Spanner 3D Display Example

Spanner 3D Display Example

This example script demonstrates the process of reading a LAS file and visualizing it in 3D using the lidR, spanner, and plotly libraries in R.

Import Libraries

library(lidR)
library(spanner)
library(plotly)

Load and Filter LAS File

The following code reads a LAS file, applies a filter to drop points below a certain height, and extracts a region of interest (ROI).

# Replace 'path_to_las_file' with the actual path to your LAS file
LASfile <- system.file("extdata", "MixedConifer.laz", package="lidR")
poi <- "-drop_z_below 0 -inside 481280 3812940 481320 3812980"
las <- readLAS(LASfile, select = "xyz", filter = poi)

# Check if LAS data is read correctly
if (is.null(las)) {
  stop("Failed to read LAS file")
}

Tree Segmentation

This section segments trees in the LAS file using the Li et al. (2012) algorithm.

las <- segment_trees(las, li2012(dt1 = 1.4))

Custom Color Palette

The custom function spanner_pal creates a continuous color palette for visualization purposes.

spanner_pal <- function(n) {
  colors <- c(
    "#F52220", "#E8801A", "#E1DA8A", "#5EA530", "#114232",
    "#2BB4A2", "#115A5D", "#B20F66", "#560F11", "#C0181A"
  )
  colorRampPalette(colors)(n)
}

3D Visualization of LAS Data

This function displays the LAS data in 3D using the plotly library.

display_las_3d <- function(las, point_size = 3) {
  # Check if the LAS object is valid
  if (is.null(las) || !inherits(las, "LAS")) {
    stop("Invalid LAS object")
  }

  # Extract the coordinates and treeID
  coords <- as.data.frame(las@data[, c("X", "Y", "Z", "treeID")])

  # Create a 3D scatter plot
  plot_ly(coords, x = ~X, y = ~Y, z = ~Z, color = ~treeID, 
          colors = spanner_pal(length(unique(coords$treeID))), 
          type = "scatter3d", mode = "markers", marker = list(size = point_size)) %>%
    layout(scene = list(xaxis = list(title = 'X'),
                        yaxis = list(title = 'Y'),
                        zaxis = list(title = 'Z')))
}

Example Usage

# Display the LAS data in 3D
display_las_3d(las)

The above code will create an interactive 3D scatter plot of the LAS data, colored by treeID, allowing you to explore the point cloud in a 3D space.