[R] Playing with rgl: a Youtube video

[Duncan Murdoch]

On 23/12/2009 7:13 AM, Rainer M Krug wrote:
> 
> 
> On Tue, Dec 22, 2009 at 8:10 PM, Duncan Murdoch <murdoch at stats.uwo.ca 
> <mailto:murdoch at stats.uwo.ca>> wrote:
> 
>     On 22/12/2009 12:49 PM, Mark Knecht wrote:
> 
>         On Mon, Dec 21, 2009 at 4:42 AM, Duncan Murdoch
>         <murdoch at stats.uwo.ca <mailto:murdoch at stats.uwo.ca>> wrote:
>          > I've just posted a demo made with the rgl package to Youtube,
>         visible here:
>          >  http://www.youtube.com/watch?v=prdZWQD7L5c
>          >
>          > For future reference, here are the steps I used:
>          >
>          > 1.  Design a shape to be displayed, and then play with the
>         animation
>          > functions to make it change over time.  Use play3d to do it
>         live in R,
>          > movie3d to write the individual frames of the movie to .png
>         files.
>          >
>          > 2.  Use the ffmpeg package (not an R package, a separate
>         project at
>          > http://ffmpeg.org) to convert the .png files to an .mp4 file.
>          The
>          > individual frames totalled about 1 GB; the compressed movie
>         is about 45 MB.
> 
> 
> Could you please post the command line options you used for ffmpeg? I 
> remember I wanted to do an animation, also from .png, and I struggled a lot.

Sure.  The png files were 1024 by 768, designed to be displayed at 
24fps.  The command line was

ffmpeg  -b 2400000 -r 24 -i movie%03d.png -s xga movie.mp4

The -b option controls the target bit rate.  The -r option says how many 
frames per second, -i includes all the files (named things like 
movie001.png, etc.), -s sets the output size, with xga being a quick way 
to say 1024x768, and movie.mp4 is the output file.  There are tons of 
options to change codec, etc., but I found the -b option was the only 
one I needed to play with.

Duncan Murdoch

> 
> Rainer
>  
> 
>          > 3.  Upload to Youtube.  I'm not a musician, so I had to use
>         one of their
>          > licensed background tracks, I couldn't write my own.  I spent
>         a lot of time
>          > picking one and then adjusting the timing of the video to
>         compensate.  Each
>          > render/upload cycle at full resolution took about an hour and
>         a half.  It's
>          > a lot faster to render in a smaller window with fewer frames
>         per second, but
>          > it's still tedious.   It's easier to synchronize if you
>         actually have a copy
>          > of the music locally, but Youtube doesn't let you download
>         their music.  So
>          > the timing isn't perfect, but it's good enough for me!
>          >
>          > Duncan Murdoch
>          >
> 
>         Cool enough video. Thanks for sharing.
> 
>         I'm curious - did you do the equations for the knot in R? If so what
>         did they look like, assuming there's no reason you cannot share it.
>          
> 
> 
>     The knot has equation
> 
>     cbind(sin(theta)+2*sin(2*theta), 2*sin(3*theta),
>     cos(theta)-2*cos(2*theta))
> 
>     The threads in the braid have equation
> 
>     cbind(sin(theta) + sin(2*theta)/2, sin(theta-pi) + sin(2*theta)/2,
>     theta)
> 
>     in the local coordinates of the knot.
> 
>     Overall it's about 100 lines of R code, too ugly to post.
> 
>     Duncan Murdoch
> 
> 
>     ______________________________________________
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>     and provide commented, minimal, self-contained, reproducible code.
> 
> 
> 
> 
> -- 
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> 
> Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation 
> Biology, UCT), Dipl. Phys. (Germany)
> 
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>