playgltf.Rd.gltf and .glb files can contain animation instructions.
This function interprets them and plays them.
playgltf(gltf, animation = 0,
start = times[1], stop = times[2],
times = gltf$timerange(animation),
method = c("rigid", "wholeScene", "partialScene"),
speed = 1, by = NULL, verbose = FALSE, ...)
showNodes(gltf, animation = 0,
start = times[1], stop = times[2],
times = gltf$timerange(animation),
speed = 1, by = NULL)A "gltf" object.
Which animation from the object? An integer from 0 to the
number of animations defined in gltf.
Starting and stopping times.
An alternate way to specify start and stop.
Which drawing method to use? See details below.
Control the updates; see details below.
Whether to print status updates.
Parameter settings to pass to plot3d.rglscene (and hence
to open3d).
glTF files are animated by time dependent changes to the
transformations in their nodes. Those transformations
correspond to RGL par3d("userMatrix") settings in
subscenes and can sometimes be directly imported as such.
However, glTF files also support "skins", a computer graphics concept not supported in RGL. A skin is a way to say that different vertices of the same object (typically a triangle mesh) respond to different nodes. This allows shapes to be stretched, similar to skin on a moving body. RGL assumes that all graphics objects are rigid.
The playgltf function provides partial support for
skins. Using the "wholeScene" method, it can modify the vertices of an entire scene
and redraw the scene. Typically this is quite slow, and
not very satisfactory. The "partialScene" method
allows only the
changed objects to be redrawn, which might help speed things up.
Finally, the "rigid" method converts all polygons
to rigid ones that are supported by rgl, so that motion
is done by changes to the transformations. This is likely the fastest
method, but for some animations the errors introduced by the
conversion are unacceptably large.
The showNodes function displays each node number as
text at the origin for that node. By default it plays the
animation showing how the nodes move.
For both functions, the speed and by arguments
specify the “times” at which the animation is drawn. If
by is specified, then a frame is drawn at time start and
subsequent frames increment the time by by. If it is
NULL (the default), then the speed argument is used
as a multiplier on the internal time (taken to be in seconds).
For example, with the default speed = 1, the first frame will
be drawn at time start, and when it is complete, the next one
will be drawn according to how many seconds have passed in real time,
etc.
Called for the side effect of drawing the animation.
if (interactive() && !rgl::in_pkgdown_example()) {
# This example is fast enough using the "whole" method:
gltf1 <- readGLB(system.file("glb/RiggedSimple.glb", package = "rgl2gltf"))
playgltf(gltf1, start = 0, stop = 3, method = "whole")
# It looks terrible using the "rigid" method, because some triangles
# need to be deformed:
playgltf(gltf1, start = 0, stop = 3, method = "rigid")
# This example is too slow using anything but "rigid", but it's fine there:
samples <- "https://raw.githubusercontent.com/KhronosGroup/glTF-Sample-Models/master/2.0"
gltf2 <- readGLB(paste0(samples, "/BrainStem/glTF-Binary/BrainStem.glb?raw=true"))
playgltf(gltf2, start = 0, stop = 2, speed = 0.25, method = "rigid")
}