SY DOC - Create Symmetry Document file

PURPOSE

Creates a document file containing symmetry Euler angles. Creates angles for following symmetry groups:
(C)yclic group, with only one axis of rotational symetry
(CI)Cyclic group w/ inversion, or dihedral groups
(T)etrahedral group, where ref. structure is 4-sided polygon
(O)ctohedral group, that is also holohedral, effectively a cube
(I)cosahedral group, regular 20-sided closed polygon.

SEE ALSO

RT 3	[RoTate - volume, slow]
RT SQ	[Rotate and Shift - image, Quadratic interpolation ||]
AP SH	[Alignment - multi-reference, exhaustive rotation & shift ||*]
AP REF	[Alignment - multi-reference, rotation & shift ||*]

USAGE

.OPERATION: SY

.OUTPUT SYMMETRY DOCUMENT FILE: DOC002
[Enter name of output document file.]

.SYMMETRY TYPE (C / CI / T / O / I): C
[Enter symmetry type.]

If the symmetry type was 'C' or 'CI' the following question will appear.

.SYMMETRY FOLDNESS: 5
[ Enter rotational symmetry parameter. ]

NOTES

1. Assumes right-handed coordinate system, and rotations as described for SPIDER's Euler angles.
   

2. Objects with rotational symmetry (types: 'C' and Ci') should be oriented with rotational axis parallel with the Z axis and centered within the volume.

3. Objects with tetrahedral symmetry should be oriented with the 3-fold rotational axis parallel with the Z axis, with a vertex on the positive Z axis. Also, a vertex should be along the positive X axis.
   

4. Objects with symmetry Icosahedral symmetry should be oriented with The he axis of 5-fold rotational symmetry along the Z axis. When the structure is viewed from the positve Z axis, one edge should point along the positive X axis.

5. Objects with Octo/holo-hedral(cubic) symmetry should be oriented with so that each axis is normal to a face of the cube.
   

6. Useful discussions of the use of Euler angles to rotate 3D bodies can be found at mathworld and here. Please note that these websites do not necessarily use the same conventions as SPIDER does, but this does.

7. Implemented by Jamie Lebarron.

SUBROUTINES

SYMANG

CALLER

DRIV3