Transfer Function Design Research Articles

Contrast Transfer Function Design by an Electrostatic Phase Plate

Extract Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007

A software tool for interactive generation, representation, and systematical storage of transfer functions for 3D medical images

As being a tool that assigns optical parameters, i.e. color, transparency, used in interactive visualization, transfer functions have very important effects on the quality of volume rendered medical images. However, finding accurate transfer functions is a very difficult, tedious, and time consuming task because of the variety of all possibilities. By addressing this problem, a software module, which can be easily plugged into any visualization program, is developed based on the specific expectations of medical experts. Its design includes both a new user interface to ease the interactive generation of the volume rendered medical images and a volumetric histogram based method for initial generation of transfer functions. In addition, a novel file system has been implemented to represent 3D medical images using transfer functions based on the DICOM standard. For evaluation of the system by various medical experts, the software is installed into a DICOM viewer. Based on the feedback obtained from the medical experts, several improvements are made, especially to increase the flexibility of the program. The final version of the implemented system shortens the transfer function design process and is applicable to various application areas.

Opacity Peeling for Direct Volume Rendering

Abstract The most important technique to visualize 3D scalar data, as they arise e.g. in medicine from tomographic measurement, is direct volume rendering. A transfer function maps the scalar values to optical properties which are used to solve the integral of light transport in participating media. Many medical data sets, especially MRI data, however, are difficult to visualize due to different tissue types being represented by the same scalar value. The main problem is that interesting structures will be occluded by less important structures because they share the same range of data values. Occlusion, however, is a view‐dependent problem and cannot be solved easily by transfer function design. This paper proposes a new method to display different entities inside the volume data in a single rendering pass. The proposed opacity peeling technique reveals structures in the data set that cannot be visualized directly by one‐or multi‐dimensional transfer functions without explicit segmentation. We also demonstrate real‐time implementations using texture mapping and multiple render targets. Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three‐Dimensional Graphics and Realism

High-Level User Interfaces for Transfer Function Design with Semantics

Many sophisticated techniques for the visualization of volumetric data such as medical data have been published. While existing techniques are mature from a technical point of view, managing the complexity of visual parameters is still difficult for non-expert users. To this end, this paper presents new ideas to facilitate the specification of optical properties for direct volume rendering. We introduce an additional level of abstraction for parametric models of transfer functions. The proposed framework allows visualization experts to design high-level transfer function models which can intuitively be used by non-expert users. The results are user interfaces which provide semantic information for specialized visualization problems. The proposed method is based on principal component analysis as well as on concepts borrowed from computer animation.

Visualization of boundaries in volumetric data sets using LH histograms

A crucial step in volume rendering is the design of transfer functions that will highlight those aspects of the volume data that are of interest to the user. For many applications, boundaries carry most of the relevant information. Reliable detection of boundaries is often hampered by limitations of the imaging process, such as blurring and noise. We present a method to identify the materials that form the boundaries. These materials are then used in a new domain that facilitates interactive and semiautomatic design of appropriate transfer functions. We also show how the obtained boundary information can be used in region-growing-based segmentation.

Local Histograms for Design of Transfer Functions in Direct Volume Rendering

Direct Volume Rendering (DVR) is of increasing diagnostic value in the analysis of data sets captured using the latest medical imaging modalities. The deployment of DVR in everyday clinical work, however, has so far been limited. One contributing factor is that current Transfer Function (TF) models can encode only a small fraction of the user's domain knowledge. In this paper, we use histograms of local neighborhoods to capture tissue characteristics. This allows domain knowledge on spatial relations in the data set to be integrated into the TF. As a first example, we introduce Partial Range Histograms in an automatic tissue detection scheme and present its effectiveness in a clinical evaluation. We then use local histogram analysis to perform a classification where the tissue-type certainty is treated as a second TF dimension. The result is an enhanced rendering where tissues with overlapping intensity ranges can be discerned without requiring the user to explicitly define a complex, multidimensional TF.

A209 レーザー核融合における爆縮現象の位相解析と可視化

This paper presents the design of multi-dimensional transfer functions which take into account the nested structures of evolving isosurfaces in a given volume dataset. The effectiveness of the resultant topological transfer functions is proven empirically through an application to a simulated dataset for implosion phenomena in laser fusion.

