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THERMICA Geometry Conversion

VIF-reader  module

Activation of the VIF-reader  module

The VIF reader module of TASverter can be activated from the command line using the option:


When the TASverterGUI is used, the "Model Type" of the "From" file must be set to "THERMICA SYSBAS".

When this option is activated, TASverter expects a VIF formatted file as input.

The VIF-reader  was the first module developed for TASverter. It was deliberately implemented first because of the simplicity of the VIF format. This simplicity allowed a quick implementation and verification of the reader module and served as a basis to gain experience to develop other modules. However, the accuracy that the VIF format provides for representing radiative models is limited. Therefore the user is advised to read the THERMICA SYSBAS format instead, where possible. See the SYSBAS-reader  and SYSBAS-writer  sections below for more details.

SYSBAS-reader module

General limitations

The development of this module used the THERMICA Input Language User's manual as reference. During the development, however, it became clear that several old ESABASE language constructs found in models developed by users are also accepted by THERMICA, but are not described in the manual. As a result, many small test cases had to be developed to reverse engineer the interpretation of the SYSBAS file by THERMICA. It is still possible that there are more undocumented features of the SYSBAS language than were discovered during this testing and that will not be handled correctly by the SYSBAS reader module.

All references in this help to the THERMICA Input Language User's Manual are based on the document issue 2.0, software version 3.2 of the manual.

Activation of the SYSBAS-reader  module

The SYSBAS reader module of TASverter can be activated from the command line through the option:


When using the TASverterGUI, the "Model Type" of the "From" file must be set to "THERMICA SYSBAS" (see figure below):

Activation of SYSBAS reader through the TASverter GUI

Figure 6: Activation of SYSBAS reader through the TASverter GUI

Conversion from THERMICA SYSBAS to STEP-TAS 


The $DATA section is the start of the actual definition of the THERMICA SYSBAS model.

After processing this input two STEP-TAS  models are created: an empty geometrical model and an empty associated thermal lumped parameter model. The model id assigned to both of these models is the name of the SYSBAS file without file name extension and without the path to the directory where the file is located.

The comments preceding the $DATA section are stored in the STEP-TAS  description of these models.

The SYSBAS-reader  accepts the UNITS and SPACE parameters of the $DATA section.


The UNITS parameter specifies the unit used for all length dimensions in the SYSBAS model. This unit is converted and stored in STEP-TAS.  If the command line option --source_length_unit   is provided to TASverter this value takes precedence over the one specified in the $DATA section.

According to the THERMICA Input Language User's Manual, the UNITS parameter may have the values METER, CM or MM. INCH is also supported, but this is not documented. The SYSBAS reader module supports all these values.

The applicable length unit, i.e. either the one specified on the $DATA section or the one specified through the command line option is converted to an equivalent length unit definition in STEP-TAS. 


The SPACE parameter is accepted by the SYSBAS reader module, but is not converted to any equivalent STEP-TAS  property or entity.

THERMICA Object declaration

THERMICA objects are converted to a compound geometrical entity in STEP-TAS  that stores all the surfaces and sub-objects  with the THERMICA object. The THERMICA object identifier is converted to STEP-TAS  in the following way:

<i1, i2,...,in> becomes oi1_i2_..._in
An example

<1,5> becomes o1_5

Any surfaces within an object are identified with:


where xx is the sequence number of the surface within the object

An example: The second surface in object <1,5> gets the identifier o1_5s02.


All the documented options to define a coordinate transformation for the object through a $AXIS section are supported by the SYSBAS-reader. 


According to the documentation the $COPY section should be the first section in the object.

However THERMICA accepts any section before the $COPY section, but completely ignores these without any warning messages. The SYSBAS-reader  module reproduces this behaviour, but it does give a warning message.


The $MIRROR section is not supported by the SYSBAS-reader  module. TASverter will generate a fatal error if the input file contains a $MIRROR section. As a work-around  the $MIRROR section can be expanded by using the THERMICA software to write out the expanded SYSBAS file.


TASverter offers only limited conversion of the $INFO section. The COLOUR parameter is the only parameter that is converted. The RGB-values  of the THERMICA colour specification are stored in the STEP-TAS  dataset. The colour value is assigned to both sides of the surfaces within the THERMICA object.

The following parameters are accepted but their values are ignored without a warning message:


All documented [SYSBAS] elements of the $TSHAPE section are supported except:


Optical properties, node numbers and side activity (NRAYS = 0 or -1) are processed and converted to STEP-TAS.  The following $THERMAL parameters (mostly originating from the ESABASE language) are accepted, generate a warning message, but are then discarded:

The optical properties defined in the $THERMAL section do not have material names or identifiers. Therefore, TASverter must generate identifiers for them before storing them in the STEP-TAS  dataset. These identifiers are of the form "material_xx" where "xx" is the sequence number of the unnamed material.

Note that THERMICA also supports named materials as defined through the $D_PROPERTY section (see below).


Only the D_NAME parameter is processed. The D_MATERIAL, D_COATING, and D_BCOATING parameters are accepted but not converted.

When no D_NAME is provided by the user, or when the referenced file does not exist, THERMICA loads the default SYSMAT file from the THERMICA installation directory (MATERIAL.SYSMAT). The SYSBAS-reader  module has no knowledge of the THERMICA installation directory and assumes that it is not available. Therefore, when named materials are used through $C_PROPERTY, the parameter D_NAME must reference a local file SYSMAT file. This local file may be a copy of the file from the THERMICA installation directory.

