** Next:** Acknowledgements
**Up:** The Stereographic Projection
** Previous:** 6. Calculations Based on the Stereogram

Any problem involving only directions in space can be reduced to a problem relating to a distribution of points on a sphere, and can therefore be represented in a stereogram. The symmetry relationships between the components of a twin (or of a more complex intergrowth of more than two individual crystals) can obviously be represented in this way. For partially orientated polycrystalline aggregates (e.g. rolled metal sheets, stretched polymers, rock textures) the orientations in space of the normal to some particular crystallographic plane can be plotted on the stereogram, and contours can be drawn to indicate the range of orientations involved. Such diagrams are known as pole figures.

**Copyright © 1984, 1997 International Union of
Crystallography**