`light.Rd`

add a light source to the scene.

```
light3d(theta = 0, phi = 15, x = NULL, ...)
rgl.light( theta = 0, phi = 0, viewpoint.rel = TRUE, ambient = "#FFFFFF",
diffuse = "#FFFFFF", specular = "#FFFFFF", x = NULL, y = NULL, z = NULL)
```

- theta, phi
polar coordinates, used by default

- viewpoint.rel
logical, if TRUE light is a viewpoint light that is positioned relative to the current viewpoint

- ambient, diffuse, specular
light color values used for lighting calculation

- x, y, z
cartesian coordinates, optional

- ...
generic arguments passed through to RGL-specific (or other) functions

Up to 8 light sources are supported. They are positioned either in world space or relative to the camera. By providing polar coordinates to theta and phi a directional light source is used. If numerical values are given to x, y and z, a point-like light source with finite distance to the objects in the scene is set up.

If `x`

is non-null, `xyz.coords`

will
be used to form the location values, so all three coordinates
can be specified in `x`

.

If no lights have been added to a subscene, lights from the parent subscene will be used.

See `material3d`

for a discussion of how
the components of the light affect the display of objects.

This function is called for the side effect of adding a light. A light ID is
returned to allow `pop3d`

to remove it.

```
#
# a lightsource moving through the scene
#
data(volcano)
z <- 2 * volcano # Exaggerate the relief
x <- 10 * (1:nrow(z)) # 10 meter spacing (S to N)
y <- 10 * (1:ncol(z)) # 10 meter spacing (E to W)
zlim <- range(z)
zlen <- zlim[2] - zlim[1] + 1
colorlut <- terrain.colors(zlen) # height color lookup table
col <- colorlut[ z - zlim[1] + 1 ] # assign colors to heights for each point
open3d()
bg3d("gray50")
surface3d(x, y, z, color = col, back = "lines")
r <- max(y) - mean(y)
lightid <- spheres3d(1, 1, 1, alpha = 0)
frame <- function(time) {
a <- pi*(time - 1)
save <- par3d(skipRedraw = TRUE)
clear3d(type = "lights")
pop3d(id = lightid)
xyz <- matrix(c(r*sin(a) + mean(x), r*cos(a) + mean(y), max(z)), ncol = 3)
light3d(x = xyz, diffuse = "gray75",
specular = "gray75", viewpoint.rel = FALSE)
light3d(diffuse = "gray10", specular = "gray25")
lightid <<- spheres3d(xyz, emission = "white", radius = 4)
par3d(save)
Sys.sleep(0.02)
NULL
}
play3d(frame, duration = 2)
```