Re: [R] rgl package and animation

[Robert Baer]

On 11/3/2012 6:47 AM, Duncan Murdoch wrote:
On 12-11-02 7:47 PM, Robert Baer wrote:
I am trying to figure out how to use rgl package for animation.  It
appears that this is done using the play3d() function.  Below I have
some sample code that plots a 3D path and puts a sphere at the point
farthest from the origin (which in this case also appears to be at the
end of the path).  What I would like to do is animate the movement of
another sphere along the length of the path while simultaneously
rotating the viewport.
Duncan Murdock's (wonderful) Braided Knot YouTube video:
   (http://www.youtube.com/watch?v=prdZWQD7L5c)
makes it clear that such things can be done, but I am having trouble
understanding how to construct the f(time) function that gets passed to
play3d().  The demo(flag) example is a little helpful, but I still can't
quite translate it to my problem.

Can anyone point to some some simple f(time) function examples that I
could use for reference or give me a little hint as to how to construct
f(time) for movement along the path while simultaneously rotating the
viewport?

Thanks,

Rob



library(rgl)
# Generate a 3D path
dat <-
structure(list(X = c(0, 0.0618130000000008, 0.00223599999999635,
-0.0308069999999958, -0.172805999999994, -0.372467, -0.587706999999995,
-0.881484999999998, -1.103668, -1.366157, -1.625862, -1.94806699999999,
-2.265388, -2.68982699999999, -3.095001, -3.49749, -3.946068,
-4.395653, -4.772034, -5.111259, -5.410515, -5.649475, -5.73439,
-5.662201, -5.56714599999999, -5.39033499999999, -5.081581, -4.796631,
-4.496559, -4.457024, -4.459564, -4.641746, -4.84910599999999,
-5.08994300000001, -5.43129, -5.76372499999999, -6.199448, -6.517578,
-6.86423499999999, -6.90743999999999), Y = c(0, -0.100724,
-0.169471999999999,
0.0365059999999886, -0.0929950000000019, -0.222977, -0.355759000000006,
-0.365822000000009, -0.329948999999999, -0.209557000000004,
-0.0804140000000046,
0.0201339999999988, 0.295372, 0.138831999999994, 0.281104999999997,
0.223761999999994, 0.141905999999992, 0.0602949999999964,
-0.0933080000000075,
-0.207596000000009, -0.328629000000006, -0.438568000000004,
-0.469109000000003,
-0.623505000000009, -0.525467000000006, -0.568444, -0.638885999999999,
-0.727356, -1.073769, -1.03213500000001, -1.203461, -1.438637,
-1.65023100000001, -1.861351, -2.169083, -2.43147300000001,
-2.69914300000001,
-2.961258, -3.23938000000001, -3.466103), Z = c(0, 0.13552900000002,
0.401062000000024, 1.21637000000004, 1.55395500000003, 1.73080500000003,
1.81167600000003, 2.18512000000004, 2.52603200000004, 3.03479000000004,
3.42654400000004, 3.82251000000002, 4.74490400000002, 4.644837,
5.41848800000002, 5.85867300000001, 6.37835699999999, 6.83395400000001,
7.216339, 7.59411600000004, 7.95590200000004, 8.352936, 
8.70931999999999,
9.01669300000003, 9.48553500000003, 9.90005500000001, 10.397003,
10.932068, 11.025726, 12.334595, 13.177887, 13.741852, 14.61142,
15.351013, 16.161255, 16.932831, 17.897186, 18.826691, 19.776001,
20.735596), time = c(0, 0.0100000000000016, 0.0199999999999996,
0.0300000000000011, 0.0399999999999991, 0.0500000000000007,
0.0600000000000023,
0.0700000000000003, 0.0800000000000018, 0.0899999999999999,
0.100000000000001,
0.109999999999999, 0.120000000000001, 0.129999999999999, 
0.140000000000001,
0.150000000000002, 0.16, 0.170000000000002, 0.18, 0.190000000000001,
0.199999999999999, 0.210000000000001, 0.220000000000002, 0.23,
0.240000000000002, 0.25, 0.260000000000002, 0.27, 0.280000000000001,
0.289999999999999, 0.300000000000001, 0.310000000000002, 0.32,
0.330000000000002, 0.34, 0.350000000000001, 0.359999999999999,
0.370000000000001, 0.379999999999999, 0.390000000000001)), .Names = 
c("X",
"Y", "Z", "time"), row.names = c("1844", "1845", "1846", "1847",
"1848", "1849", "1850", "1851", "1852", "1853", "1854", "1855",
"1856", "1857", "1858", "1859", "1860", "1861", "1862", "1863",
"1864", "1865", "1866", "1867", "1868", "1869", "1870", "1871",
"1872", "1873", "1874", "1875", "1876", "1877", "1878", "1879",
"1880", "1881", "1882", "1883"), class = "data.frame")


# Plot 3d path
with(dat, plot3d(X,Y,Z, type = 'l', col = 'blue', lty = 1))

# get absolute distance from origin
dat$r = sqrt(dat$X ^ 2 + dat$Y ^ 2 + dat$Z ^ 2)
        mr = max(dat$r)  # yes sorry, didn't get copied to original 
email code
mxpnt = dat[dat$r == mr,] # Coordinates of furthest point

# Plot a blue sphere at max distance
plot3d(mxpnt$X, mxpnt$Y, mxpnt$Z, type = 's', radius = 1, col = 'blue',
add = TRUE)


Your code didn't include the mr variable, but I assume it's just 
max(dat$r).  With that assumption, I'd do the animation function as 
follows:

First, draw the new sphere at the first point and save the object id:

sphereid <- sphere3d(dat[1,c("X", "Y", "Z")], col="red", radius=1)

# Also save the spinner that you like:

spin <- spin3d( ) #maybe with different parms

# Now, the animation function:

f <- function(time) {
  par3d(skipRedraw = TRUE) # stops intermediate redraws
  on.exit(par3d(skipRedraw=FALSE)) # redraw at the end

  rgl.pop(id=sphereid) # delete the old sphere
  pt <- time %% 40 + 1 # compute which one to draw
  pnt <- dat[pt, c("X", "Y", "Z")] # maybe interpolate instead?
  sphereid <<- spheres3d(pnt, radius=1, col="red")
  spin(time)
}

Duncan Murdoch

Thanks so much Duncan!

I probably never would have gotten there without your help. (Especially 
since I had to look at the help for the <<- operator, which is 
conceptually a level beyond where I usually work).   It would be great 
to have an additional creative example or two for  f(time) functions in 
the play3d() help.  Your useful code comments really help me see what 
needs to happen in an f(time) function.

I really appreciate that you took the time to get me going!

Rob

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