recursively traces pyramidal beams through the spatial subdivision to construct a beam tree data structure representing the regions of space reachable by each potential sequence of transmission and specular reflection even...

While large investments are made in sophisticated graphics hardware, most realistic rendering is still performed off-line using ray trace or radiosity systems. A coordinated use of hardware-provided bitplanes and rendering pipelines can, however, approximate ray trace quality illumination effects in a user-interactive environment, as well as provide the tools necessary for a user to declutter such a complex scene. A variety of common ray trace and radiosity illumination effects are presented using multi-pass rendering in a pipeline architecture. We provide recursive reflections through the use of secondary viewpoints, and present a method for using a homogeneous 2-D projective image mapping to extend this method for refractive transparent surfaces. This paper then introduces the Dual Z-buffer, or DZ-buffer, an evolutionary hardware extension which, along with current framebuffer functions such as stencil planes and accumulation buffers, provides the hardware platform to render non-refr...

this dissertation was conducted. Special thanks to Erin Shaw, Steve Westin, Pete Shirley, and John Hughes for carefully reading various portions of this work and offering detailed comments. Many thanks to my coauthors Julie Dorsey, Dave Kirk, Kevin Novins, David Salesin, Francois Sillion, Brian Sinits, Ken Torrance, and Steve Westin, from whom I have learned so much over the years, and to Pete Shirley, Dani Lischinski, Bill Gropp, and Jim Ferwerda for enumerable stimulating vi vii discussions. Thanks also to Ben Trumbore and Albert Dicruttalo for modeling and software support, to Dan Kartch for all the help with document preparation, to Jonathan Corson-Rikert, Ellen French, Linda Stephens, and Judy Smith for admin- istrative support, and to Hurf Sheldon for many years of cheerful and professional systems support. From my days at Apollo Computer, I'd like to thank A1 Lopez, Fabio Pettinati, Ken Severson, and Terry Lindgren for all their encouragement. Many fellow students and assorted friends have also helped and inspired me along the way, including Lenny Pitt, Mukesh Prasad, Michael Monks, Ken Musgrave, Andrew Glassner, Mimi and Noel Mateo, and Susan Vonderheide

Analytic visibility algorithms, for example methods which compute a subdivided mesh to represent shadows, are notoriously unrobust and hard to use in practice. We present a new method based on a generalized definition of extremal stabbing lines, which are the extremities of shadow boundaries. We treat scenes containing multiple edges or vertices in degenerate configurations, (e.g., collinear or coplanar). We introduce a robust ɛ method to determine whether each generalized extremal stabbing line is blocked, or is touched by these scene elements, and thus added to the line's generators. We develop robust blocker predicates for polygons which are smaller than ɛ. For larger ɛ values, small shadow features merge and eventually disappear. We can thus robustly connect generalized extremal stabbing lines in degenerate scenes to form shadow boundaries. We show that our approach is consistent, and that shadow boundary connectivity is preserved when features merge. We have implemented our algorithm, and show that we can robustly compute analytic shadow boundaries to the precision of our chosen ɛ threshold for non-trivial models, containing numerous degeneracies.

As an advanced form of visibility culling, occlusion culling detects hidden objects and prevents them from being rendered. An occlusion-culling algorithm that can effectively accelerate interactive graphics must simultaneously satisfy the following criteria: # Generality. It should be applicable to arbitrary models, not limited to architectural models or models with many large, polygonal occluders. # Significant Speed-up. It should not only be able to cull away large portions of a model, but do so fast enough to accelerate rendering. # Portability and Ease of Implementation. It should contain as few assumptions as possible on special hardware support. It must also be robust (i.e. insensitive to floating-point errors). Based on proper problem decomposition and efficient representations of cumulative occlusion, this dissertation presents algorithms that sa...