The THERMICA material identifiers may contain '-' characters. STEP-TAS  does not allow this character to be part of an identifier, so the SYSBAS-reader  convert this character into an underscore and add a sequence number to the identifier if necessary to avoid duplicated names.

Before storing the material, the SYSBAS-reader  module verifies that the materials pass basic energy conservation tests. It appears that the material definitions with the names SUPRASYL and BK7 that are part of the SYSMAT file from the THERMICA installation directory do not pass these tests. If this SYSMAT file is used, these materials have to be removed from the file.


All parameters of the $C_PROPERTY section are accepted, but the C_MATERIAL parameter is not converted to STEP-TAS. 

When the $C_PROPERTY section is used, a SYSMAT file with named material definitions needs to be specified with the D_NAME parameter of a $D_PROPERTY section.

When either the C_COATING or the C_BCOATING parameter references a material with transmissivity values a new material is generated based on the reference materials with the transmissivity values merged into it. The SYSBAS-reader  will generate a unique identifier for the material, as described in the $THERMAL section above.

Conversion of comments

The SYSBAS-reader  converts any comments before the "$DATA" and stores them as an information attribute of the STEP-TAS  geometrical model. These comments may also be defined as a $TEXT section.

All other comments are skipped and are not stored the STEP-TAS  dataset.

The object labels are the only descriptive elements that are transferred to the STEP-TAS  dataset.

SYSBAS-writer module

Activation of the SYSBAS-writer  module

The SYSBAS writer module of TASverter can be activated from the command line using the option:


When the TASverter GUI is used the "Model Type" of the "To" file must be set to "THERMICA SYSBAS" (see figure below)

Activation of SYSBAS writer module through the TASverter GUI

Figure 7: Activation of SYSBAS writer module through the TASverter GUI

When this option is activated, TASverter generates a SYSBAS formatted file as output at the specified location.

Conversion from STEP-TAS  to THERMICA SYSBAS


The $DATA section is created with two parameters: UNITS and SPACE.

The values assigned to these parameters are the following:


The default for the generated value of the UNITS parameter is METER. This default can be overridden by using the TASverter command line parameter --destination_length_unit .  When the unit specified is one supported by the SYSBAS language, i.e. METER, CM, MM or INCH, the UNITS parameter is set to this unit and all length values within the model are scaled appropriately.

If the unit specified through this parameter is not one of the units supported by the SYSBAS language, then TASverter sets the UNITS parameter to METER, but leaves all length values within the model completely unchanged: no scaling or conversion is applied. This allows the user to view the model, albeit at the wrong size, even if Thermica does not support the desired units. TASverter includes a warning message as a comment in the generated SYSBAS file. The same warning message is written to the log-file  and the screen during the TASverter run, as shown below.

Example output from a run with --destination_length_unit=ft  is shown below:

# Destination length unit ft selected through --destination_length_unit
# is not supported by the SYSBAS language.
# Length unit conversion is applied anyhow, but $DATA parameter UNIT is set to METER


The value of the SPACE parameter is always set to 10


The SYSBAS-writer  generates a THERMICA SYSMAT file for each STEP-TAS  material environment containing optical properties.

Where more than one material environment exists, for example to represent beginning of life (BOL) and end of life (EOL) properties, the user can specify which one is active by entering a value in the Material Environment input field of the GUI. This value will be used to set the $D_PROPERTY section of the generated SYSBAS file so that it refers to the correct SYSMAT file for that environment.

The material environment can also be set on the TASverter command line by using the option:


Cutting or boolean operations

THERMICA does not currently support cutting operations. Therefore, the SYSBAS-writer  module can only output the "uncut" surface in combination with comments that define the surface that is supposed to act as the cutting tool. The purpose of the latter is to supply as much information as possible to the user for reconstructing the geometry in the SYSBAS language.

For further information and recommendations on using boolean operations, see also Cutting operations in the section on ESARAD Geometry conversion.


The colours in STEP-TAS  are defined by specifying their RGB-values.  Colours are matched by comparing RGB-values  with each other. The THERMICA colour with the closest match to the provided STEP-TAS  colour is assigned to the object.

In the STEP-TAS  dataset different colours can be assigned to both sides of a surface. The THERMICA SYSBAS language provides the option to provide only one colour. The generated SYSBAS contains a colour specification for each object. If the positive side of a surface is active (POS) or both sides of a surface are active (BOTH), the colour of positive side will be written to the generated $INFO section, otherwise the colour of the negative side (NEG) is written.

Non-matching  thermal node meshing

The thermal node meshing on the THERMICA surfaces is defined in certain parametric directions depending on the surface type. The thermal node numbers on the surfaces are defined using these meshing directions and a node number specification consisting of a base node number and a node number increment. The THERMICA SYSBAS language only allows for specification of the same thermal node numbers on both sides of a surface (see also next section). When the meshing for a surface as defined for the STEP-TAS  representation cannot be represented by a base node and a node increment, the SYSBAS-writer  module generates an equivalent set of single node sub-surfaces. 

Different nodes on both sides of same surface

The THERMICA SYSBAS language only allows for specification of the same thermal node numbers on both sides of a surface. When a STEP-TAS  surface has different node numbers on different sides of a surface, this cannot be represented by a single THERMICA surface. In that case, two surfaces are generated in the SYSBAS file. Both surfaces have only one active side and thy are separated from each other by a small gap.

The user can set this gap by entering a value in the Double Sided Gap input field in the TASverterGUI, or passing the following option on the TASverter command line:


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