VO NEA - Vector Operation - Create More Uniformly Spaced Angles

(04/01/13)

PURPOSE

Creates doc file listing of three Eulerian angles quasi-evenly spaced on surface of a sphere. This document file can be used to calculate reference projections (operation 'PJ 3Q') for the 3D alignment 'AP SH' operation Alignment). Provides more 'uniform' coverage than 'VO EA'. Uses a logarithmic spiral for spacing the projections.   Example.

SEE ALSO

VO EA [Vector Operation - Create Doc File Containing Evenly Spaced Angles]
AP SH [Alignment - multi-reference, exhaustive rotation & shift ||*]
AP REF [Alignment - multi-reference, rotation & shift ||*]

USAGE

.OPERATION: VO NEA [NANG]

.NUMBER OF ANGLES: 83
[The number of angles desired.]

.HALF SPHERE (Y/N): Y
[Sets range of coverage. A full sphere gives 0<theta<180, but the projections with theta>90 are mirrored versions of projections with theta<90. This mirroring can be done implicitly in some 'AP' operation options which only require coverage over half of the spherical directions. If only a half sphere is wanted the number of projections may not be exactly what you have requested. In this case you can use an optional operation line register variable to retrieve the actual number of projections created.]

.ANGULAR DOCUMENT FILE: ANGFULL
[Enter the name of the output angular docfile. The file will contain the Eulerian angles psi, theta, phi as required by the 'AP SH' or 'AP REF' operations.]

NOTES

  1. This distribution may be difficult to adjust for symmetric structures. You may wish to use 'VO EA' instead.

  2. Implemented by A. Leith

SUBROUTINES

VONEA, PTS_ON_SPHERE

CALLER

DRIV1

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