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Review of Visualisation Systems

5.1 Application Visualization System (AVS)

5.1.1 - Hardcopy facilities
5.1.2 - Files
5.1.3 - Animation and Video facilities

5.1.1 Hardcopy facilities

There are two main methods within AVS to generate postscript files (monochrome and colour) from scenes and images in the Geometry Viewer and Image Viewer modules are:

Image to Postscript Module

This module takes as its input a standard AVS image and converts the output to Postscript in a file on the system. The module supports two types of postscript output:

The module also allows the user to specify: orientation: landscape or portrait style: encapsulated (for inclusion into other packages) size: the page x and y size in inches

One of the problems with this module though is that it generates images at a resolution of the screen (100 dpi) whereas most printers have a higher (300 dpi) resolution. One method of increasing the resolution the module can produce is to enlarge the image using the geometry_viewer facilities.

geom_save_postscript CLI command

This is the preferred method of generating output from the geometry_viewer module. This CLI command will output the contents of the geometry_viewer window using Postscript lines and text where possible to improve the quality of output. There is however no conversion of polygons to the appropriate postscript representations. To use the facility you must run AVS with the command line interpreter running and when you are happy with the scene in the geometry_viewer execute the CLI command.

5.1.2 Files

There are a number of modules which produce output files from various stages in an AVS network. These are listed below with a brief description:

Standard AVS modules

Image to CGM: converts the input image into the Computer Graphics Metafile (CGM) format. All three encodings, binary, character and clear text are supported and control is provided for the page height and width and orientation.

Write field: writes an AVS field data type to disk. The file has two sections: an ASCII header and the data written in a binary format. The module allows control on the format of the binary portion and it can be written in the machine's native format or in Sun's (external data representation) XDR format which is useful for transporting files across machine ranges.

Write UCD: writes unstructured cell data to a file in either binary (compact) or ASCII (human readable) format.

Write image: writes an AVS image data structure to a file. These files can be read by the AVS module read_image and some public domain image conversion software e.g., customised versions of xv and it is a supported format for the San Diego Image Toolkit.

Write volume: writes an AVS volume data structure to disk. These files can be read by the AVS module read_volume.

ip write vff: converts an AVS image data structure into a SunVision binary vff image format file.

Write structure file: convert an AVS Molecule Data Type (MDT) data structure into a structure file (and associated formal charge file). A structure file is one of the formats supported within the AVS Chemistry Developers Kit.

Public domain modules

Create_MPEG: creates MPEG movies from a series of AVS images. It makes use of Andy Hung's MPEG which is available by anonymous ftp from Stanford. Geom_to_Wavefront: generates an equivalent Wavefront (.obj) file for each polyhedron and polytriangle in an AVS Geometry object.

WRITE_ANY_IMAGE: This module writes an image from an AVS Network in a variety of formats which the San Diego Supercomputing Center's image tools support. Any of the following image file formats can be written by this module:

field2_to_Math: allows a two-dimensional scalar field to be imported into Mathematica from AVS. The session is initialised with a package of Mathematica commands which start a MathLink communication channel to AVS. Other initialisations are made so that the Mathematica command AVSReadField will read a two-dimensional scalar field from AVS.

field_to_EXCEL: ASCII Excel spreadsheet format files are produces containing field data in a table format. These files can be imported into a suitable excel format for analysis and plotting. Separator characters may be specified for differing output versions, three possible floating point output formats are selectable, and the maximum number of values per line is adjustable.

Output a60: The output a60 module takes an AVS image data structure as input, converts it into Abekas YUV format and sends it to an Abekas a60 digital disk recorder.

ucd_to_wave: The ucd to wave module writes a ucd structure to disk, in wavefront format, which is supported by Data Visualizer. Ucd to wave works only with node data, therefore if you have cell data, you have to transform the cell data to node data using the cell to node module.

write_Dore_i: converts an AVS image data structure into Dore format

write_KSWAD: converts an AVS image data structure into a KSWAD format

write_MooV: Create QuickTime sequences from AVS images. This code currently requires, the QuickTime Movie Exchange Toolkit, which is available from Apple, Inc, and a C++ compiler (you also need the C++ compiler to build the QuickTime libraries.

write_jpeg: Compresses an image with the JPEG compression standard and writes it to a file.

5.1.3 Animation and Video facilities

Standard AVS

With standard AVS users can control the behaviour of downstream modules in an AVS network by using the animated float and animated integer modules. These modules both output a stream of numbers which can be used to control the parameters of modules downstream in the network. The modules allow the user to input the minimum and maximum range of the numbers along with the number of intervals or steps to proceed with. This allows the control and generation of flipbook style of animation.

The modules image_viewer and geometry viewer both have facilities for the creation of simple flipbook animation by recording a sequence of images or geometries and then playing them back from memory. The playback speed and performance is highly dependent on the platforms rendering speed and memory configuration.

Public domain modules

There are a few public domain modules which provide animation facilities extra to the ones in standard AVS. The create_mpeg module has been mentioned in the previous section on file output.

CICA Keyframe module: this module is connected to the geometry viewer module and controls the of objects by manipulating their transformation matrixes. The user can define a number of keyframes and then interpolate between them using linear or spline interpolation.

Fast Animate: this module is designed animate a series of AVS geometries which have been written to disk. The files are defined with a prefix and then a frame sequencing number with controls to step forward, back and play a sequence.

AVS Animator

The AVS animator package consists of a number of modules and a separate license to the standard AVS one is needed to use the AVS animator module.

The package consists:

AVS Animator is the main module within the package and provides a front end to the keyframe style of animation. The animator module can control the rendering modules: image viewer, geometry viewer, graph viewer etc. It can also control the parameters associated with modules in the same AVS network upstream of these rendering modules.

The user generates an animated sequence or script by defining a number of keyframes and then asking the AVS Animator to in-between or interpolate between these keyframes. The keyframe definition consists of the objects attribute information within the rendering module and also the parameter settings in the modules upstream of the renderer. An example scenario could be a rotating dataset with the isosurface value changing from its minimum to maximum value. Obviously more complex animations are possible.

When an animation has been generated the user has to hand a more complex user interface to control the aspects affected at each keyframe (see figure 10). This allows the user to edit the final sequence.

As the animator module generates an animated sequence useful information is sent out of its output ports: frames/second, frame number and current time.

Finally the animator allows the user to save and load scripts that they have generated.

Along with the main animator module come a number of support modules:

Write Frame Sequence: compress a series of images which make up a flipbook style of animation into a single file. The module can also add and delete frames from an existing frame sequence file. It is useful for collecting images from a simulation where each time step takes a time to calculate.

Read Frame Sequence: read a series of files written to a frame sequence file by the write frame sequence module. The module has the animator style control panel and optional controls over the playback speed and current frame.

Prepare video: pre-process animations before sending them to a video device. The processing that is supported:

Output ImageNode and Output VideoCreator: two example modules for the DiaQuest Inc. and Silicon Graphics VideoCreator video boards. These modules serve as examples for users who wish to interface to other video output hardware.

Review of Visualisation Systems
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