如何用rayshader的plot_gg()自定义或缩小3D图比例尺三角图例高度

使用rayshader包的plot_gg()函数渲染3D地图时，增大scale参数（如scale = 300）后，比例尺图例栏会部分遮挡图表，如何自定义或缩小该图例栏的高度？

用户代码示例：

gg_mai = ggplot(mai_sff) +
  geom_sf(aes(fill = songuoi_km), lwd=0) +
  scale_fill_viridis("Mật độ người/km2", direction = -1, option = "viridis") +
  ggtitle("Họ Mai") +
  theme_bw()

plot_gg(gg_mai, multicore = TRUE, raytrace = TRUE, width = 7, height = 4, 
       scale = 300, windowsize = c(1400, 866), zoom = 0.6, phi = 30, theta = 30)

方法1：在ggplot层面调整图例尺寸 #

通过theme()中的legend.key.height参数直接缩小图例高度，3D渲染时会沿用这个设置：

gg_mai = ggplot(mai_sff) +
  geom_sf(aes(fill = songuoi_km), lwd=0) +
  scale_fill_viridis("Mật độ người/km2", direction = -1, option = "viridis") +
  ggtitle("Họ Mai") +
  theme_bw() +
  theme(legend.key.height = unit(0.8, "cm"))  # 按需调整数值控制高度

plot_gg(gg_mai, multicore = TRUE, raytrace = TRUE, width = 7, height = 4, 
       scale = 300, windowsize = c(1400, 866), zoom = 0.6, phi = 30, theta = 30)

方法2：使用plot_gg的legend_height参数 #

plot_gg()内置了legend_height参数，可直接指定图例占图表高度的比例（范围0-1），比如设置为0.2：

plot_gg(gg_mai, multicore = TRUE, raytrace = TRUE, width = 7, height = 4, 
       scale = 300, windowsize = c(1400, 866), zoom = 0.6, phi = 30, theta = 30,
       legend_height = 0.2)  # 调整比例缩小图例

方法3：手动添加自定义图例（精细控制） #

先隐藏ggplot的图例，再用add_legend()手动添加，自定义位置、高度和宽度：

# 隐藏ggplot中的图例
gg_mai = ggplot(mai_sff) +
  geom_sf(aes(fill = songuoi_km), lwd=0) +
  scale_fill_viridis("Mật độ người/km2", direction = -1, option = "viridis") +
  ggtitle("Họ Mai") +
  theme_bw() +
  theme(legend.position = "none")

# 渲染3D图后添加自定义图例
plot_gg(gg_mai, multicore = TRUE, raytrace = TRUE, width = 7, height = 4, 
       scale = 300, windowsize = c(1400, 866), zoom = 0.6, phi = 30, theta = 30)
add_legend(position = "right", height = 100, width = 20)  # 按需调整尺寸

内容的提问来源于stack exchange，提问作者Duc Du