[Chimera-users] Laplacian filter on density maps

Tom Goddard goddard at cgl.ucsf.edu
Tue Nov 18 23:03:36 PST 2008

Hi Greg,

  A Laplacian filter is simple to implement.  I'll see if I can add it 
to the "vop" command later this week.  The Laplacian filter roughly 
speaking does edge detection so alignments of filtered maps will try to 
match the boundaries of the objects.  The Laplacian is a sum of second 
derivatives and will be useless on noisy data (e.g. any tomography) 
unless you smooth the data first with for instance a Gaussian filter.


Grigore Pintilie wrote:
> Hi,
> Just wondering if it might be possible to apply a Laplacian filter on
> a density map in chimera. The reason I'm asking is that if the
> cross-correlation is computed with laplacian-filtered maps it gives
> more robust results for the correct alignments vs. non-correct
> alignments.
> Thanks,
> Greg
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