5.1. Directions For Writing Your Own UDW

Create a directory where your writer will be located, for example
$CEI/ensight251/src/writers/mywriter/
Several example writers are provided which have source code and a Makefile.
For example, look at the flatfile format, an ASCII comma delimited writer.
cd $CEI/ensight251/src/writers/flatfile
Notice that there are several files in this directory.
- libuserd_write.c - The writer code
- Makefile - makefile
- README - specific directions for using this writer

Copy these files into your directory:

$CEI/ensight251/src/writers/mywriter/

The Makefile should be used to compile and link a shared library.
Edit the Makefile so that it names the shared library properly.

Edit the C file.

give the writer a name. Ignore the other returned variable.
give the writer a version so you can use version control in the future revisions

The UDW routine called by EnSight. What you do in here is up to you; but basically you can open a file for writing, call a bunch of methods (listed below) to get the data of interest, write data into a file, and return an error status code to EnSight.

This method has the following arguments:

`char full_fname[Z_MAXFILENP]`	- (IN)	file name requested by the user from the GUI
`int lis_parts[Z_MAXPART]`	- (IN)	list of parts selected by the user in EnSight
`int num_parts`	- (IN)	number of selected parts
`int do_binary`	- (IN)	TRUE if writing binary file FALSE if writing ASCII file
`float max_fsize_mb`	- (IN)	maximum file size value for this machine
`int combined`	- (IN)	TRUE if user requests single file output FALSE if user allows multiple file output
*`float timestep_vals`**	- (IN)	array of time step values
`int ntime_steps`	- (IN)	number of time steps
`char text_input[ UDW_STRSIZE]`	- (IN)	string entered from GUI by user can be used to input commands to modify writer behavior
*`int error_flag`**	- (OUT)	Return from writer Z_ERR if a problem Z_EN_ERR_NONE if no problem

Edit the README file
Since each writer can operate however it wants, document any constraints, expectations, limitations, user specified parameters, etc, here. Given this is likely the only documentation available for the writer, give enough details about it for both end-users and future maintainers.
Set the UDW environment variable:
setenv ENSIGHT10_UDW $CEI/ensight251/src/writers/mywriter/
EnSight will first look in $ENSIGHT10_UDW and load the writer library. Next, EnSight will then look in $CEI/ensight251/machines/$CEI_ARCH/lib_writers/. If duplicate writers are found, they will only be loaded once.
Make your library and fix all compile errors.
Run the EnSight using a manual connection and specify the command line option -writerdbg to the server to verify that it is loading the UDW correctly at runtime:
ensight251_server -writerdbg ( or for Windowsensight251_server -writerdbg)
Compile in UDW debug output to track the progress of runtime loading of the writer and proper operation.

Topical List Of User-Defined Writer API Methods

The following is a topical list of the User-defined Writer API methods along with a brief description of each. These methods should be called from within the UDW's () method to retrieve data from EnSight.

General Info
USERD_writer_part_verify	Good part if at least one part > 0 Is at least one part created geometry? (Not discrete and not model part) Do I need to write model geometry? (not discrete particle type) Do I need to write measured geometry? (discrete particle type)
USERD_get_undef_ptr	Checks each element type for any undefined variable values
USERD_get_num_time_steps	Return the time-set num steps index based on var_index and meas_data
USERD_writer_get_variable_transient	Returns variable static (0) or transient (1)
USERD_writer_get_var_type	TRUE if model vars = static && measured vars = constant
Variable Info
USERD_writer_get_undef_val	Echoes the EnSight undefined value
USERD_writer_get_exist_active	Does var exist and is it active?
USERD_writer_get_variable_info	Gets variable descriptors source, complex, type, descrip, vref, freq, parent
USERD_writer_get_part_const_value	Gets the value of a per part constant
USERD_writer_get_per_elem_node	Gets per element or per node flags, any undefined flag
USERD_writer_get_number_of_variables	Returns number of variables
USERD_writer_get_measured_vector_var_val	Returns vector of measured variable values
USERD_writer_get_part_variable_status	T or F, does part have variable(s)?
USERD_writer_get_static_const_value	A variable's current constant value
USERD_writer_get_component_vector_var_val	Returns vector of variable value
Part Info
USERD_writer_get_part_info	Gets part_type, num elems, descrip, struct_flag
USERD_writer_get_part_struct_unstruct	Returns either structured or unstructured
USERD_writer_get_changing_measured_geometry_flag	Measured geom change status
USERD_writer_get_changing_model_geometry_flag	Coord, connect change status
USERD_writer_get_structured_data	Gets values assoc w/ struct data part_ijk_num, iblank nf, ghost flag, cell type
USERD_writer_get_structured_data_ijk	Gets values assoc w/ struct data part_ijk_num, iblank nf, ghost flag, cell type
USERD_writer_get_structured_cell_type	Gets only the cell type for structured data
Nodal Info
USERD_writer_get_node_label_status	Does MODEL have node labels?
USERD_writer_get_part_node_label_status	Does PART have node labels? (T or F)
USERD_writer_get_part_coords	Gets part x, y, & z coordinates in 2d format
USERD_writer_get_part_coords_vector	Gets part x, y, & z coordinates in vector format
USERD_writer_get_part_implicit_coords	Gets structured part ijk implicit coordinate data
USERD_writer_get_part_node_id	Gets part node ids
Element Info
USERD_writer_get_part_element_size	For a given element type, return the number of nodes in the element
USERD_writer_get_part_element_connectivity	Get the elemental connectivity for a specific part and a specific zoo element type
USERD_writer_get_part_nsided_connectivity	Get the N-Sided element connectivity
USERD_writer_get_part_nfaced_connectivity	Get the N-Faced element connectivity
USERD_writer_get_element_label_status	Does MODEL have element labels?
USERD_writer_get_part_element_label_status	Does PART have element labels? (T or F)
USERD_writer_get_part_elem_id	Returns array of element id's
USERD_writer_get_part_elem_id_per_type	Returns array of element id's per elem type
USERD_writer_get_eletype_string	Get the string describing that element type
USERD_writer_get_element_connectivities_for_part	Elem connectivity vector
USERD_writer_get_element_connectivities_for_part_simple	Elem connectivity by elem type
USERD_get_Nfaced_size	Total vector length, index of first connectivity val, max conn size, total # faces
USERD_get_Nfaced_vector	Gets vector of connectivity data
Time
USERD_writer_validate_time_step	Validates the current EnSight time step for multiple scales
USERD_writer_get_original_time	Gets client time which is the original time.
USERD_writer_set_current_time	Sets the time
Other
USERD_get_titles	Gets the two model title description lines
USERD_writer_get_ensight_release	Get EnSight release letter as string
USERD_writer_get_ensight_version	Get EnSight version number as string
USERD_writer_whatis_machine_byte_order	Current machine is big- or little-endian
Sizing
USERD_writer_get_var_max_sect_vals	Loop thru parts & find max # variables of node or elem type
USERD_get_modl_geo_max_node_size	Loop thru parts & find max # of nodes
USERD_get_modl_geo_max_conn_size	Loop thru parts and find max connectivity size
USERD_get_current_model_extents	Either assign or compute model ranges
Specialized
USERD_writer_get_part_coords_per_elem	Gets part coordinates fro TRI & QUA elems
USERD_writer_get_part_coords_per_elem_border	Gets part border coords for TRI & QUA
USERD_run_border	Calls create_border and finds boundary of part