VO EA - Vector Operation - Create Evenly Spaced Angles Document file

PURPOSE

Create angular document file containing three Eulerian angles defining quasi-evenly spaced projection directions. This document file can be used to create reference projections from a volume (using operation: 'PJ 3Q') for the 'AP SH' operation (3D Projection Alignment).

SEE ALSO

VO MD	[Vector Operation - angular Document file from 'AP MD' output]
VO RA	[Vector Operation - Rotate Angular document file]
VO IA	[Vector Operation - Find Included Angle]
AP SH	[Alignment - multi-reference, exhaustive rotation & shift ||*]
PJ 3Q	[Project - 3D volume using Eulerian angles ||]

USAGE

.OPERATION: VO EA [num-angles]

[[num-angles] is an optional register variable which will receive the number of angular directions for the angular step specified (see note 3).]

.DELTA THETA: 2.0
[The angular step for the theta angles. The angular step for the phi angle is adjusted according to the equation
d(phi) = d(theta)   /   sin(theta)
to create quasi-evenly spaced directions.]

.RANGE OF THETA (0,90): 0.0, 90.0
[Range of theta angle. Default is 0,90, as used by the 'AP SH' or 'AP REF' operations with CHECK MIRRORED POSITIONS?: 1]

.RANGE OF PHI (0,359.9): 0.0, 359.9
[Range of phi angle. Default is 0, 359.9, as used by the 'AP SH' or 'AP REF' operations with CHECK MIRRORED POSITIONS?: 1]

.ANGULAR DOCUMENT FILE NAME: 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. The default range of angles covers only half of the full angular range of directions. The full range would require 0<theta<180, but the projections with theta>90 are mirrored versions of projections with theta<90; this can be implicitly taken into account in the 'AP SH' or 'AP REF' operation.

2. For symmetric structures the ranges of angles must be adjusted properly (depending on the symmetry).

3. Numbers of directions for default angular range:

    
      Delta theta       Number of directions 
         15.0                84 
         10.0               195 
          5.0               799 
          2.5              3248 
          2.0              5088 
          1.5              9076 
          1.0             20489 
   

4. Implemented by P. Penczek

SUBROUTINES

VOEA

CALLER

DRIV1