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\name{image3d}
\alias{image3d}
\title{Draw Points on a 3D Grid}
\description{
Plots points on a three dimensional grid representing values in a
three dimensional array. Assumes high values are inside and uses alpha
blending to make outside points more transparent.
}
\usage{
image3d(v, x = 1:dim(v)[1], y = 1:dim(v)[2], z = 1:dim(v)[3],
vlim = quantile(v, c(.9, 1),na.rm=TRUE),
col = heat.colors(256), alpha.power = 2,
alpha = ((1:length(col))/ length(col))^alpha.power,
breaks, sprites = TRUE, jitter = FALSE,
radius = min(diff(x), diff(y), diff(z)),
add = FALSE,...)
}
\arguments{
\item{v}{three dimensional data array.}
\item{x,y,z}{locations of grid planes at which values in \code{v} are
measured.}
\item{vlim}{minimum and maximum \code{v} values for which points are
to be drawn.}
\item{col}{vector of colors for the points as generated by
\code{heat.colors} or similar functions.}
\item{alpha.power}{used to calculate the alpha values. The larger the
power, the smaller the alpha, the more transparent the point. Only
used if \code{alpha} is not supplied.}
\item{alpha}{vector of alpha values between 0 and 1. The length of
the vector should be equal to the length of \code{col}.}
\item{breaks}{breakpoints for the colors; must give one more
breakpoint than colors.}
\item{sprites}{logical; if \code{TRUE}, use \code{rgl.sprites} to
draw the points.}
\item{radius}{radius used in \code{rgl.sprites}.}
\item{jitter}{logical; if \code{TRUE}, add a small amount of noise to
the point locations.}
\item{add}{logical; if \code{TRUE}, add to current \code{rgl} graph.}
\item{...}{material and texture properties. See \code{rgl.material}
for details.}
}
\references{
Daniel Adler, Oleg Nenadic and Walter Zucchini (2003)
RGL: A R-library for 3D visualization with OpenGL
}
\seealso{
\code{\link{image}}, \code{\link[rgl]{rgl.sprites}},
\code{\link[rgl]{rgl.points}}, \code{\link{jitter}}.
}
\examples{
# view density of mixture of tri-variate normals
nmix3 <- function(x, y, z, m, s) {
0.4 * dnorm(x, m, s) * dnorm(y, m, s) * dnorm(z, m, s) +
0.3 * dnorm(x, -m, s) * dnorm(y, -m, s) * dnorm(z, -m, s) +
0.3 * dnorm(x, m, s) * dnorm(y, -1.5 * m, s) * dnorm(z, m, s)
}
f <- function(x,y,z) nmix3(x,y,z,.5,.5)
x<-seq(-2,2,len=50)
g <- expand.grid(x = x, y = x, z = x)
v <- array(f(g$x, g$y, g$z), c(length(x), length(x), length(x)))
image3d(v)
image3d(v, jitter = TRUE)
}
\keyword{hplot}
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