Evenly Spaced Streamlines for Surfaces: An Image-Based Approach

IEEE Transactions on Visualization and Computer Graphics, 2000

We introduce a novel flow visualization method called Flow Charts, which uses a texture atlas approach for the visualization of flows defined over curved surfaces. In this scheme, the surface and its associated flow are segmented into overlapping patches, which are then parameterized and packed in the texture domain. This scheme allows accurate particle advection across multiple charts in the texture domain, providing a flexible framework that supports various flow visualization techniques. The use of surface parameterization enables flow visualization techniques requiring the global view of the surface over long time spans, such as Unsteady Flow LIC (UFLIC), particle-based Unsteady Flow Advection Convolution (UFAC), or dye advection. It also prevents visual artifacts normally associated with view-dependent methods. Represented as textures, Flow Charts can be naturally integrated into hardware accelerated flow visualization techniques for interactive performance.

2016

Streamlines are commonly used for visualizing flow fields, but particle-tracing based streamline computation usually does not scale well as the data size and complexity increase. Large flow simulations like global ocean or climate models can obtain near perfect load balancing and the resulting data sets are generally analyzed in two dimensional slices. To match the computational properties of these simulations, we propose the use of flux-based stream functions for generating streamlines in parallel. In our method, local stream functions are efficiently generated per block based on flux conservation property, followed by low-cost communication of flux offsets among neighboring blocks. A scalar field is thus generated where streamlines can be extracted through parallel iso-contouring. Experimental results show that our system offers higher streamline computation performance with higher scalability than traditional particle-tracing based method.

Computer Graphics Forum, 2012

The ability to capture and visualize information within the flow poses challenges for visualizing 3D flow fields. Stream surfaces are one of many useful integration based techniques for visualizing 3D flow. However seeding integral surfaces can be challenging. Previous research generally focuses on manual placement of stream surfaces. Little attention has been given to the problem of automatic stream surface seeding. This paper introduces a novel automatic stream surface seeding strategy based on vector field clustering. It is important that the user can define and target particular characteristics of the flow. Our framework provides this ability. The user is able to specify different vector clustering parameters enabling a range of abstraction for the density and placement of seeding curves and their associated stream surfaces. We demonstrate the effectiveness of this automatic stream surface approach on a range of flow simulations and incorporate illustrative visualization techniques. Domain expert evaluation of the results provides valuable insight into the users requirements and effectiveness of our approach.

Computers & Graphics, 2001

The visualization of dense vector fields has important applications for scientific purposes. Beyond the standard methods, such as arrows and particle tracing, texture-based methods are able to show almost all the details of a field. This paper presents the Thick Oriented Stream-Line (TOSL) algorithm, which can show direction, orientation and local flow speed even for dense vector fields by simulating the convolution process. A practical comparison of the performances of TOSL vs. other visualizations algorithms (LIC and fastLIC) shows that the proposed algorithm can provide output textures faster than the other considered techniques. r

Proceedings Visualization '98 (Cat. No.98CB36276)

The success of using streamline technique for visualizing a vector field usually depends largely on the choice of adequate seed points. Turk and Banks developed an elegant technique for automatically placing seed points to achieve a uniform distribution of streamlines on a 2D vector field. Their method uses an energy function calculated from the low-pass filtered streamline image to guide the optimization process of the streamline distribution. This paper proposes a new technique for creating evenly distributed streamlines on 3D parametric surfaces found in curvilinear grids. We make use of Turk and Banks's 2D algorithm by first mapping the vectors on a 3D surface into the computational space of the curvilinear grid. To take into the consideration the mapping distortion caused by the uneven grid density in a curvilinear grid, a new energy function is designed and used for guiding the placement of streamlines in the computational space with desired local densities.

Advances in Engineering Software, 1989

The present streamline visualization program is based on the technique of mapping the physical domain to a rectangular block. The streamline computation proceeds by integrating the mapped velocity vectors in isoparametric cells and plotting the coordinates of the streamlines thus obtained. The mapping and interpolation use muitilinear functions, and the streamline equations are integrated by the classical Runge-Kutta method with a heuristic strategy for stepsize selection. An example integrating the streamlines in the solution of a vortical flowfieid over a delta wing at angle of attack demonstrates the use of the program.

Computational Geosciences, 2011

Streamline tracing on irregular grids requires reliable interpolation of velocity fields. We propose a new method for direct streamline tracing on polygon and polytope cells. While some numerical methods provide a basis function that can be used for interpolation, other methods provide only the fluxes at the faces of the elements. We introduce the concept of full field and raw field methods. Full field methods have built-in interpolation, but are often not defined on general grids such as polygonal and polyhedral grids which we examine here. Also, reliability issues may arise on non-simplicial meshes in terms of not being able to reproduce constant velocity fields. We propose an interpolation in H(div) and H(curl) valid on general grids that is based on barycentric coordinates and that reproduces uniform flow. The interpolation can be used to compute the streamline directly on the complex cell geometry. The method generalizes to convex polytopes in 3D, with a restriction on the polytope topology near corners that is shown to be satisfied by several popular grid types. Numerical results confirm that the method is applicable to general grids and preserves uniform flow.

Computers & Graphics, 2012

With increasing computing power, it is possible to process more complex fluid simulations. However, a gap between increasing data size and our ability to visualize them still remains. Despite the great amount of progress that has been made in the field of flow visualization over the last two decades, a number of challenges remain. Whilst the visualization of 2D flow has many good solutions, the visualization of 3D flow still poses many problems. Challenges such as domain coverage, speed of computation, and perception remain key directions for further research. Flow visualization with a focus on surface-based techniques forms the basis of this literature survey, including surface construction techniques and visualization methods applied to surfaces. We detail our investigation into these algorithms with discussions of their applicability and their relative strengths and drawbacks. We review the most important challenges when considering such visualizations. The result is an up-to-date overview of the current state-of-the-art that highlights both solved and unsolved problems in this rapidly evolving branch of research.

Proceedings of the 2009 Spring Conference on Computer Graphics - SCCG '09, 2009

This paper introduces Vector Field Perpendicular Surfaces as a means to represent vector data with special focus on variations across the vectors in the field. These surfaces are a perpendicular analogue to streamlines, with the vector data always being parallel to the normals of the surface. In this way the orientation of the data is conveyed to the viewer, while providing a continuous representation across the vectors of the field. This paper describes the properties of such surfaces including an issue with helicity density in the vector data, an approach to generating them, several stop conditions and special means to handle also fields with non-zero helicity density.

A new technique for interactive vector field visualization using large numbers of properly illuminated stream lines is presented. Taking into account ambient, diffuse, and specular reflection terms as well as transparency, we employ a realistic shading model which significantly increases quality and realism of the resulting images. While many graphics workstations offer hardware support for illuminating surface primitives, usually no means for an accurate shading of line primitives are provided. However, we show that proper illumination of lines can be implemented by exploiting the texture mapping capabilities of modern graphics hardware. In this way high rendering performance with interactive frame rates can be achieved. We apply the technique to render large numbers of integral curves in a vector field. The impression of the resulting images can be further improved by making the curves partially transparent. We also describe methods for controlling the distribution of stream lines in space. These methods enable us to use illuminated stream lines within an interactive visualization environment.