3D Orientation Data Reconstruction

This tutorial uses a Prebuilt Pipeline to reconstruct a 3D data set of a Ni based superalloy called the "Small IN100" data set. This data set was collected by M. Uchic et. al. at the Air Force Research Laboratory (AFRL) and is provided to the DREAM.3D community as a learning tool. The data set consists of 117 slices of EBSD data where each slice is 189 x 201 scan points.

Downloading the Example Data

Download the compressed archive named "SmallIN100.zip" from the DREAM.3D nightly downloads web site. After downloading the archive, unzip the files and place the "SmallIN100" folder into the DREAM.3D Data folder. The Data folder should be located at the same level as your DREAM.3D executable. The resulting folder hierarchy is exactly as follows:

DREAM3D-XXXX
    Data
        SmallIN100
        Slice_1.ang
            Slice_2.ang
            ...

The .ang files should be numbered from 1 to 117.

Convert the .ang Files to an H5EBSD Archive

The first step is to convert the text based set of .ang files into a single binary archive file based on the HDF5 file specification. In order to do this, run a Pipeline with a single Filter, the Import Orientation File(s) to H5EBSD Filter. The easiest way to do this is to use a Prebuilt Pipeline that has all the proper settings ready to use. Simply find the Prebuilt Pipeline named (01) SmallIN100 Archive in the Prebuilt Pipelines View and double click on it. This will open that Pipeline in a new DREAM.3D window. Assuming you have placed the .ang files in the correct location, all the parameters for the Filter should be set correctly, and you can simply click Go to execute that pipeline. The output H5EBSD file will be stored in the Data/Output directory.

Note that if you are attempting to import a stack of EBSD data other than the Small IN100 data set, the (01) SmallIN100 Archive Pipeline will not generally have the correct settings enabled. Instead, you will most likely have to modify the parameters of the "Import Orientation File(s) to H5EBSD" Filter to get the correct settings. Consult the "Import Orientation File(s) to H5EBSD" documentation for details. Pay special attention to setting your reference frame!

Running the Reconstruction

A complete Prebuilt Pipeline has been provided that reconstructs the Small IN100 dataset. Find the Prebuilt Pipeline named (10) SmallIN100 Full Reconstruction in the Prebuilt Pipelines View and double click on it to open the Pipeline in a new DREAM.3D window. This Pipeline should have all the correct Filters and settings for an ideal reconstruction of the Small IN100 data set. Simply click Go and allow the Pipeline to finish. It will write a .dream3d file and a .xdmf file to the Data/Output directory. More on the use of the .xdmf file can be found in the Visualizing the Microstructure section below.

The actual components of the Prebuilt Pipeline are important to understand if you plan to deal with novel data in the future. After importing the H5EBSD file using the Read H5EBSD File Filter, a first general step is to create a mask that defines which voxel elements are "good" and which are "bad". Most experimental approaches will leave data points that are definitely not part of the actual material, or were simply unable to be measured. For example, the experiment may have overscanned the specimen, resulting in extra regions of data with no material. To flag these "bad" points, use the Threshold Objects Filter, which will apply a set of user-defined logic checks to create a boolean mask array. This array is necessary for many of the cleanup and reconstruction filters in DREAM.3D. After obtaining this mask array, the next general step is to align the 2D slices. Alignment is usually necessary since specimens can move slightly during an experiment, causing drift between slices. DREAM.3D provides several different Filters to enable alignment. The user may then wish to apply cleanup routines, such as Replace Element Attributes With Neighbor Values. Once sufficiently cleaned, it is time to segment the data elements into Features. For EBSD data, it is often best to segment features by misorientation. This process should identify the grains within the microstructure. Equipped with a reconstructed set of 3D Features, the user is now free to use DREAM.3D to analyze the Features, interrogating their shapes, sizes, etc. Finally, you can save your data for later use and visualization by running the Write DREAM.3D Data File Filter. Note that this general workflow is flexible, and should be modified depending on the underlying data being processed. A good place to learn more about the individual capabilities of Filters during the reconstruction process is the Filter Documentation, especially the Reconstruction, Processing and Orientation Analysis sections.


General Workflow for EBSD Reconstruction


Visualizing the Microstructure

After reconstructing the Small IN100 data set, ParaView can be used to display the generated microstructure. Start by launching ParaView and then opening the Xdmf file that was generated as part of the pipeline. The name of the Xdmf file will be the exact same as the DREAM.3D file except for the .xdmf file extension. After opening the Xdmf file and clicking the Apply button, the user should make a few selections within ParaView in order to render the reconstructed volume:

  1. Select the Surface rendering type
  2. Select the IPFColor to color by
  3. Click the Gear icon to activate the advanced rendering options
  4. Uncheck the Map Scalars option

At this point the reconstructed volume will be mostly black. This is because the black voxels were outside of the scan area and have been marked as "bad" data. The Generate IPF Colors Filter keyed off this "bad" data and gave those voxels a black color since black is impossible to have on the IPF color scale.


Initial Rendering of the Reconstructed Small IN100 Data Set Showing Bad Voxels in Black


In order to visually reveal more of the inner structure of the reconstructed volume, the user should perform a Threshold filter within ParaView. Click on the Threshold icon in the toolbar (circled in red). The user should select the Mask to threshold on and set the range from 1 to 1. Once ready, click the Apply button. When the filter completes, the reconstruction volume will be shown without the black voxels in view. If you select to color by IPFColor again, don't forget to uncheck the Map Scalars checkbox to have ParaView use the DREAM.3D generated colors.


Applying the Threshold Filter Using the Toolbar


Visualizing the EBSD Data