Results 1 - 10
of
157
Exaggerated Shading for Depicting Shape and Detail
- PROC. OF ACM SIGGRAPH, ACM TRANS. ON GRAPHICS
, 2006
"... In fields ranging from technical illustration to mapmaking, artists have developed distinctive visual styles designed to convey both detail and overall shape as clearly as possible. We investigate a non-photorealistic shading model, inspired by techniques for cartographic terrain relief, based on dy ..."
Abstract
-
Cited by 67 (5 self)
- Add to MetaCart
In fields ranging from technical illustration to mapmaking, artists have developed distinctive visual styles designed to convey both detail and overall shape as clearly as possible. We investigate a non-photorealistic shading model, inspired by techniques for cartographic terrain relief, based on dynamically adjusting the effective light position for different areas of the surface. It reveals detail regardless of surface orientation and, by operating at multiple scales, is designed to convey detail at all frequencies simultaneously.
Size-based Transfer Functions: A New Volume Exploration Technique
- IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS
, 2008
"... The visualization of complex 3D images remains a challenge, a fact that is magnified by the difficulty to classify or segment volume data. In this paper, we introduce size-based transfer functions, which map the local scale of features to color and opacity. Features in a data set with similar or i ..."
Abstract
-
Cited by 50 (4 self)
- Add to MetaCart
(Show Context)
The visualization of complex 3D images remains a challenge, a fact that is magnified by the difficulty to classify or segment volume data. In this paper, we introduce size-based transfer functions, which map the local scale of features to color and opacity. Features in a data set with similar or identical scalar values can be classified based on their relative size. We achieve this with the use of scale fields, which are 3D fields that represent the relative size of the local feature at each voxel. We present a mechanism for obtaining these scale fields at interactive rates, through a continuous scale-space analysis and a set of detection filters. Through a number of examples, we show that size-based transfer functions can improve classification and enhance volume rendering techniques, such as maximum intensity projection. The ability to classify objects based on local size at interactive rates proves to be a powerful method for complex data exploration.
A Nested Model for Visualization Design and Validation
"... Abstract—We present a nested model for the visualization design and validation with four layers: characterize the task and data in the vocabulary of the problem domain, abstract into operations and data types, design visual encoding and interaction techniques, and create algorithms to execute techni ..."
Abstract
-
Cited by 46 (5 self)
- Add to MetaCart
(Show Context)
Abstract—We present a nested model for the visualization design and validation with four layers: characterize the task and data in the vocabulary of the problem domain, abstract into operations and data types, design visual encoding and interaction techniques, and create algorithms to execute techniques efficiently. The output from a level above is input to the level below, bringing attention to the design challenge that an upstream error inevitably cascades to all downstream levels. This model provides prescriptive guidance for determining appropriate evaluation approaches by identifying threats to validity unique to each level. We also provide three recommendations motivated by this model: authors should distinguish between these levels when claiming contributions at more than one of them, authors should explicitly state upstream assumptions at levels above the focus of a paper, and visualization venues should accept more papers on domain characterization. Index Terms—Models, frameworks, design, evaluation.
Illustrative context-preserving exploration of volume data
- IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS
, 2006
"... In volume rendering, it is very difficult to simultaneously visualize interior and exterior structures while preserving clear shape cues. Highly transparent transfer functions produce cluttered images with many overlapping structures, while clipping techniques completely remove possibly important co ..."
Abstract
-
Cited by 44 (10 self)
- Add to MetaCart
(Show Context)
In volume rendering, it is very difficult to simultaneously visualize interior and exterior structures while preserving clear shape cues. Highly transparent transfer functions produce cluttered images with many overlapping structures, while clipping techniques completely remove possibly important context information. In this paper, we present a new model for volume rendering, inspired by techniques from illustration. It provides a means of interactively inspecting the interior of a volumetric data set in a featuredriven way which retains context information. The context-preserving volume rendering model uses a function of shading intensity, gradient magnitude, distance to the eye point, and previously accumulated opacity to selectively reduce the opacity in less important data regions. It is controlled by two user-specified parameters. This new method represents an alternative to conventional clipping techniques, sharing their easy and intuitive user control, but does not suffer from the drawback of missing context information.
Gaussian transfer functions for multi-field volume visualization
- In IEEE Visualization
, 2003
"... Volume rendering is a flexible technique for visualizing dense 3D volumetric datasets. A central element of volume rendering is the conversion between data values and observable quantities such as color and opacity. This process is usually realized through the use of transfer functions that are prec ..."
