Wagner Toledo Corrêa

Non-photorealistic virtual environments

We describe a system for non-photorealistic rendering (NPR) of virtual environments. In real time, it synthesizes imagery of architectural interiors using stroke-based textures. We address the four main challenges of such a system — interactivity, visual detail, controlled stroke size, and frame-to-frame coherence — through image based rendering (IBR) methods. In a preprocessing stage, we capture photos of a real or synthetic environment, map the photos to a coarse model of the environment, and run a series of NPR filters to generate textures. At runtime, the system re-renders the NPR textures over the geometry of the coarse model, and it adds dark lines that emphasize creases and silhouettes. We provide a method for constructing non-photorealistic textures from photographs that largely avoids seams in the resulting imagery. We also offer a new construction, art-maps, to control stroke size across the images. Finally, we show a working system that provides an immersive experience rendered in a variety of NPR styles.

Texture mapping for cel animation

We present a method for applying complex textures to hand-drawn characters in cel animation. The method correlates features in a simple, textured, 3-D model with features on a hand-drawn figure, and then distorts the model to conform to the hand-drawn artwork. The process uses two new algorithms: a silhouette detection scheme and a depth-preserving warp. The silhouette detection algorithm is simple and efficient, and it produces continuous, smooth, visible contours on a 3-D model. The warp distorts the model in only two dimensions to match the artwork from a given camera perspective, yet preserves 3-D effects such as self-occlusion and foreshortening. The entire process allows animators to combine complex textures with hand-drawn artwork, leveraging the strengths of 3-D computer graphics while retaining the expressiveness of traditional handdrawn cel animation. CR Categories: I.3.3 and I.3.7 [Computer Graphics].

Visibility-based prefetching for interactive out-of-core rendering

We present a new visibility-based prefetching algorithm for interactive out-of-core rendering of large models on an inexpensive PC. Using an approximate visibility technique, we can very accurately and efficiently determine which geometry will be visible in the near future and prefetch that geometry from disk before it must be rendered. Our prefetching algorithm is a key part of a visualization system capable of rendering a 13-million triangle model with 99% accuracy at interactive frame rates. Our prefetching algorithm is the first of its kind to be based on a from-point visibility technique, and enables interactive rendering on a commodity PC, as opposed to expensive high-end graphics workstations or parallel machines.

Towards point-based acquisition and rendering of large real-world environments

This paper describes a pipeline for the acquisition and rendering of large real-world environments. In the acquisition phase, we use a laser rangefinder to capture the geometry of an environment, and a digital camera to capture its colors. In the rendering phase, we use a cluster of commodity PCs to render high-resolution images of the environment at interactive frame rates. In this paper, we describe in detail our scanning hardware, the tools we use to minimize the acquisition artifacts in the 3D scans, the procedure to register the scans to each other, and how to map colors from a photograph to a scan. We also present a sequential, out-of-core rendering approach that uses multiple threads to overlap rendering, visibility computation, and disk operations. Finally, we show how to use the sequential rendering approach as a building block for a parallel rendering system that uses a cluster of PCs to drive a high-resolution, multi-projector display wall. Our acquisition approach allows us to capture environments that would be extremely difficult to model by hand, and our rendering approach allows us to use inexpensive PCs, instead of high-end graphics workstations, to visualize those environments at interactive frame rates.

Real Time Interactive Massive Model Visualization

Real-time interaction with complex models has always challenged interactive computer graphics. Such models can easily contain gigabytes of data. This tutorial covers state-ofthe-art techniques that remove current memory and performance constraints. This allows a fundamental change in visualization systems: users can interact with huge models in real time.

Visualizing spatial and temporal variability in coastal observatories

In this paper, we describe a set of 3D and 4D visualization tools and techniques for CORIE, a complex environmental observation and forecasting system (EOFS) for the Columbia River. The Columbia River, a complex and highly variable estuary, is the target of numerous cross-disciplinary ecosystem research projects and is at the heart of multiple sustainable development issues with long reaching implications for the Pacific Northwest. However, there has been until recently no comprehensive and objective system available for modeling this environment, and as a consequence, researchers and agencies have had inadequate tools for evaluating the effects of natural resource management decisions. CORIE was designed to address this gap and is a major step towards the vision of a scalable, multi-use, real-time EOFS. Although CORIE already had a rich set of visualization tools, most of them produced 2D visualizations and did not allow for interactive visualization. Our work adds advanced interactive 3D tools to CORIE, which can be used for further inspection of the simulated and measured data.