shell.palette: Compute the colors and alpha values of the shells.

In fsbrain: Managing and Visualizing Brain Surface Data

Compute the colors and alpha values of the shells.

Description

The palette defines how the shells look: their colors and how transparent they are, from the outermost to the innermost shell. Three palettes are available:

• 'grey_context' (the default): all shells but the innermost one are grey (like the semi-transparent cortex in vis.subcortical.region.values is), and the innermost shell is rendered in a warm color and fully opaque. This gives the impression of looking at a structure inside a translucent head, and it makes a single feature stand out, at the price of hiding the level of the inner shells.

• 'sequential': a single hue, getting lighter and more opaque towards the innermost shell. Useful to emphasize the nested structure, and to avoid the colorful look of 'viridis'.

• 'viridis': the full viridis ramp, with the outer shells dark and very transparent and the inner ones bright. This is the most colorful option, and it encodes the iso-level in the color.

Usage

shell.palette(palette = "grey_context", num_shells = 4L, alpha_range = NULL)

Arguments

palette	character string, the name of the palette: one of 'grey_context', 'sequential' or 'viridis'.
num_shells	positive integer, the number of shells.
alpha_range	numerical vector of length 2 or NULL. The alpha value of the outermost and of the innermost (non-opaque) shell. If NULL, the default range of the palette is used.

Value

a named list with the entries 'colors' (character vector, one color per shell) and 'alphas' (numerical vector, one alpha value per shell).

fsbrain documentation built on Sept. 27, 2026, 1:07 a.m.