HDF5

DAWN can open HDF5 files and makes full use of the lazy approach to loading data that is one of the key benefits of HDF5. DAWN also has a very frequent releases and uses a very up-to-date version of the HDF5 library (supporting SWMR and virtual datasets), and includes a number of filters for decompression.

The DataVis perspective in DAWN can be used as an alternative to HDFView, and supports viewing the HDF5 tree as well as advanced visualization of HDF5 datasets (taking slices, rendering as volumes, taking views of slices, plotting against other views…).

DAWN works well with multidimensional datasets, having visualization modes specifically for 1, 2, 3 and 4 dimensions datasets, that also work for slices of higher-dimension datasets.

NeXus

NeXus is a common data format for neutron, x-ray, and muon science. It is being developed as an international standard by scientists and programmers representing major scientific facilities in order to facilitate greater cooperation in the analysis and visualization of neutron, x-ray, and muon data. NeXus is based on HDF5 but uses a standardized attribute tagging system to give coherent structure to the HDF5 tree, using the concept of base classes and application definitions.

DAWN parses NeXus tags and supports NeXus in the following ways:

• DataVis:
  • Uses the @default tag in NXentry and NXroot to determine which dataset to show as default
  • Uses axes and axis attributes to determine the correct axes to use for a signal dataset
• Mapping:
  • Finds all NXdata groups and looks at the (post-2014) axes tag structure to determine if the file contains grid scan data
  • Uses the axes and _indices tags to identify non-grid scan mapping scans (i.e. spiral, or line scans) for remapping onto a grid
  • Uses the @interpretation tag to identify RGB images
• Processing:
  • Outputs NeXus as standard, recording the complete processing chain and parameters in NXprocess
  • Parses the @depends_on transformations of the NXmx application definition, found in the NXdetector, to determine 2-theta or q values of the pixels in 2D diffraction detectors.
• Powder Calibration:
  • Saves the calibration result in an NXmx compatible NXdetector