Thanks Duncan!
yes! this works;
I paste the code in case someone wants to draw
3d-vectors with cylinders and cones.
René
vector3D=function(start=c(0,0,0), end, mycol='green', cone.length=0.1, ... ){
# ... cylinder as basis-vector
c=cylinder3d(rbind( c(start), # start
c(0,0,1)), # end
radius = 0.4,
e1=cbind(0, 0, 1),
e2=cbind(1, 0, 0),
sides=10
)
# ... rotate cylinder horizontally and scale it
len=sqrt(sum(abs(end)*abs(end)))
c=scale3d(c,0.1,0.1,len-cone.length)
# ... Duncan Murdoch's code snipe
rotation <-
rgl:::GramSchmidt(end-start+c(1,0,0),end-start+c(0,1,0),end-start,
order=c(3,1,2))
c <- rotate3d(c, matrix=rotation)
shade3d(addNormals(c), col=mycol)
# ... cone3d from rgl-demos
q1 <- cone3d(qmesh=T,trans=diag(4)) # height=1,radius=1, base at (0,0,0)
q1=translate3d(scale3d(q1,0.15,0.15,1.4),0,0,len-cone.length)
q1=rotate3d(q1, matrix=rotation) # hinlegen ... negative rotation ==
zeigerrrichtung
shade3d(q1,col=mycol) # verschachtelt aufrufen
}
open3d()
vector3D(start=c(0,0,0),end=data[,1], 'red');
vector3D(start=c(0,0,0),end=data[,2],'green')
arrow3d(c(0,0,0),data[,1],color='red');arrow3d(c(0,0,0),data[,2],
color='green')
axes3d(c('x','y','z'));title3d('main','sub','X','Y','Z');box3d()
On 11-08-09 5:22 AM, René Mayer wrote:
Dear List,
I'm trying to draw vector in XYZ with rgl under use of a cylinder3d.
Therefore I scale and rotate a basis-cylinder).
However, somehow the rotation is wrong as
verified by overplotting arrow3d().
Where is my mistake?
I would guess it is in assuming that theta can be computed on the
original vector, not on the rotated one: rotating about the Y axis
changes end[1].
I usually use a Gram-Schmidt type calculation to do this sort of
thing. The undocumented rgl:::GramSchmidt function does this for
3x3 matrices, orthogonalizing by row. So you could replace all 3 of
your rotations (including the first one) by this:
rotation <-
rgl:::GramSchmidt(end-start+c(1,0,0),end-start+c(0,1,0),end-start,
order=c(3,1,2))
c <- rotate3d(c, matrix=rotation)
(I notice you also forgot to translate the cylinders to start; this
doesn't matter in your example, but would if you had a non-zero
origin.)
One problem with this kind of display is that it assumes the
coordinates are all of equal range. If you try plotting one of
these vectors when the range of x, y and z are drastically
different, the cylinders will look really strange.
Duncan Murdoch
library(heplots)
library(rgl)
# ... 2 vectors
data=data.frame(row.names=c('X','Y','Z'), x1=c(2,1,5),y=c(4,3,2))
vector3D=function(start=c(0,0,0), end, mycol='green'){
# ... cylinder as basis-vector
c=cylinder3d(rbind( c(start), # start
c(0,0,1)), # end
radius = 0.2,
e1=cbind(0, 0, 1),
e2=cbind(1, 0, 0),
sides=10
)
# ... rotate cylinder horizontally and scale it
len=sqrt(sum(abs(end)*abs(end)))
c=scale3d(c,0.1,0.1,len)
c=rotate3d(c,-(pi/2),0,1,0)
# ... rotation angles
theta = atan2(end[2],end[1]) # angle in yx-plane for Z-achses rotation
phi = atan2(end[3],sqrt(end[1]^2+end[1]^2)) # angle in zx for Y-achses
rotation
# ... rotation
c=rotate3d(c,phi,0,1,0) # Y-achses rotation
c=rotate3d(c, -theta,0,0,1) # Z-achses rotation
shade3d(addNormals(c), col=mycol)
}
open3d()
vector3D(start=c(0,0,0),end=data[,1], 'red');
vector3D(start=c(0,0,0),end=data[,2],'green')
arrow3d(c(0,0,0),data[,1],color='red');arrow3d(c(0,0,0),data[,2],
color='green')
axes3d(c('x','y','z'));title3d('main','sub','X','Y','Z');box3d()
thanks,
René
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______________________________________________
[email protected] mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
