INPUT FILES¶

VTK files¶

The input file(s) materialID.vtk and/or zoneID.vtk are integer fields defined on a uniform grid according to the vtk simple legacy format (http://www.vtk.org/VTK/img/file-formats.pdf).

As described in GEOMETRY : UNIT-CELL DESCRIPTION, all the voxels with a common materialID value define a material domain. Within a given material, all the voxels with a common zoneID value define a zone.

VTK files, with float or double precision can also be used to define Initial Internal Variables.

Finally, the same VTK file format is used by AMITEX_FFTP to output fields (stress, strain, internal variables…) with the float precision.

CONSTRAINTS FOR THE GENERATION OF VTK FILES

Data definition

The materialID field must contain integers starting from 1 to N (N=number of materials), increasing without any skipping value.

Within each material domain,the zoneID field must contain integers starting from 1 to N (N=number of zones), increasing without any skipping value.

In both cases, definitions starting from 0 to N-1 are accepted but not encouraged.

VTK file headers

The VTK file header must strictly contain the following 10 lines:

# vtk DataFile Version 4.5
Materiau
BINARY
DATASET STRUCTURED_POINTS
DIMENSIONS    66   66   66
ORIGIN    0.000   0.000   0.000
SPACING    1.000000    1.000000   1.000000
CELL_DATA   274625
SCALARS MaterialId unsigned_short
LOOKUP_TABLE default

DIMENSIONS defines the number of voxels per side plus 1. Here, the grid consists of 65x65x65 voxels.

SPACING defines the voxel size and especially the voxel shape. Here voxels are cubic.

CELL_DATA is the number of voxels, it must be in agreement with DIMENSIONS, here 274625=65x65x65.

SCALARS defines the data type (char, short, int, long, unsigned_char, unsigned_short, unsigned_int, unsigned_long, respectively coded on 1, 2, 4 and 8 bytes), here the type is unsigned_short (2 bytes).

Binary data

Binary data, given just after the header, must satisfy the following constraints:

byte ordering used to write the binary data is big endian
the data type when writing binaries must be consistent with the data type given in the header
the maximum field value (especially for zoneID) must be less than the limit value corresponding to the data type

MATLAB/OCTAVE functions can be found in Tools to generate VTK files compatible with AMITEX_FFTP.

Caution

In case of unsigned data types, the limit value used by AMITEX_FFTP is the limit value for corresponding signed data types (~ 0.5 x limit value for unsigned).

For example, the maximum value for both char and unsigned_char data types (coded on 1 byte) is 127.

TIPS

You can use specific Tools to generate vtk files for AMITEX_FFTP
if PARAVIEW can’t read your vtk file don’t go further with AMITEX_FFTP.

XML files¶

Of course, XML files must follow the XML syntax (use a XML editor with syntax coloring to detect syntax errors).

A comment is written like this:

<!-- A comment -->

There is no need to follow any specific order for the various inputs given in XML files.

Case sensitivity rules

XML is a case sensitive language. The name of XML nodes and attributes are case-sensitive.

However, the name of the string variables that can be input between quotation marks are case insensitive.

Hence, in the following XML line

<Coeff Index="1" Type="Constant_Zone">

Here, Coeff is a node, Index and Type are attributes : they require the uppercase “C”, “I” and “T”.

However, the string Constant_Zone can be read constant_zone in AMITEX_FFTP.

Exception : path names are case-sensitive.

BIN files¶

BIN files are used to introduce per zone material coefficients or initial internal variables (see Material Coefficients), or composite voxels properties (see COMPOSITE VOXELS (ADVANCED USERS)).

The header must contain the following 2 lines:

2
double

The first line is the number of binary values within the file, it must greater or equal to the number of zones defined in the VTK file.

The second line defines the data type (char, short, int, long, unsigned_short, unsigned_int, unsigned_long, respectively coded on 1, 2, 4 and 8 bytes, or float and double on 4 and 8 bytes), here the type is double. The rest of the file should be binary data satisfying the constraints defined in Binary data (big endian ordering and maximum values).

MATLAB/OCTAVE functions can be found in Tools to generate BIN files compatible with AMITEX_FFTP.