R rgl lidR slow rendering on Windows 11 64 bit

Question

I am trying to manually identify/correct trees using LiDAR data (1.7 GB object) and a tree tops object via the locate_trees function. Part of the problem is:

1. Rgl is rendering very slow even though the 4 GB Nvidia 3050 should be able to handle it.
2. The tree tops (red 3D dots) are not even showing in the rgl window. When I close the rgl window, the tree tops start popping up (red dots appear and disappear resulting in a blank white window) in a new rgl window. And if I close that window, a new tree top window opens up so I stop the process to prevent this from happening.

Does rgl automatically use the GPU or does it default to the integrated graphics on the motherboard? Is there a way to fasten up the rendering?

My other system specs are Corei9 (14 threads) and 64 GB RAM. Moreover, I am using R 4.2.1.

Code:

library(lidR)

# Import LiDAR data
LiDAR_File = readLAS("path/file_name.las")

# Find tree tops
TTops = find_trees(LiDAR_File , lmf(ws = 15, hmin = 5))

# Manually correct tree identification
TTops_Manual = locate_trees(LiDAR_File , manual(TTops)) # This is where rgl rendering becomes too slow if there are too many points involved. 

Answer 1

There were two problems here. First, the lidR::manual() function which is used to select trees has a loop where one sphere is drawn for each tree. By default rgl will redraw the whole scene after each change; this should be suppressed. The patch in https://github.com/r-lidar/lidR/pull/611 fixes this. You can install a version with this fix as

remotes::install_github("r-lidar/lidR")

Second, rgl was somewhat inefficient in drawing the initial point cloud of data, duplicating the data unnecessarily. When you have tens of millions of points, this can exhaust all R memory, and things slow to a crawl. The development version of rgl fixes this. It's available via

remotes::install_github("dmurdoch/rgl")

The LiDAR images are very big, so you might find you still have problems even with these changes. Getting more regular RAM will help R: you may need this if the time to the first display is too long. After the first display, almost all the work is done in the graphics system; if things are still too slow, you may need a faster graphics card (or more memory for it).