Robust model following control of parallel buck converters

A robust model-following (RMF) control technique for average current mode controlled (ACC) parallel buck dc-dc converters, RMFACC, is presented. RMFACC achieves that the loop gain of the voltage loop is little sensitive to the variation of power stage parameters: number of modules, input voltage, load, and component tolerances. The design of the voltage loop is 'decoupled' from the design of the disturbance rejection transfer functions in an important degree, so that the output impedance and audio susceptibility are greatly reduced without the need of high loop gain crossover frequencies. A comparative study between conventional ACC and RMFACC is shown.

Design of Multi-Dimensional Transfer Functions with Topological Attributes

Design of Multi-Dimensional Transfer Functions with Topological Attributes

Topological volume skeletonization and its application to transfer function design

Topological volume skeletonization is a novel approach for automating transfer function design in visualization by extracting the topological structure of a volume dataset. The skeletonization process yields a graph called a volume skeleton tree, which consists of volumetric critical points and their connectivity. The resultant graph provides critical field values whose color and opacity are accentuated in the design of transfer functions for direct volume rendering. Visually pleasing results of volume visualization demonstrate the feasibility of the present approach.

Filter design: a finite dimensional convex optimization approach

AbstractWe consider the design of transfer functions (filters) satisfying upper and lower bounds on the frequency response magnitude or on phase response, in the continuous and discrete time domains. The paper contribution is to prove that such problems are equivalent tofinitedimensionalconvexoptimization problems involving linear matrix inequality constraints. At now, such optimization problems can be efficiently solved. Note that this filter design problem is usually reduced to a semi infinite dimensional linear programming optimization problem under the additional assumption that the filter poles are fixed (for instance, when considering FIR design). Furthermore, the semi infinite dimensional optimization is practically solved, using a gridding approach on the frequency. In addition to be finite dimensional, our formulation allows to set or not the filter poles. These problems were mainly considered in signal processing. Our interest is to propose an approach dedicated to automatic control problems. In this paper, we focus on the following problems: design of weighting transfers forH∞control and design of lead‐lag networks for control. Numerical applications emphasize the interest of the proposed results. Copyright © 2003 John Wiley & Sons, Ltd.

3DIVE: An immersive environment for interactive volume data exploration

This paper describes an immersive system, called 3DIVE, for interactive volume data visualization and exploration inside the CAVE virtual environment. Combining interactive volume rendering and virtual reality provides a natural immersive environment for volumetric data visualization. More advanced data exploration operations, such as object level data manipulation, simulation and analysis, are supported in 3DIVE by several new techniques. In particular, volume primitives and texture regions are used for the rendering, manipulation, and collision detection of volumetric objects; and the region-based rendering pipeline is integrated with 3D image filters to provide an image-based mechanism for interactive transfer function design. The system has been recently released as public domain software for CAVE/ImmersaDesk users, and is currently being actively used by various scientific and biomedical visualization projects.

ボリュームデータマイニングのための伝達関数の合成

Analytic, simulated, scanned datasets were used to evaluate two representative data-centric methods for designing transfer functions (TFs), which are a key factor determining the quality of volume rendered images. They map the physical fields of a given volume dataset to the optical properties, such as color and opacity. Designing proper TFs is difficult because they depend on both the context of the target volume dataset and the purpose of the visual exploration. A system called “Ivory” was developed to assist in the design of TFs. With it, a better TF can be composed so as to inherit different features from two original TFs.

Algebraic solution to the robust SPR problem for two polynomials

In this paper we provide an algebraic method for the design of an appropriate transfer function making simultaneously two polynomials strictly positive real (SPR), in the so-called robust SPR problem for two polynomials. This problem arises in the design of recursive estimation algorithms used for identification purposes and in active noise control (ANC) applications. In the former a given transfer function involving the poles of the unknown transfer function must be made SPR; in the latter, the phase of a transfer function must be matched within a range of (− π /2, π /2) . Robust SPR design methods try to fulfill the phase requirements for all possible transfer functions belonging to a given uncertainty description. Here we focus on uncertainties described by two polynomials.

