Gaussian Filter

Gaussian Filter smooths volume data by convoluting it with a 3D Gaussian function of user-specified width. This improves the ratio of signal to noise but reduces resolution.

There are several ways to start Gaussian Filter, a tool in the Volume Data category (including from the Volume Viewer Tools menu). The filtering applies to the current set of data in Volume Viewer.

Gaussian width (= 2 sdev) [width] - width of the 3D isotropic Gaussian function (width = 2σ)
Displayed subregion only - whether to limit the procedure to the current display region (which could be a subregion of the current set)
Displayed subsampling only - whether to use only the displayed subsample (when step > 1) instead of the full resolution of the current set

Clicking Filter or entering a width and pressing return (Enter) performs the convolution, which creates a new volume data set and makes it the current set; the original data set is hidden. The new data set can be saved to a file with Volume Viewer.

The filtering is fastest for data sizes that are powers of 2, and can be very slow when insufficient memory is available. It uses temporary memory four times the size of the input data (if in 32-bit floating point values) and produces a 32-bit floating point result. The subregion and subsampling options are useful for limiting the input data size.

Close dismisses the Gaussian Filter dialog; Help opens this manual page in a browser window.

UCSF Computer Graphics Laboratory / December 2007