| cylinder3d {rgl} | R Documentation |
This function converts a description of a space curve into a "mesh3d"
object forming a cylindrical tube around the curve.
cylinder3d(center, radius = 1, twist = 0, e1 = NULL, e2 = NULL, e3 = NULL,
sides = 8, closed = 0, debug = FALSE)
center |
An n by 3 matrix whose columns are the x, y and z coordinates of the space curve. |
radius |
The radius of the cross-section of the tube at each point in the center. |
twist |
The amount by which the polygon forming the tube is twisted at each point. |
e1, e2, e3 |
The Frenet coordinates to use at each point on the space curve. |
sides |
The number of sides in the polygon cross section. |
closed |
Whether to treat the first and last points of the space curve as identical,
and close the curve. If closed > 0, it represents the number of points of
overlap in the coordinates. |
debug |
If TRUE, display the local Frenet coordinates at each point. |
The number of points in the space curve is determined by the vector lengths in center,
after using xyz.coords to convert it to a list. The other arguments
radius, twist, e1, e2, and e3 are extended to the same
length.
The three optional arguments e1, e2, and e3 determine the local
coordinate system used to create the vertices at each point in center. If missing, they
are computed by simple numerical approximations. e1 should be the tangent coordinate,
giving the direction of the curve at the point. The cross-section of the polygon will be orthogonal
to e1. e2 defaults to an approximation to the normal or curvature vector; it is
used as the image of the y axis of the polygon cross-section. e3 defaults
to an approximation to the binormal vector, to which the x axis of the polygon maps. The
vectors are orthogonalized and normalized at each point.
A "mesh3d" object holding the cylinder.
Duncan Murdoch
# A trefoil knot
open3d()
theta <- seq(0, 2*pi, len=25)
knot <- cylinder3d(cbind(sin(theta)+2*sin(2*theta), 2*sin(3*theta), cos(theta)-2*cos(2*theta)),
e1=cbind(cos(theta)+4*cos(2*theta), 6*cos(3*theta), sin(theta)+4*sin(2*theta)),
radius=0.8, closed=TRUE)
shade3d(addNormals(subdivision3d(knot, depth=2)), col="green")