Methods for the transfer function design of multiple narrow-band bandpass sigma–delta modulators

This paper presents the design analysis of novel tunable narrow-band bandpass sigma–delta modulators, which can achieve concurrent multiple noise-shaping for multi-tone input signals. Four different design methodologies based on the noise transfer functions of comb filters, slink filters, multi-notch filters and fractional delay comb filters are applied for the design of these multiple-band sigma–delta modulators. The latter approach utilises conventional comb filters in conjunction with FIR, or allpass IIR fractional delay filters, to deliver the desired nulls for the quantisation noise transfer function. Detailed simulation results show that FIR fractional delay comb filter-based sigma–delta modulators tune accurately to most centre frequencies, but suffer from degraded resolution at frequencies close to Nyquist. However, superior accuracies are obtained from their allpass IIR fractional delay counterpart at the expense of a slight shift in noise-shaping bands at very high frequencies. The merits and drawbacks of each technique for the various sigma–delta topologies are assessed in terms of in-band signal-to-noise ratios, accuracy of tunability and coefficient complexity for ease of implementation.

Algebraic solution to the robust SPR problem for two polynomials

In this paper we provide an algebraic method for the design of an appropriate transfer function making simultaneously two polynomials strictly positive real (SPR), in the so-called robust SPR problem for two polynomials. This problem arises in the design of recursive estimation algorithms used for identification purposes and in active noise control (ANC) applications. In the former a given transfer function involving the poles of the unknown transfer function must be made SPR; in the latter, the phase of a transfer function must be matched within a range of (− π/2, π/2) . Robust SPR design methods try to fulfill the phase requirements for all possible transfer functions belonging to a given uncertainty description. Here we focus on uncertainties described by two polynomials.

Volume illustration: nonphotorealistic rendering of volume models

Accurately and automatically conveying the structure of a volume model is a problem which has not been fully solved by existing volume rendering approaches. Physics-based volume rendering approaches create images which may match the appearance of translucent materials in nature but may not embody important structural details. Transfer function approaches allow flexible design of the volume appearance but generally require substantial hand-tuning for each new data set in order to be effective. We introduce the volume illustration approach, combining the familiarity of a physics-based illumination model with the ability to enhance important features using non-photorealistic rendering techniques. Since the features to be enhanced are defined on the basis of local volume characteristics rather than volume sample values, the application of volume illustration techniques requires less manual tuning than the design of a good transfer function. Volume illustration provides a flexible unified framework for enhancing the structural perception of volume models through the amplification of features and the addition of illumination effects.

The transfer function bake-off

Direct volume rendering is a key technology for visualizing large 3D data sets from scientific or medical applications. Transfer functions are particularly important to the quality of direct volume-rendered images. A transfer function assigns optical properties, such as color and opacity, to original values of the data set being visualized. Unfortunately, finding good transfer functions proves difficult. It is one of the major problems in volume visualization. The article examines four of the currently most promising approaches to transfer function design. The four approaches are: trial and error, with minimum computer aid; data-centric, with no underlying assumed model; data-centric, using an underlying data model; and image-centric, using organized sampling.

3Dive: An Immersive Environment for Interactive Volume Data Exploration

This paper describes an immersive system, called 3DIVE, for interactive volume data visualization and exploration inside the CAVE virtual environment. Combining interactive volume rendering and virtual reality provides a natural immersive environment for volumetric data visualization. More advanced data exploration operations, such as object level data manipulation, simulation and analysis, are supported in 3DIVE by several new techniques: volume primitives and texture regions are used for the rendering, manipulation, and collision detection of volumetric objects; the region based rendering pipeline is integrated with 3D image filters to provide an image-based mechanism for interactive transfer function design; a collaborative visualization module allows remote sites to collaborate over common datasets with passive or active view sharing. The system has been recently released as public domain software for CAVE/ImmersaDesk users, and is currently being actively used by a 3D microscopy visualization project.

Three-dimensional microscopy data exploration by interactive volume visualization.

This paper presents a new volume visualization approach for three-dimensional (3-D) interactive microscopy data exploration. Because of their unique image characteristics, 3-D microscopy data are often not able to be visualized effectively by conventional volume visualization techniques. In our approach, microscopy visualization is carried out in an interactive data exploration environment, based on a combination of interactive volume rendering techniques and image-based transfer function design methods. Interactive volume rendering is achieved by using two-dimensional (2-D) texture mapping in a Shear-Warp volume rendering algorithm. Image processing techniques are employed and integrated into the rendering pipeline for the definition and searching of appropriate transfer functions that best reflect the user's visualization intentions. These techniques have been implemented successfully in a prototype visualization system on low-end and middle-range SGI desktop workstations. Since only 2-D texture mapping is required, the system can also be easily ported to PC platforms.