Non-photorealistic volume rendering using stippling techniques

Journal ArticleSimulating hand-drawn illustration techniques can succinctly express information in a manner that is communicative and informative. We present a framework for an interactive direct volume illustration system that simulates traditional stipple drawing. By combining the principles of artistic and scientific illustration, we explore several feature enhancement techniques to create effective, interactive visualizations of scientific and medical datasets. We also introduce a rendering mechanism that generates appropriate point lists at all resolutions during an automatic preprocess, and modifies rendering styles through different combinations of these feature enhancements. The new system is an effective way to interactively preview large, complex volume datasets in a concise, meaningful, and illustrative manner. Volume stippling is effective for many applications and provides a quick and efficient method to investigate volume models

Curvature-based transfer functions for direct volume rendering: methods and applications

Journal ArticleDirect volume rendering of scalar fields uses a transfer function to map locally measured data properties to opacities and colors. The domain of the transfer function is typically the one-dimensional space of scalar data values. This paper advances the use of curvature information in multi-dimensional transfer functions, with a methodology for computing high-quality curvature measurements. The proposed methodology combines an implicit formulation of curvature with convolution-based reconstruction of the field. We give concrete guidelines for implementing the methodology, and illustrate the importance of choosing accurate filters for computing derivatives with convolution. Curvature-based transfer functions are shown to extend the expressivity and utility of volume rendering through contributions in three different application areas: nonphotorealistic volume rendering, surface smoothing via anisotropic diffusion, and visualization of isosurface uncertainty

Volume painting: incorporating volumetric rendering with line integral convolution (LIC)

This thesis presents an expressive (non-photorealistic) rendering approach created by combining volumetric rendering techniques with the Line Integral Convolution (LIC) in 3D space. Although some techniques that combine volume rendering with the LIC have been introduced in computer graphics, they are mainly used for the scientific visualization fields, such as the visualization of 3D fluid fields. Unlike earlier research, we will focus on artistic representation, which is significantly different than scientific visualization research. We will implement a brush-stroke effect on the implicit surfaces by using the LIC. The implicit surfaces are described as volume datasets that are created by the voxelization of triangular meshes. To acquire smearing effects on the surface we convolve along the vector fields with the densities of the voxels of the datasets. These vector fields are defined by users as texture maps. The final images are rendered with volume ray casting, integrating colors and densities of voxels with Perlin noise along vector fields. The Perlin noise provides randomness and allows us to generate scratches. Smearing effects on the surface of an object create the illusion of 3D brush-strokes as if a painter had created brush strokes on a canvas. The rendering system is implemented using standard C and C++ programming languages. 3D models are then created using Alias MayaTM and TopmodTM

Illustrative interactive stipple rendering

Journal ArticleAbstract-Simulating hand-drawn illustration can succinctly express information in a manner that is communicative and informative. We present a framework for an interactive direct stipple rendering of volume and surface-based objects. By combining the principles of artistic and scientific illustration, we explore several feature enhancement techniques to create effective, interactive visualizations of scientific and medical data sets. We also introduce a rendering mechanism that generates appropriate point lists at all resolutions during an automatic preprocess and modifies rendering styles through different combinations of these feature enhancements. The new system is an effective way to interactively preview large, complex volume and surface data sets in a concise, meaningful, and illustrative manner. Stippling is effective for many applications and provides a quick and efficient method to investigate both volume and surface models

Structural focus+context rendering of multiclassified volume data

We present a F+C volume rendering system aimed at outlining structural relationships between different classification criteria of a multiclassified voxel model. We clusterize the voxel model into subsets of voxels sharing the same classification criteria and we construct an auxiliary voxel model storing for each voxel an identifier of its associated cluster. We represent the logical structure of the model as a directed graph having as nodes the classification criteria and as edges the inclusion relationships. We define a mapping function between nodes of the graph and clusters. The rendering process consists of two steps. First, given a user query defined in terms of a boolean expression of classification criteria, a parser computes a set of transfer functions on the cluster domain according to structural F+C rules. Then, we render simultaneously the original voxel model and the labelled one applying multimodal 3D texture mapping such that the fragment shader uses the computed transfer functions to apply structural F+C shading. The user interface of our system, based on Tulip, provides a visual feedback on the structure and the selection. We demonstrate the utility of our approach on several datasets.Postprint (published version

Attention and visual memory in visualization and computer graphics

Abstract—A fundamental goal of visualization is to produce images of data that support visual analysis, exploration, and discovery of novel insights. An important consideration during visualization design is the role of human visual perception. How we “see ” details in an image can directly impact a viewer’s efficiency and effectiveness. This paper surveys research on attention and visual perception, with a specific focus on results that have direct relevance to visualization and visual analytics. We discuss theories of low-level visual perception, then show how these findings form a foundation for more recent work on visual memory and visual attention. We conclude with a brief overview of how knowledge of visual attention and visual memory is being applied in visualization and graphics. We also discuss how challenges in visualization are motivating research in psychophysics

Stylized 3D Scene Synthesis in Virtual Reality

Many forms of life in the natural world have the extraordinary capacity to sense their environments, to learn, and to remember, just as humans do, even though they are vastly different from us. In this dissertation, I presented novel techniques developed to exhibit an interactive abstract virtual reality experience that invites viewers to see the natural world from a different perspective. I developed the vertex displacement and color turbulence approaches to showcase organisms. The organisms can also modulate their shapes according to the volumes and frequencies of sound. Furthermore, the experience displays turbulent flow on the organisms’ surface to demonstrate the concept of energy flow, or vitality, among all organisms in the natural world. Another novel feature is that viewers can interact with the surface colors through ray casting from a handheld controller