Lattice 3d coordinate transformation

require(lattice)
..."

Hello List!
I asked this before (with no solution), but maybe this time... I'm
trying to project a surface to the XY under a 3d cloud using lattice.
I can project contour lines following the code for fig 13.7 in
Deepayan Sarkar's "Lattice, Multivariate Data Visualization with R",
but it fails when I try to "color them in" using panel.levelplot.
?utilities.3d says there may be some bugs, and I think
ltransform3dto3d() is not precise (where did I hear that?), but is
this really the source of my problem? Is there a (simple?) workaround,
maybe using 3d.wire but projecting it to XY? How? Please, any insight
may be useful.
Thanks in advance,
Elai.

A working example:

?## data "d" and predicted "surf":
set.seed(1113)
d <- data.frame(x=runif(30),y=runif(30),g=gl(2,15))
d$z <- with(d,rnorm(30,3*asin(x^2)-5*y^as.integer(g),.1))
d$z <- d$z+min(d$z)^2
surf <- by(d,d$g,function(D){
?fit <- lm(z~poly(x,2)*poly(y,2),data=D)
?outer(seq(0,1,l=10),seq(0,1,l=10),function(x,y,...)
predict(fit,data.frame(x=x,y=y)))
})
##
# This works to get contours:
require(lattice)
cloud(z~x+y|g,data=d,layout=c(2,1), type='h', lwd=3, par.box=list(lty=0),
? ? ?scales=list(z=list(arrows=F,tck=0)),
? ? ?panel.3d.cloud = function(x, y, z,rot.mat, distance,
zlim.scaled, nlevels=20,...){
? ? ? ?add.line <- trellis.par.get("add.line")
? ? ? ?clines <- contourLines(surf[[packet.number()]],nlevels = nlevels)
? ? ? ?for (ll in clines) {
? ? ? ? ?m <- ltransform3dto3d(rbind(ll$x-.5, ll$y-.5,
zlim.scaled[1]), rot.mat,
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?distance)
? ? ? ? ?panel.lines(m[1,], m[2,], col = add.line$col, lty = add.line$lty,
? ? ? ? ? ? ? ? ? ? ?lwd = add.line$lwd)
? ? ? ?}
? ? ? ?panel.3dscatter(x, y, z, rot.mat, distance, zlim.scaled =
zlim.scaled, ...)
? ? ?}
? ? ?)
# But using levelplot:
panel.3d.levels <- function(x, y, z,rot.mat, distance, zlim.scaled,...)
{
? ?zz <- surf[[packet.number()]]
? ?n <- nrow(zz)
? ?s <- seq(-.5,.5,l=n)
? ?m <- ltransform3dto3d(rbind(rep(s,n),rep(s,each=n),zlim.scaled[1]),
? ? ? ? ? ? ? ? ? ? ? ? ?rot.mat, distance)
? ?panel.levelplot(m[1,],m[2,],zz,1:n^2,col.regions=heat.colors(20))
? ?panel.3dscatter(x, y, z, rot.mat, distance, zlim.scaled = zlim.scaled, ...)
?}
cloud(z~x+y|g,data=d,layout=c(2,1), type='h', panel.3d.cloud = panel.3d.levels,
? ? ?scales=list(z=list(arrows=F,tck=0)),par.box=list(lty=0),lwd=3)
# I also tried to "fill" between contours but can't figure out what to
do with the edges and how to incorporate the x,y limits to 1st and nth
levels.
panel.3d.contour <- function(x, y, z,rot.mat, distance,xlim,ylim,
zlim.scaled,nlevels=20,...)
{
? ?add.line <- trellis.par.get("add.line")
? ?zz <- surf[[packet.number()]]
? ?clines <- contourLines(zz,nlevels = nlevels)
? ?colreg <- heat.colors(max(unlist(lapply(clines,function(ll) ll$level))))
? ?for (i in 2:length(clines)) {
? ? ?ll <- clines[[i]]
? ? ?ll0 <- clines[[i-1]]
? ? ?m <- ltransform3dto3d(rbind(ll$x-.5, ll$y-.5, zlim.scaled[1]),
rot.mat, distance)
? ? ?m0 <- ltransform3dto3d(rbind(ll0$x-.5, ll0$y-.5,
zlim.scaled[1]), rot.mat, distance)
? ? ?xvec <- c(m0[1,],m[1,ncol(m):1])
? ? ?yvec <- c(m0[2,],m[2,ncol(m):1])
? ? ?panel.polygon(xvec,yvec,col=colreg[ll$level],border='transparent')
? ? ?panel.lines(m[1,], m[2,], col = add.line$col, lty = add.line$lty,
? ? ? ? ? ? ? ? ?lwd = add.line$lwd)
? ?}
? ?panel.3dscatter(x, y, z, rot.mat, distance, zlim.scaled = zlim.scaled, ...)
?}
cloud(z~x+y|g,data=d,layout=c(2,1), type='h', panel.3d.cloud = panel.3d.contour,
? ? ?scales=list(z=list(arrows=F,tck=0)),par.box=list(lty=0),lwd=3)

#############################################################################