#
Gaussian Filter

February 27, 2007

This tool smooths volume data by performing a convolution with a Gaussian
of user-specified width. This improves signal to noise but reduces
resolution. It acts on the volume set currently displayed
in the volume viewer dialog. It produces a new volume data set that is
shown with volume viewer and hides the original data set.

##
User Interface Dialog

Use menu entry

**
Tools / Volume Data / Gaussian Filter
**
to display the Gaussian Filter dialog.
Enter the width of the Gaussian defined as twice the standard deviation
and press the Filter button.

##
Speed

The computation is fastest for data sizes that are powers of 2.

For a data set of size 128^{3} the computation takes a few seconds
on a desktop computers circa 2006. A 256^{3} data set takes a few
tens of seconds. The computation for larger data sets can become very slow
if insufficient memory is available.

##
Memory Use

The code currently uses 4 times the memory of the input data set (if it
is 32-bit floating point values) as temporary working space and produces
a 32-bit floating point result. Temporary memory use would only be twice
the input data set except that the NumPy FFT package being used
always produces 64-bit float or complex results.

##
History

**February 27, 2007**.
Updated for Chimera version 1.2348 which uses NumPy instead of Numeric Python.

**October 10, 2006**.
Initial version.