To understand how a material evolves - its crystal growth, topotaxy, twinning, phase transformation, plastic deformation, microstress, etc. - it is important to know the crystal orientations, either between them or in respect to the sample.
The crystal texture of the material is quantified by the Orientation Distribution Function (O.D.F.). This function represents the part of the material volume having a given orientation. To compute this O.D.F, we must first measure one or several complete or incomplete pole figures and then analyse them either with Roe-Bunge's harmonic method or with Vadon, Ruer, Baro's vector method. In the case of a very sharp texture, the results obtained with the harmonic method are not good because developing a DIRAC function in spherical harmonics requires a high rank, hence a large number of pole figures. On the contrary, with the vector method, the results are good since discretizing amounts to developing on a step-function basis.