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Introduction

 
What is Finite Element Method?
Finite element Method is a widely used numerical technique for finding solutions of partial differential equations. FEM is based on discretizing a domain into elements (and nodes) and constructing basis (or interpolation) functions across the elements. Applications of finite element method include linear and nonlinear structural, thermal, dynamic, electromagnetic, and flow analysis.

The toolkits of FEM Visualization
Visualization of FEM  is of great importance because of its principle idea and the information people want to directly perceived from the result data. There are lots of visualiztion packages contributed to FEM visualization, some of the widely used toolkits are:

What is VTK?

The Visualization ToolKit (vtk) is a software system for 3D computer graphics, image and volume processing, and visualization. VTK includes a C++ class library, and several interpreted interface layers including Tcl/Tk, Java, and Python. VTK has been implemented on nearly every Unix-based platform and PC's (Windows NT and Windows95). The design and implementation of the library has been strongly influenced by object-oriented principles.

The graphics model in VTK is at a higher level of abstraction than rendering libraries like OpenGL or PEX. This means it is much easier to create useful graphics and visualization applications. In VTK, applications can be written directly in C++, Tcl, Java, or Python. In fact, using the interpreted languages Tcl or Python with Tk, and even Java with its GUI class libraries, it is possible to build useful applications really, really fast.

Finally, the software is a true visualization system, it doesn't just let you visualize geometry. VTK supports a wide variety of visualization algorithms including scalar, vector, and tensor visualization, and advanced modelling techniques like implicit modelling, polygon reduction, and Delaunay triangulation.Moreover, it is free! There is a  An introduction to VTK by Rechard Resnick in the advanced topics of CS563'97 and more on  http://www.kitware.com/vtk.html .

Visualization Tool Kit Architecture

VTK uses visualization pipeline or visualization network to construct an application. A comprehensive overview of these process is available. A simplified visualization pipeline is shown in Figure 1. It consists of Source, Filter, Mapper, and Display processes. The functions of these processes are: