BMPRegion Command

An advanced feature of NairnMPM is that you can create material property directly from images.

BMPRegion Commands

In scripted files, an image is converted into material points using:

BMPRegion (bmpPath),(width),<(height)>,<(anglesPath)>
  Origin (xO),(yO),<(zO>,<(flip)>
  Intensity (matID),(grayMin),(grayMax),<(prop),(value)>,...
    . . .
  Intensity "angles",(gray1),(gray2),(angle1),(angle2)
  (optional rotation command)
EndRegion

In XML files, the command block is

<BMP name="(bmpPath)" width="(width)" height="(height) angles="(anglesPath)>
  <Origin x="(xO)" y="yO" z="zO" flipped="(flip)"/>
  <Intensity mat="(matID)" imin="(gramMin)" imax="(grayMax)">
     (property command options)
  </Intensity>
    . . .
  <Intensity imin="(gray1)" imax="(gray2)" minAngle="(angle1)" maxAngle="(angle2)"/>
  (optional rotation commands)
</BMP>

where

• (bmpPath) is the full or relative path name to the BMP file. The file must be an uncompressed, gray-scale, BMP file with 8 or less bits per pixel. The most useful is an 8-bit file with 256 levels of gray.
• (width) and (height) specify the width and height for the image, but there are several ways to specify them.
• (anglesPath) is an optional full or relative path name to a mask BMP file whose intensities determine the material angle for rotation about eh z axis when setting anisotropic material points. The file must be an uncompressed, gray-scale, BMP file with 8 or less bits per pixel. The file must be exactly the same size (horizontal and vertical pixels) as the image file in (bmpPath).

Inside BMPRegion block, you include various commands to determine how the pixels are converted into material points. The possible subordinate commands are:

• Origin command - used to connected the image coordaintes the the MPM grid coordinates.
• Intensity command - used to determined conversion of gray scale values in the images into material points or rotation angles
• (optional rotation commands) - these optional commands provide alternative methods for setting initial material orientation when modeling with anisotropic materials.

Image Width and Height

The (width) and (height parameters specify the width and height of the image, but they can be specified using different styles. The options are:

1. Give both as positive numbers - if both numbers are provided and positive, they give width and height of image in mm (in XML files, a units attribute can change the units). They need not match the actual image, but if they are different, the image will be scaled.
2. Give only one as a positive number -

BMPRegion #1,3.4 - if only width is given, the height is calculated from the aspect ratio of the BMP file. BMPRegion #1,-1e9,5.6 - if only height is given, the width is calculated from the aspect ratio of the BMP file. To specify only height, the width has to be more negative than -1e8. BMPRegion #1,-.0013,-.0013 - if either the width of the height is negative (and greater than -1e8), the absolute value is taken as the number of mm per pixel and the width or height is calculated from the size of the BMP image. Any of first the three previous options for specifying width and height can replace a positive dimension with a negative value to indicate mm per pixels. (note: when a second file is specified in scripted files, both (width) and (height) must be entered to preserve argument numbering, but either one can be -1 to preserve aspect ratio).