meshroom

The goal of meshroom is to provide the heightmap meshing facility of the hmm library to R.

It currently returns a matrix of XYZ coordinates - every three rows is a triangle. We can also set file_stl to write to STL if needed.

WARNING: the orientation of the input and output is not assured at the moment and will change.

TODO

• DONE: STL output
• DONE: allow input from in memory matrix
• DONE (see below): maintain mapping for geospatial coordinates
• DONE auto-rescale input to full greyscale range
• DONE capture output triangles
• maintain real world z values
• sort out use of hmm, see notes below and in 00_meshroom.cpp
• support Windows
• support MacOS

Installation

Only on Linux.

sudo apt-get install libglm-dev

remotes::install_github("hypertidy/meshroom")

Example

library(meshroom)
#f <- system.file("extdata/volcano1.png", package = "meshroom", mustWork = TRUE)

m <- meshroom::hmm_triangles(volcano)
#>   error = 5.96046e-08
#>   points = 3479
#>   triangles = 6795
#>   vs. naive = 65.843%


m50 <- meshroom::hmm_triangles(volcano, max_triangles = 50)
#>   error = 0.161089
#>   points = 29
#>   triangles = 51
#>   vs. naive = 0.494186%

Compare different numbers of triangles from volcano.

plot(m50, type = "n", asp = 1)
ii <- rbind(matrix(seq_len(nrow(m50)), nrow = 3), NA)
polygon(m50[ii, ])

m500 <- meshroom::hmm_triangles(volcano, max_triangles = 500)
#>   error = 0.029703
#>   points = 260
#>   triangles = 501
#>   vs. naive = 4.85465%

plot(m500, type = "n", asp = 1)
ii <- rbind(matrix(seq_len(nrow(m500)), nrow = 3), NA)
polygon(m500[ii, ])

Now write to STL if needed check it out.

meshroom::hmm_triangles(volcano, z_exaggeration = 30, stl_file = "man/figures/volcano2.stl")

notes

## https://github.com/fogleman/hmm
f <- fs::dir_ls("../hmm/src")
fs::file_copy(f, "./src/", overwrite = TRUE)
fs::file_copy("../hmm/LICENSE.md", "src/")
tools::package_native_routine_registration_skeleton("../meshroom", "src/init.c",character_only = FALSE)

## local testing
library(raster)
d <- raadtools::readtopo("etopo2", xylim = raster::extent(100, 180, -70, -30))
d <- aggregate(d, fact = 8)

unlink("stl.stl"); meshroom:::hmm_triangles(as.matrix(d),  stl_file = "stl.stl", invert = T)
rgl::rgl.clear(); r <- rgl::readSTL("stl.stl", plot = TRUE, col = "grey", lit = TRUE); rgl::aspect3d(1, 1, .2); rgl::rglwidget()

Example of restoring geospatial information.

library(ceramic)
ex <- raster::extent(144, 149, -44, -40)
el <- cc_elevation(ex, zoom = 5)
el[el < 1] <- NA
tris <- meshroom:::hmm_triangles(as.matrix(el),   z_scale = TRUE)

## now re-map geographic coordinates back int
library(raster)
cell <- cellFromXY(setExtent(el, raster::extent(1, ncol(el), 1, nrow(el))), 
                   tris[,1:2] + 1)


tris[,1:2] <- xyFromCell(el, cell)

## and unproject just for fun
tris[,1:2] <- rgdal::project(tris[,1:2], projection(el), inv = TRUE)
rgl::rgl.clear(); rgl::triangles3d(tris[,1], tris[,2], tris[,3], 
                                   col = rep(c("white", "grey", "black", "darkgrey"), each = 3));
rgl::aspect3d(1, 1, .035); rgl::rglwidget()
rgl::par3d()$bbox

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Please note that the ‘meshroom’ project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.