How does the Shaper compact file format work exactly?
The professional version of the iChrome’s CAE Viewer and Shaper provide a way to import results from third party FE solvers (such as Nastran OP2 file, Abaqus ODB files, Ansys RES files) and save (i.e. export) them in a so-called compact format. In this post we will explain and provide few additional details and information on how the compact format works and how to better exploit its capabilities and options.
Before getting our feet wet with file format details and options, a gentle introduction to the fundamentals of Shaper Compact files:
- compact files use a proprietary binary format designed by iChrome to save FE models and relevant results. It has been designed to generate portable and cross-platform files;
- compact files can be used to share and visualize models and related results within the iChrome’s CAE Viewer and Shaper. As a free version of the CAE Viewer is available for download, exporting models in Shaper compact format allows sharing results potentially with any third party;
- in order to save disk space, the compact format allows:
- saving only sub-set of the information originally part of the FE model. Users can thus opt to save a subset of the original results;
- saving data such as nodal positions and FE results either on single or double precision format;
- saving only visible elements, which means saving only free faces of solid elements. At one end, this drastically reduces the size of results to be saved on file but on the other prevents sectioning solid models and visualize internal parts;
- reducing the order of the elements to their corresponding first order formulation. Note this option has effect only if used along with the Compact Format one
Before We Start:
In order to export models from within the Graphical Interface of Shaper (or equivalently the CAE Viewer):
Once a FE model and relevant results are loaded in memory, from the main toolbar click on button Export Assembly.
The Compact Exporter Wizard allow you to select the destination file where results should be save to. There are three main options:
- Compact Format:by selecting this flag, the exporter saves only visible elements (i.e. free faces) and relevant results.
- Single Precision:by selecting this flag, the exporter saves nodal positions and results in single precision format.
- Reduced Order: by selecting this flag, the exporter reduces second order elements to their corresponding first order ones. This reduces the overall number of nodes used to describe the model and compacts results accordingly. By selecting this option however not all nodes will be available on saved model.
- Results: users can select which table of results (among the available ones) should be included in the file.
This section considers 3 FE models and analyses the disk space required to save them in the Shaper compact format with different options.
To be fair, when comparing the original third party files with the compact Shaper ones, please consider that the shaper compact files contain only a sub-set of the data stores in the original third party files. Provided comparisons however can be useful to assess the different options made available and how these affect the file dimensions.
Model 1: Nastran Solid Model
Description:Solid assembly. Second order tetra elements
Nodes: 410 k
Elements: 260 k
Load cases: 5
Original set of results: element stress, displacements, SPC and MPC forces
Compact file set of results: element stress, displacement, 3 load cases only
OP2 Size: 777 Mb
SHP (1): 226.3 Mb
SHP (2): 131.5 Mb
SHP (3): 57.2 Mb
SHP (4): 38.1 Mb
SHP (5): 21.3 Mb
Model 2: Nastran Shell Model
Description: shell element model
Nodes: 11.5 k
Elements: 10.4 k
Load cases: 21
Original set of results: element stress, element stress, element internal forces, SPC forces, displacements
Compact file set of results: element stress, element stress, displacements
OP2 Size: 100 Mb
SHP (1): 63.2 Mb
SHP (2): 34.0 Mb
SHP (3): 62.5 Mb
SHP (4): 62.5 Mb
SHP (5): 33.4 Mb
Model 3: Abaqus Solid Model
Description: first order brick elements
Nodes: 116 k
Elements: 143 k
Load cases: 3 steps, 63 total frames
Original set of results: stress, strain, invariants, contact forces, displacements, default history outputs
Compact file set of results: 1 step, 20 frames, displacements, stress and strain invariants
ODB Size: 7.5 Gb
SHP (1): 1.6 Gb
SHP (2): 984.7 Mb
SHP (3): 437.0 Mb
SHP (4): 437.0 Mb
SHP (5): 257.7 Mb
where the following settings have been used when saving in Shaper Compact Format (*SHP):
- compact format=Off – single precision=Off – reduced order=Off
- compact format=Off – single precision=On – reduced order=Off
- compact format=On – single precision=Off – reduced order=Off
- compact format=On – single precision=Off – reduced order=On
- compact format=On – single precision=On – reduced order=On
This post briefly presents the different options made available by the CAE Viewer and Shaper to export and share loaded models using a compact and portable binary format. File contents and format can be tuned to save progressively less information. As an example you can opt to save only visible faces instead of the full set of elements defined in the models. Similarly numerical precision can be tune to move from single to double.
Capability to reduce size of files clearly depends on selected options but also by the nature of the initial FE model. As an example, saving only free faces is very effective when dealing with solid models but has very little effect when pure shell models are considered (see example 2).