# A dull and shadowed ‘rgl’ mesh

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The visualization of a **rgl** mesh is rather shiny by
default. We’ll see how to make it dull and shadowed.

Take for instance the Barth sextic:

## Barth sextic is the isosurface f=0 #### phi <- (1 + sqrt(5)) / 2 f <- function(x, y, z){ 4 * (phi^2*x^2 - y^2) * (phi^2*y^2 - z^2) * (phi^2*z^2 - x^2) - (1 + 2*phi) * (x^2 + y^2 + z^2 - 1)^2 } ## make the isosurface #### nx <- ny <- nz <- 250L x <- seq(-1.8, 1.8, length.out = nx) y <- seq(-1.8, 1.8, length.out = ny) z <- seq(-1.8, 1.8, length.out = nz) Grid <- expand.grid(X = x, Y = y, Z = z) voxel <- array(with(Grid, f(X, Y, Z)), dim = c(nx, ny, nz)) # we want to clip the mesh to the ball of radius √3, so we # assign a negative value to the voxel points outside this ball mask <- array(with(Grid, X^2 + Y^2 + Z^2 > 3), dim = c(nx, ny, nz)) voxel[mask] <- -1 # run the marching cubes library(rmarchingcubes) cont <- contour3d(voxel, level = 0, x = x, y = y, z = z) ## plot #### library(rgl) mesh <- tmesh3d( vertices = t(cont[["vertices"]]), indices = t(cont[["triangles"]]), normals = cont[["normals"]] ) # open3d(windowRect = 50 + c(0, 0, 512, 512)) bg3d("#363940") view3d(20, 45, zoom = 0.6) shade3d(mesh, color = "#ff00ff")

It is shiny. That’s because of the default lighting used by
**rgl**. To get a dull and shadowed mesh, one has first to
destroy these lights, and then to include our own light(s):

open3d(windowRect = 50 + c(0, 0, 512, 512)) bg3d("#363940") view3d(20, 45, zoom = 0.6) clear3d(type = "lights") # destroy current lights light3d(x = -50, y = 100, z = 100, ambient = "black") shade3d(mesh, color = "#ff00ff", specular = "black")

I also use a black specular light, it corresponds to the color for the shadows.

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