[cctbxbb] structure factor interpolation

[Ralf W. Grosse-Kunstleve]

Hi Jon,



> Perhaps I have misunderstoond the question.... Isn't it equivalent for 
> the unit cell to be expanded in real space so that the lattice points 
> are compressed in reciprocal space? Just expand the structure to P1 and 
> keep the atoms fixed in real space orthogonal angstrom co-ordinates. 
> Like this it seems you can get the reciprocal space points whereever you 
> want?

I think that's correct, but you need to decide how big to make the
pseudo unit cell, and how to interpolate. I looked at the phaser code,
where they have simple two-point interpolation, four-point and eight-point.

We have cctbx.crystal.non_crystallographic_symmetry(), which uses
cctbx.uctbx.non_crystallographic_unit_cell() to do the actual work, and
cctbx.uctbx.non_crystallographic_unit_cell_with_the_sites_in_its_center()
which moves the coordinates around.

And we have cctbx.maptbx.non_crystallographic_eight_point_interpolation,
implemented in cctbx/maptbx/eight_point_interpolation.h .

Hope this helps.

Ralf