-blur_xyz

This command is a specialization of the -blur command which permits one to independently set the standard variation along each of the x, y, and z axes. The -display of a 100,100,100,1 volumetric star field, depicted on the left, illustrates how different settings along each axis gives rise to elliptic blurs not possible with the standard command.

The format of the command is:

-blur_xyz amplitude_x[%], amplitude_y[%], amplitude_z, _boundary={ 0=dirichlet | 1=neumann }

• amplitude_x, aplitude_y, amplitude_z: sets the spread of the Gaussian distribution kernel, informally the amount of blurring, along the x, y, and z axes. One must supply a value for each parameter; there are no defaults. If you intend to set one or another amplitude to zero, consider using -blur_xy,  -blur_x,  -blur_y or -blur_z, as appropriate.
• _boundary: chooses how to handle image edges; see "Pictures have Edges. Now What?" A zero flag (0, Dirichlet) assumes that off-image pixels are black. A unit flag (1, Neumann) assumes that off-image pixels have the exact same value as the nearest edge pixel. Neumann does not exhibit a black vignette, but sometimes edge values become uncommonly bright. This value may be omitted and when it is, the command uses the Neumann policy as a default.

Garry Osgood