Useful macros

This directory contains a set of useful macros. To learn what a specific macro does, see the comment for the macro (which is accessible either from the Help..Application Comment option, or from the Open File dialog box).

A few of these macros require data sets to be Import'd. These data sets are located in ../data.

Directory name: contrib/macros

Other files in this directory:

• AntiAlias.net (view/run it)
  This macro will create an anti-aliased version of your image. It has as inputs the object to be rendered (typically whatever you are passing to the Image tool), along with the camera used for your desired view (the second output of your image tool). You can also choose whether or not to write out the anti-aliased image to a file.

  Note that screen objects (captions and colorbars) will end up half as large in the anti-aliased version of the image. Thus you should increase the "height" parameter of a caption or the "shape" parameter of a colorbar by a factor of 2 before passing the collected object to AntiAlias.

  Also note that lines (showconnections, for example, or line fonts) will tend to become dimmer after passing through the anti-aliasing process. You may want to brighten the colors first using Mark(object,"colors")-> Compute(2*a) ->Unmark(object).

• AutoRegrid.net (view/run it)
  Given a set of scattered points, this macro interpolates the scattered points onto a regular grid computed from the bounding box and the number of points using Regrid. Refer to the description of Regrid for more information.

• BandColors.net (view/run it)
  This macro takes as input a 2D scalar field, a scalar list with n items and a list of colornames with n+1 items. It creates as output a banded version of the 2D field, colored using the list of given colors from min_of_data to max_of_data. As a second output, it gives the colormap, for use with the ColorBar module, for example.

  This macro requires the macro ConvertColorNameList, also found in this directory.

• CDF_EPOCHbreakdown.net (view/run it)
  Converts a CDF EPOCH into its component parts as Import'd by DX as the position value for a series.

• CDF_GlobalAttributes.net (view/run it)
  Extracts NSSDC standard CDF Global Attributes as Import'd by DX.

• CDF_VariableAttributes.net (view/run it)
  Extract NSSDC standard attributes for a CDF variable as Import'd by DX as field attributes.

• Clock.net (view/run it)
  Creates a clock with a single sweep hand with the hand at a specific position. The color and opacity may be specified. The range in value corresponding to a full sweep may be specified.

• ClosedIsosurface.net (view/run it)
  This macro "caps the holes" in an isosurface. These holes may be present if the isosurface intersects the boundary of the data set. The macro uses ShowBoundary, Band, and Include to determine the necessary caps for the isosurface. The user needs to specify whether the "inside" of the isosurface contains values larger than, or smaller than, the isovalue given.

• ComputeGroupMemberMeans.net (view/run it)
  Given a group or series, creates a list of the mean values of each member.

• ConvertColorNameList.net (view/run it)
  This macro takes as input a list of colorname strings (such as "red", "linen", "cyan", "light goldenrod", etc.) and converts it to a list of rgb vectors.

• ConvertToCellCentered.net (view/run it)
  This program converts a field from positions-dependent to connections-dependent without interpolating data as would be the case for Post. This program is intended to be used for cases where data can only be imported as positions-dependent because the original structure does not make a distinction between positions-dependent and connections-dependent and Data Explorer assumes a default of positions-dependent (i.e., CDF, netCDF and HDF). Since that information is not typically imbedded in the file, only the user would be aware that such a transformation would be required. In such cases, the bounding box for the data is not exactly correct, which Post preserves. This program would make the appropriate adjustment. This problem occurs often for gridded observational data in the earth and space sciences.

• Decrement.net (view/run it)
  This simple macro simply decrements a value by 1.

• Equals.net (view/run it)
  This simple macro outputs 1 if two inputs are equal, and outputs 0 otherwise.

• ExtractBoundingBox.net (view/run it)
  Extracts and separates the coordinates of the bounding box of an object.

• FindPosWithLargestData.net (view/run it)
  This macro, given a data field, extracts the position(s) associated with the largest (or smallest) data value(s).

  If you know that only *one* position has the extreme data value, this macro could be simplified a great deal, removing all the get and set pairs and simply outputing the outputs of the two Selects near the left side of the macro, with the which parameter of the Selects set to 0.

  Sort is used to first sort the data field by data field, in either descending or ascending order. Thus the extreme data values are all near the beginning of the data component. The associated positions are of course also now at the beginning of the positions component.

