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BMPRegion Command

Material points are normally added to an MPM analysis by using a series of Region commands. For FEA analyses, the object is usually defined by a series of Area commands. Both MPM and FEA can define parts of the object using image files or data in text files using BMPRegion commands.

A BMPRegion command reads a gray-scale BMP file or a text file containing numbers as gray-scale intensities from 0 to 255. This command then assigns material points or FEA element properties according to intensities in the file. Between the BMPRegion command and the subsequent EndRegion command, are a series of commands to define the file data and to map intensities to different material types. An optional second file can be a mask BMP or text file with intensities that determine the material angle for anisotropic materials. A subordinate Intensity command will map those intensities to different angles.

The structure is:

BMPRegion (bmppath),(width),<(height)>,<(scheme)>,<(anglepath)>,<(prop),(value)>...
  (one Origin command to map image origin to the grid)
  (Intensity commands to to map materials and angles to gray levels)
  (optional Rotate commands for anisotropic material angles)
EndRegion

where

If you set the "res" in a BMPReion that differs from the default setting, the code will no longer check to make sure particles are not overlapping. The user is therefore responsible using images with non-overlapping material points. Note also that this setting can use any valid number per element side and is not limited to the values allowed when choosing the default setting.

Notes

  1. In 2D problems, a BMP (or text) file maps points onto the x-y plane. Several images can be used and they combine on the same plane. In 3D MPM problems, each image (or text data) maps points onto an x-y plane at some specified constant value of z. A series of files, like slices in X-Ray CT scan data, can be combined to build up a 3D object.
  2. You can also build a model by superposing multiple BMPRegion groups on the same block of space. The subsequent files will only fill space that was not filled by prior images (provided "res" does not differ from the default setting).
  3. When using anisotropic materials, Rotate commands within a BMPRegion block can apply transformations to the material axes to define initial orientation of selected material points in the body. Rotations set using this command will override angles set in Intensity commands, but will be overridden by angles set with a mask BMP (or text) file used to map material angles. Furthermore, Rotate commands can only be used in BMPRegion blocks when doing MPM analyses.