External Pixel Field#

External Pixel Field = <char_string1> {Q1|Q2} <file_name> <integer1>

Description / Usage#

This optional card format provides a mechanism for reading-in pixel fields which are converted (mapped, with a least squares algorithm) to finite element fields with the chosen interpolation. After GOMA execution these fields are output in exodusII format in a file map.exoII. Please see discussion below and Tutorial GT-038 for more details and important tips.


Name of the nodal field to be read; it should correspond to a nodal variable name you wish to have in the output EXODUS II file. If you subsequently wish to read the field in again and use as an EXTERNAL_FIELD model on other material property card, the chosen name matters.

{Q1 | Q2}

The type of interpolation to be applied to the external pixel field variable field. Possible values are as follows:

  • Q1 - Linear

  • Q2 - Quadratic


Name of the text file name with the pixel points. The pixel field format in this file should be as follows:

  • # pixel points

  • x_1, y_1, z_1 value

  • x_2, y_2, z_2 value

  • x_N, y_n, z_n value


Material block ID to which the pixel field is mapped.


External Pixel Field = HEIGHT Q1 tread.txt 1

Technical Discussion#

Please consult the tutorial GT-038 before using this capability. Many user tips are given together with a more thorough explanation on the proper use This capability is extremely memory intensive, and excessive grid sizes and pixel densities can blow out the memory on your machine. As of 12/22/2012 (the end of the Mayan calendar) these fields are used typically to bring in pattern maps for scaling porous media and lubrication height properties.

SAT, HEIGHT, PERM, CROSS_PERM, SH_SAT_CL_POROSITY, etc. These are specially designated external fields which are mapped to variations in these properties corresponding to thin porous media. Please see GT-038.


GT-038.0: Pixel-to-Mesh Tool Tutorial for GOMA. P R. Schunk, Memo to distribution, 10 November 2009.