3D interactive surface plot with spatial data

Question

I would like to create an interactive 3D surface plot of depths in a lake, ideally using the plotly or rgl libraries. I have extracted my data from a SpatialLinesDataFrame of contour lines in Gauss-Krueger/EPSG:31468 CRS, i.e. metric units. Now each contour line produces a set of coordinates with the same depth value. The resulting data frame is rather large, but looks something like this:

set.seed(41)
xx <- rnorm(100,4448929,100)
yy <- rnorm(100,5308097,100)
zz <- c(rep(-10,10),rep(-20,10),rep(-30,10),rep(-40,10),rep(-50,10),rep(-60,10),rep(-70,10),rep(-80,10),rep(-90,10),rep(-100,10))
df <- data.frame(xx,yy,zz)

I have tried plotting the data with plotly as in this example and with rgl as in this post. In both cases I get error messages relating to my data not being in a matrix format, i.e. where x- and y-values are represented as row- and column-numbers.

What does work, is using the add_trace command in plotly:

plot_ly() %>% add_trace(df,x = ~df$xx, y = ~df$yy, z = ~df$zz,type="mesh3d")

However, the resulting graph not only lacks the fancy colour legend of the add_surface command, but more importantly, warps the x- and y-values in relation to the z-values. The z-values are shown much too large, although all have the same metric unit.

I have also tried reshaping the data frame to a matrix as in this post, but it either doesn't work at all, or gives me a matrix consisting almost entirely of NAs. I can only speculate that the number of coordinates that have depth values attached is very small in comparison to all x-y-combinations of coordinates in that range?

Any suggestions will be much appreciated - thanks!

Answer 1

Those are randomly located points, so rgl::persp3d can't handle them directly. However, you can follow the example in ?rgl::persp3d.deldir to triangulate them and then plot. For example,

dxyz <- deldir::deldir(df$xx, df$yy, z = df$zz, suppressMsgs=TRUE)
persp3d(dxyz, col = "lightblue")

This results in a pretty ugly picture, but with some work (e.g. fixing the axis labels, using real data) you should get something reasonable.