Abstract
-
Cited by 43 (6 self)
- Add to MetaCart
Volume rendering is a flexible technique for visualizing dense 3D volumetric datasets. A central element of volume rendering is the conversion between data values and observable quantities such as color and opacity. This process is usually realized through the use of transfer functions that are precomputed and stored in lookup tables. For multidimensional transfer functions applied to multivariate data, these lookup tables become prohibitively large. We propose the direct evaluation of a particular type of transfer functions based on a sum of Gaussians. Because of their simple form (in terms of number of parameters), these functions and their analytic integrals along line segments can be evaluated efficiently on current graphics hardware, obviating the need for precomputed lookup tables. We have adopted these transfer functions because they are well suited for classification based on a unique combination of multiple data values that localize features in the transfer function domain. We apply this technique to the visualization of several multivariate datasets (CT, cryosection) that are difficult to classify and render accurately at interactive rates using traditional approaches.
Lighting transfer functions using gradient aligned sampling
- In IEEE Visualization
, 2004
"... ABSTRACT An important task in volume rendering is the visualization of boundaries between materials. This is typically accomplished using transfer functions that increase opacity based on a voxel's value and gradient. Lighting also plays a crucial role in illustrating surfaces. In this paper w ..."
Abstract
-
Cited by 41 (5 self)
- Add to MetaCart
(Show Context)
ABSTRACT An important task in volume rendering is the visualization of boundaries between materials. This is typically accomplished using transfer functions that increase opacity based on a voxel's value and gradient. Lighting also plays a crucial role in illustrating surfaces. In this paper we present a multi-dimensional transfer function method for enhancing surfaces, not through the variation of opacity, but through the modification of surface shading. The technique uses a lighting transfer function that takes into account the distribution of values along a material boundary and features a novel interface for visualizing and specifying these transfer functions. With our method, the user is given a means of visualizing boundaries without modifying opacity, allowing opacity to be used for illustrating the thickness of homogeneous materials through the absorption of light.
Line drawings from volume data
- ACM Trans. Graph
, 2005
"... classroom use is granted without fee provided that copies are not made or distributed for commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitt ..."
Abstract
-
Cited by 41 (2 self)
- Add to MetaCart
classroom use is granted without fee provided that copies are not made or distributed for commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Permissions
Robust Particle Systems for Curvature Dependent Sampling of Implicit Surfaces
- In SMI ’05: Proceedings of the International Conference on Shape Modeling and Applications 2005 (SMI’ 05
, 2005
"... Recent research on point-based surface representations suggests that point sets may be a viable alternative to parametric surface representations in applications where the topological constraints of a parameterization are unwieldy or inefficient. Particle systems offer a mechanism for controlling po ..."
Abstract
-
Cited by 40 (5 self)
- Add to MetaCart
(Show Context)
Recent research on point-based surface representations suggests that point sets may be a viable alternative to parametric surface representations in applications where the topological constraints of a parameterization are unwieldy or inefficient. Particle systems offer a mechanism for controlling point samples and distributing them according to needs of the application.Furthermore, particle systems can serve as a surface representation in their own right, or to augment implicit functions, allowing for both efficient rendering and control of implicit function parameters. The state of the art in surface sampling particle systems, however, presents some shortcomings. First, most of these systems have many parameters that interact with some complexity, making it difficult for users to tune the system to meet specific requirements. Furthermore, these systems do not lend themselves to spatially adaptive sampling schemes, which are essential for efficient, accurate representations of complex surfaces. In this paper we present a new class of energy functions for distributing particles on implicit surfaces and a corresponding set of numerical techniques. These techniques provide stable, scalable, efficient, and controllable mechanisms for distributing particles that sample implicit surfaces within a locally adaptive framework. 1.
Enhancing depth-perception with flexible volumetric halos
- IEEE Transactions on Visualization and Computer Graphics
"... Abstract—Volumetric data commonly has high depth complexity which makes it difficult to judge spatial relationships accurately. There are many different ways to enhance depth perception, such as shading, contours, and shadows. Artists and illustrators frequently employ halos for this purpose. In thi ..."
Abstract
-
Cited by 40 (5 self)
- Add to MetaCart
(Show Context)
Abstract—Volumetric data commonly has high depth complexity which makes it difficult to judge spatial relationships accurately. There are many different ways to enhance depth perception, such as shading, contours, and shadows. Artists and illustrators frequently employ halos for this purpose. In this technique, regions surrounding the edges of certain structures are darkened or brightened which makes it easier to judge occlusion. Based on this concept, we present a flexible method for enhancing and highlighting structures of interest using GPU-based direct volume rendering. Our approach uses an interactively defined halo transfer function to classify structures of interest based on data value, direction, and position. A feature-preserving spreading algorithm is applied to distribute seed values to neighboring locations, generating a controllably smooth field of halo intensities. These halo intensities are then mapped to colors and opacities using a halo profile function. Our method can be used to annotate features at interactive frame rates. Index Terms—Volume rendering, illustrative visualization, halos. 1
Visualization of boundaries in volumetric data sets using LH histograms
- IEEE Trans. Vis. Comput. Graph
"... ..."
(Show Context)
