Draws dark, low-opacity copies of a stroked or point mark beneath the
original, offset by (x, y) and softened by stacking a few widened copies —
a drop shadow (with an offset) or an ambient shadow (offset 0). Applies to
the same marks as glow().
Usage
shadow(
x = 0.5,
y = -0.5,
color = "black",
alpha = 0.3,
spread = 1.5,
layers = 3L
)
Arguments
- x, y
Shadow offset in millimetres (+x right, +y up). Defaults to a
small down-right drop.
- color
Shadow colour.
- alpha
Opacity of each copy.
- spread
Softening spread, in millimetres, over which the copies widen.
- layers
Number of stacked copies (more = softer).
Value
A ShadowSpec object for a mark's effects list.
Details
The offset is an absolute distance in millimetres (+x right, +y up),
resolved device-side, so a drop shadow stays the same physical distance and is
isotropic regardless of the panel's size or aspect (via vellum's compound
npc + mm unit).
