Shapes render incorrectly with FOV=0

[dmurdoch]

This example renders incorrectly:

library(rgl)
open3d()
#> glX 
#>   1
z <- c(0,0,1)
y <- c(0,1,0)
x <- c(1,0,0)
corner1 <- c(1,1,2,2) # vector entry with corner of square
corner2 <- c(2,3,3,2) # other corner
bg3d(color = "white")
spheres3d(x, y, z, r = 0.2, color = "grey") 
quads3d(cbind(0, y[corner1], z[corner2]),
        col = "blue", alpha = 0.6)
quads3d(cbind(x[corner1], 0, z[corner2]), 
        col = 'red', alpha = 0.6)
quads3d(cbind(x[corner1], y[corner2], 0), 
        col = 'green', alpha = 0.6)
view3d(theta=230, phi=-30, zoom=1, fov=0)

^{Created on 2024-01-10 with reprex v2.0.2} In R, it is not too bad, but the highlights on the spheres are in the wrong place, as if the light was close to the shape, instead of infinitely distant. But the rglwidget() display is terrible, showing black edges to the spheres.

So far the only workaround I have is to use fov = 0.001 instead of fov = 0; this appears to render correctly.