  There are several Get/Set pairs in this macro. One holds a counter for selecting from the data and positions components. Another holds the last data value, for comparison with the current value. This will control the termination of the macro. Another two Get and Set pairs are used to create the list of data values and list of positions, for the situation when there is more than one extreme data value.

• GreaterThan.net (view/run it)
  If the first input is greater than the second input, this macro outputs 1. Otherwise it outputs 0.

• Increment.net (view/run it)
  This simple macro increments a value by 1.

• IsoColor.net (view/run it)
  This macro creates a combined realization of pseudo-colored (AutoColor) contour lines of specified increment and range overlaid on a pseudo-color image of a scalar field. Either technique or both may be the result. Data may be treated as either connection- or position-dependent.

  IsoColor provides the user with less flexibility and fewer options than does the macro IsoImage.

• IsoImage.net (view/run it)
  This macro creates a combined realization of pseudo-colored contour lines of specified increment and range overlaid on a pseudo-color image of a scalar field or filled contours. Outputs include the pseudo-colored field only, contour lines, and the colored field combined with contours, Data may be treated as either connection- or position-dependent for the pseudo-color image. The user provides colors for the contours and image.

• JulianDayToMonthDay.net (view/run it)
  Given a year and Julian day for that year, a year, month and day of month string is created in two formats: dd-mmm-yyy and yyyymmdd, where mmm is a string month (i.e., Jan, Feb, etc.) and mm is the month number.

• Laplacian.net (view/run it)
  The Laplacian of a scalar field is computed by computing the gradient of the field and dotting the resultant vector field with itself.

• MakeBox.net (view/run it)
  The macro accepts as input an [x, y] location and [delta_x, delta_y]. The former is used to define the center of a rectangle. The latter is used to define the size of the rectangle. The user can also specify the color of the rectangle, which will consist of lines.

• MakeOneField.net (view/run it)
  If you are importing data using the general array format, and you specify that there are "n" different fields in the file, it will be imported as a group with "n" members.

  This macro converts this group into a single field, with a number of components, where the component names are the given field names. This is sometimes a more useful structure. Note that you will generally need to use Mark to mark a particular component as "data" in order to use most DX modules, which expect the data to be in a component named "data".

• MapOnStates.net (view/run it)
  This macro maps a given field onto the 48 continental states in the U.S. It is assumed that the positions of the input field contains a list of the integers 0 to 47, where each integer represents one of the 48 states in strict alphabetical order. The data component of the input field will be mapped onto the shapes of the states.

• Not.net (view/run it)
  If the input is non-zero, this macro outputs 0, else it outputs 1.

• ReduceTriangles.net (view/run it)
  Does a crude simplification of a triangular mesh to provide the "equivalent" of Reduce for unstructured meshes.

• ReverseFrontAndBack.net (view/run it)
  This program reverses the front and back faces of an object. This program can change both the direction of the normals and the orientation of the connections. By default it assumes that the normals and the connections of the input object are already consistent with one another (see the discussion of "Standard Components" in Chapter 3 of the Data Explorer User Guide). Therefore as it flips the connections (which changes the definition of "front" and "back") it also flips the orientation of the normals. If your normals are *not* consistent with the orientation of your connections, then you should set the "reverse_normals" parameter of this macro to 0.

• ShowBackSides.net (view/run it)
  This macro, given a 3D data set with regular connections, returns just three sides of the boundary of the data set. This is sometimes useful as a "backdrop" for other realizations in a data set, such

• StreamlineArrow.net (view/run it)
  Generates streamlines, optionally colored (e.g., fixed or pseudo-colored by magnitude), which show the direction of the vector field with small arrows. In some sense, this tool emulates the well-known and venerable STRMLN function of NCAR graphics. Currently this tool only operates correctly with 2d vector

• SubSample.net (view/run it)
  Subsamples a field with regular connections as a way of reducing the resolution. It will be faster than Reduce, but will not do interpolation. Hence, there will not be smoothing, but some local information will be lost. The field may be sampled uniformly along each axis or at a different level for each dimension.

• SumList.net (view/run it)
  This macro accumulates the values in a list.

