# Welcome To ParaView

- Copyright Notice
- Introduction
  - The Origins of ParaView
  - Features
- Compiling ParaView
- Execution

# Copyright Notice

Please see Copyright.txt or the online documentation here for the text of the copyright.

# Introduction

Welcome to ParaView, an application designed with the need to visualize large data sets in mind. The goals of the ParaView project include the following:

- Develop an open-source, multi-platform visualization application.
- Support distributed computation models to process large data sets.
- Create an open, flexible, and intuitive user interface.
- Develop an extensible architecture based on open standards.

ParaView runs on distributed and shared memory parallel as well as single processor systems and has been succesfully tested on Windows, Linux and various Unix workstations and clusters. Under the hood, ParaView uses the Visualization Toolkit as the data processing and rendering engine and has a user interface written using a unique blend of Tcl/Tk and C++.

The Origins of ParaView
ParaView is being developed by Kitware in conjunction with Jim Ahrens of the Advanced Computing Laboratory at Los Alamos National Laboratory. ParaView is funded by the US Department of Energy ASCI Views program as part of a three-year contract awarded to Kitware, Inc. by a consortium of three National Labs - Los Alamos, Sandia, and Livermore. The goal of the project is to develop scalable parallel processing tools with an emphasis on distributed memory implementations. The project includes parallel algorithms, infrastructure, I/O, support, and display devices. One significant feature of the contract is that all software developed is to be delivered open source. Hence ParaView is available as an open-source system.

Features
The following summarizes the important features of ParaView.

Visualization Capabilities:

Handles structured (uniform rectilinear, non-uniform rectilinear, and curvilinear grids), unstructured, polygonal and image data
All processing operations (filters) produce datasets. This allows the result of every operation to either be used for further processing or to be saved as a data file. For example, the user can extract a cut surface, reduce the number of points on this surface by masking, and apply glyphs (for example, vector arrows) to the result.
Contours and isosurfaces can be extracted from all data types using scalars or vector components. The results can be colored by any other variable or processed further. When possible, structured data contours/isosurfaces are extracted with fast and efficient algorithms which make use of the special data layout.
Vectors fields can be inspected by applying glyphs (currently arrows -vector arrows-, cones, lines, spheres, and various 2D glyphs) to the points in a dataset. The glyphs can be scaled by scalars, vector component or vector magnitude and can be oriented using a vector field.
A sub-region of a dataset can be extracted by cutting or clipping with an arbitrary plane (all data types), specifying a threshold criteria to exclude cells (all data types) and/or specifying a VOI (volume of interest - structured data types only)
Streamlines can be generated using constant step or adaptive integrators (currently, streamlines are not available in parallel; this feature is under development). The results can be displayed as points, lines, tubes, ribbons etc., and can be processed by a multitude of filters.
The points in a dataset can be warped (displaced) with scalars (given a user defined displacement vector) or with vectors (unavailable for rectilinear grids).
With the array calculator, new variables can be computed using existing point or cell field arrays. A multitude of scalar and vector operations are supported.
Data can be probed at a point or along a line. The results are displayed either graphically or as text and can be exported for further analysis.
ParaView provides many other data sources and filters by default (edge extraction, surface extraction, reflection, decimation, extrusion, smoothing...) and any VTK filter can be added by providing a simple XML description. (VTK provides hundreds of sources and filters, see VTK documentation for a complete list.)

Input/output and File Formats:

Supports a variety of file formats including: legacy VTK (all types including parallel, ascii and binary, can be read and written) VTK XML-based file formats (all types including parallel, ascii and binary, can be read and written) EnSight 6 and EnSight Gold (all types including parallel, ascii and binary; multiple parts are supported -each part is loaded separately and can be processed individually) (read only) Plot3D (ascii and binary, C or Fortran; support for multiple blocks -each block is loaded separately and can be processed individually-, I blanking is currently partially supported) (read only) Various polygonal file formats including STL and BYU (by default, read only, other VTK writers can be added by writing XML description)
Since ParaView is open source, the user can easily provide her own readers and writers.

User Interaction:

Intuitive and flexible interface based on the Tcl/Tk toolkit.
Compact user interface design. All tools are located in the main window. This eliminates the need for large number of windows which are often difficult to locate on a cluttered desktop.
Allows changing the parameters of many filters by directly interacting with the 3D view using 3D widgets (manipulators). For example, the user can manipulate the seed line of a streamtrace filter by clicking on a control point and dragging the line to the new location.
Maintains interactive frame rates even when working with large data through the use of level-of-detail (LOD) models. The user determines the threshold (number of points) beyond which a reduced version of the model is displayed during interaction. (The size of the model can also be adjusted.) Once the interaction is over, the large model is rendered.

Large Data and Distributed computing:

Runs in parallel on distributed and shared memory systems using MPI. These include workstation clusters, visualization systems, large servers, supercomputers, etc.
ParaView uses the data parallel model in which the data is broken into pieces to be processed by different processes. Most of the visualization algorithms function without any change when running in parallel. ParaView also supports ghost levels used to produce piece invariant results. Ghost levels are points/cells shared between processes and are used by algorithms which require neighborhood information.
Supports both distributed rendering (where the results are rendered on each node and composited later using the depth buffer), local rendering (where the resulting polygons are collected on one node and rendered locally) and a combination of both. (For example, the level-of-detail models can be rendered locally whereas the full model is rendered in a distributed manner.) This provides scalable rendering for large data without sacrificing performance when working with smaller data.

Scripting and extensibility:

ParaView is fully scriptable using the simple but powerful Tcl language. Every operation has a corresponding script command. Every command executed during a session can be saved in a trace file which can be re-loaded to reproduce the session. Furthermore, since the session file is simply a Tcl script, it can be edited/modified and loaded to obtain different results.
Additional modules can be added by either writing an XML description of the interface (Since the XML interface is still being developed, it is not fully documented and is subject to change.) or by writing special C++ sub-classes of the main ParaView module (This is only needed for advanced modules.). The XML interface allows users/developers to add their own VTK filters to ParaView without writing any special code and/or re-compiling. (ParaView can load shared Tcl wrapper libraries at run time.)
Since the user interface is written with Tk, it can be modified and extended at runtime either from the command prompt or by loading a ParaView script. For example, it is possible to write a demonstation script which brings up a message window describing the current operation as well as allowing the user to interrupt the demo.

# Compiling ParaView

Please see Compiling.html or the online documentation here for instructions.

# Execution

For information about how to start and use ParaView, see the online documentation.