2.3.3.3.158. NXmicrostructure_ipf

Status:

base class, extends NXprocess

Description:

Base class to store an inverse pole figure (IPF) mapping (IPF map).

Symbols:

n_z: Number of pixel along the z slowest direction.

n_y: Number of pixel along the y slow direction.

n_x: Number of pixel along the x fast direction.

n_rgb: Number of RGB values along the fastest direction, always three.

Groups cited:

NXcg_grid, NXdata

Structure:

depends_on: (optional) NX_CHAR

Reference to an :ref:`NXcoordinate_system` in which the projection_direction i ...

Reference to an NXcoordinate_system in which the projection_direction is defined.

If the field depends_on is not provided but parents of the instance of this base class or its specializations define an instance of NXcoordinate_system, projection_direction is defined in this coordinate system.

If nothing is provided it is assumed that projection_direction is defined in the McStas coordinate system.

projection_direction: (optional) NX_NUMBER (Rank: 1, Dimensions: [3]) {units=NX_UNITLESS}

The direction along which orientations are projected.

interpolation: (optional) NX_CHAR

How where orientation values at positions of input_grid computed to values on ...

How where orientation values at positions of input_grid computed to values on output_grid.

Nearest neighbour means the orientation of the closed (Euclidean distance) grid point of the input_grid was taken.

Obligatory value: nearest_neighbour

input_grid: (optional) NXcg_grid

Details about the original grid. ...

Details about the original grid.

Here original grid means the grid for which the IPF map was computed when that IPF map was exported from the tech partner’s file format representation.

output_grid: (optional) NXcg_grid

Details about the grid onto which the IPF is recomputed. ...

Details about the grid onto which the IPF is recomputed.

Rescaling the visualization of the IPF map may be needed to enable visualization in specific software tools like H5Web.

map: (optional) NXdata

Inverse pole figure mapping. ...

Inverse pole figure mapping.

phase. No ipf_mapID instances for non-indexed scan points as these are by definition assigned the null phase with phase_identifier 0. Inspect the definition of NXcrystal_structure and its field phase_identifier for further details.

Details about possible regridding and associated interpolation during the computation of the IPF map visualization can be stored using the input_grid, output_grid, and interpolation fields.

The main purpose of this map is to offer a normalized default representation of the IPF map for consumption by a research data management system (RDMS). This is aligned with the first aim of NXmicrostructure_ipf, to bring colleagues and users of IPF maps together to discuss which pieces of information need storage.

We are convinced a step-by-step design and community-driven discussion is a practical strategy to work towards an interoperable description and data model for exchanging IPF maps as a specific community-accepted method to convey orientation maps.

With this design the individual RDMS solutions and tools can still continue to support specific custom data analyses workflow and routes but at least there is one common understanding which enables also those users who are not necessarily experts in all the details of the underlying techniques an understanding if the dataset is worth to become reused or repurposed.

data: (optional) NX_NUMBER (Rank: 3, Dimensions: [n_y, n_x, 3]) {units=NX_UNITLESS} ⤆

Inverse pole figure color code for each map coordinate.

axis_z: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_z]) {units=NX_LENGTH} ⤆

Pixel center coordinate calibrated for step size along the z axis of the map.

axis_y: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_y]) {units=NX_LENGTH} ⤆

Pixel center coordinate calibrated for step size along the y axis of the map.

axis_x: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_x]) {units=NX_LENGTH} ⤆

Pixel center coordinate calibrated for step size along the x axis of the map.

legend: (optional) NXdata

The color code which maps colors to orientation in the fundamental zone. ...

The color code which maps colors to orientation in the fundamental zone.

For each stereographic standard triangle (SST), i.e. a rendering of the fundamental zone of the crystal-symmetry-reduced orientation space SO3, it is possible to define a color model which assigns a color to each point in the fundamental zone.

Different mapping models are used. These implement (slightly) different scaling relations. Differences exist across representations of tech partners.

Differences are which base colors of the RGB color model are placed in which extremal position of the SST and where the white point is located.

For further details see:

Details are implementation-specific and not standardized yet.

Given that the SST has a complicated geometry, it can not yet be visualized using tools like H5Web, which is why for now the matrix of a rasterized image which is rendered by the backend tool gets copied into an RGB matrix to offer a default plot.

data: (optional) NX_NUMBER (Rank: 3, Dimensions: [n_y, n_x, 3]) {units=NX_UNITLESS} ⤆

Inverse pole figure color code for each map coordinate.

axis_y: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_y]) {units=NX_UNITLESS} ⤆

Pixel along the y-axis.

axis_x: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_x]) {units=NX_UNITLESS} ⤆

Pixel along the x-axis.

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

NXDL Source:

https://github.com/FAIRmat-NFDI/nexus_definitions/tree/fairmat/contributed_definitions/NXmicrostructure_ipf.nxdl.xml