Enhanced rectangle element with alpha support

This function extends ggplot2::element_rect() to support transparency via an alpha parameter, which is attached to the returned element as an R attribute ("ggcube_alpha"). The attribute survives ggplot2's theme inheritance machinery, so the alpha value set here is available to the renderer at draw time. The alpha parameter is consumed only by coord_3d()'s panel rendering and has no effect on other theme elements.

Usage

element_rect(fill = NULL, alpha = NA, ...)

Arguments

fill

Fill colour for the rectangle.

alpha

Transparency level applied to the fill of foreground or background panels in coord_3d(), ranging from 0 (completely transparent) to 1 (completely opaque). For panel.foreground, the alpha resolves in order: an explicit value here, then alpha inherited from panel.background, then a default of 0.2. For panel.background, an explicit value is used directly; otherwise the panel is fully opaque. Has no effect on other theme elements or in plots without a 3D coordinate system.

...

Additional arguments passed to element_rect, such as colour, linewidth, linetype, and inherit.blank.

Value

A ggplot2::element_rect theme element with an attached "ggcube_alpha" attribute.

See also

element_rect for the original function, coord_3d for 3D coordinate systems that utilize foreground panels

Examples

# Basic 3D plot with semi-transparent foreground panels
ggplot(mountain, aes(x, y, z)) +
  stat_surface_3d(fill = "darkblue", color = "lightblue", linewidth = .1) +
  coord_3d(panels = c("background", "ymin")) +
  theme(panel.foreground = element_rect(alpha = 0.6))


# Completely transparent foreground panels
ggplot(mtcars, aes(mpg, wt, qsec)) +
  geom_point() +
  coord_3d(panels = "all") +
  theme(panel.border = element_rect(color = "black"),
        panel.foreground = element_rect(fill = "blue", alpha = 0))