  The user specifies the list and an initial value for the accumulation (which defaults to 0). The accumulation is automatically reset each time the macro is rerun.

• SurfaceFlux.net (view/run it)
  Given a surface and a vector flux field, this macro computes the integrated flux through the surface. The user has the option of reversing the sign of the flux through a third parameter (the default behavior is that positive flux flows through connection elements from "back" to "front" as defined by the orientation of the connection elements).

• TextureMap.net (view/run it)
  

  This macro takes a rectangular surface and an image and arranges it so that the image is texture mapped onto the surface at rendering time. The detail in the final picture is obtained from the image which is input to this macro, not from the number of quads in the input surface. To see a texture mapped image you must be using the hardware rendering option in the Image macro, and you must be running on a system which supports texture mapping (currently systems which use OpenGL for rendering - the dec alpha and ibm6000s with OpenGL support. See the -hwrender option of the dx command by running "dx -morehelp" for more information on ibm6000 options.)

  The first input to this macro is the rectangular surface to be shown. The second input is the orientation of this surface. It is a number between 0 and 7; see the Reorient module for an explanation of how to specify a specific orientation (or just try some numbers out). For good performance there should be as few quads in the surface as possible - use Reduce before putting the surface into this macro to reduce the number of quads. The surface can be a single quad constructed with the Construct module; this will have the best possible performance.

  The third input is the image to be mapped onto the surface. The fourth input is the orientation of this image relative to the surface. Again, see the Reorient module for an explanation of how to specify orientations.

  The last input controls the size of the texture map. The input must be a number between 6 and 12 (default 7) which specifies what power of 2 the size will be. 2**6 is 64, 2**7 is 128, etc. Since hardware requires that the texture map be a power of 2 in resolution, this macro resamples the image into a 32x32, 64x64 etc image. The original image can be any size. The smaller the size of the texture map the faster the rendering, with some loss of precision relative to the original image. There is usually a limit in the hardware card for the maximum size of a texture map; if the size exceeds that limit the rendering will either fail or will become drastically slower as main memory may be used instead of memory local to the hardware rendering card.

  If the surface is to be deformed, the texture must first be mapped to the flat surface and then the RubberSheet module can be used to deform the underlying surface. If the resulting image looks bright with no relief discernable use the Shade module to enable shading. If the image then looks dark, it may be because the hardware card is interpreting the front of the image as the back. Use the following sequence of 3 modules to invert the shading: Mark(object, "normals") -> Compute(object, expression="-a") -> Unmark(object). Use this sequence after the Shade module and before the Image module.

• TranslateToOrigin.net (view/run it)
  This simple macro translates an object to the origin, so that if you use Rotate, the object will rotate about its center.

• UniformSample.net (view/run it)
  This macros samples the selected manifold at a set of more-or-less uniformly spaced samples on a surface of quads or within a volume of cubes. The parameter density, which is the approximate number of points that result, controls the spacing of the samples. The method by which the sample points are selected is different than that of Sample, which does not always produce a uniform distribution. The output of this macro is a set of unconnected positions. Any components in the original field manifold that are dependent on either positions or connections are mapped onto the resulting samples. In either case the dependency of the component in the output field will be dependent on the positions.

• UnsquishGlyph.net (view/run it)
  Often people are visualizing data which has vastly different extents in the different dimensions. Scale is used to modify the appearance of the final image. If Scale is used immediately prior to the Image tool, then any AutoAxes used will display the correct, unscaled values along the axes. Unfortunately, if glyphs are used in the image, the glyphs will be scaled as well, and will show up as "squished".

  This macro provides a simple solution for the "squished glyph syndrome". You give the macro the scale factor which you plan to use for the entire image. The macro produces an inversely squished glyph which you in turn give as a "user-given glyph" (see the man page for AutoGlyph if you're interested). Simply pass the output of the macro to the second tab of Glyph or AutoGlyph (the "type" parameter.

  You need to tell the macro whether you want a scalar or vector glyph, and the "quality" of the glyph (a number from 0 to 1, or one of the defined glyph types (again, see the AutoGlyph man page).

• VolumeIntegrate.net (view/run it)
  Given a volume and a scalar field, this macro computes the integrated field within the volume.

  Note that if you just want the volume contained within a surface, the Measure module will do this.

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