R help - Jun 2012 - Double-buffering problem, this time with an example.

Most of my animations that used to work
on windows() version 2.11.1 and earlier now flash
as if the double buffering is turned off or buffer swapping
is triggered by other events than in the past.

The simplified example below using symbols
should illustrate the problem in a windows environment.

windows()

radius <- 8
n <- 6
ang <- seq(0,2*pi,length=n+1)[-(n+1)]
ca <- cos(ang)
sa <- sin(ang)
size <- c(.1, .3, .5, .7, .9, 1)

colors <-  rainbow(length(size))

for (i in 1:1000){
   radius <- radius*.998
   bnd <- (radius+1)* c(-1, 1)
   cenX <- radius*ca
   cenY <- radius*sa
   symbols(cenX, cenY, circles = size,
           xlim=bnd, ylim=bnd, bg=colors)
}

I have not isolated the version  when the flashing
started but it somewhere between
2.11.1 and 2.14.1.

I did some searching on double-buffering
problems in R but didn't find indications
of this particular problem.

Slowing the animation down did not help.

Dan

For the record, I confirm Dan's description on Windows:
> sessionInfo()
R version 2.15.0 (2012-03-30)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] tools_2.15.0

-- Bert

On Sat, Jun 2, 2012 at 1:02 PM, Daniel Carr <dcarr at gmu.edu>
wrote:
> Most of my animations that used to work
> on windows() version 2.11.1 and earlier now flash
> as if the double buffering is turned off or buffer swapping
> is triggered by other events than in the past.
>
> The simplified example below using symbols
> should illustrate the problem in a windows environment.
>
> windows()
>
> radius <- 8
> n <- 6
> ang <- seq(0,2*pi,length=n+1)[-(n+1)]
> ca <- cos(ang)
> sa <- sin(ang)
> size <- c(.1, .3, .5, .7, .9, 1)
>
> colors <- ?rainbow(length(size))
>
> for (i in 1:1000){
> ?radius <- radius*.998
> ?bnd <- (radius+1)* c(-1, 1)
> ?cenX <- radius*ca
> ?cenY <- radius*sa
> ?symbols(cenX, cenY, circles = size,
> ? ? ? ? ?xlim=bnd, ylim=bnd, bg=colors)
> }
>
> I have not isolated the version ?when the flashing
> started but it somewhere between
> 2.11.1 and 2.14.1.
>
> I did some searching on double-buffering
> problems in R but didn't find indications
> of this particular problem.
>
> Slowing the animation down did not help.
>
> Dan
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm

On 12-06-02 4:02 PM, Daniel Carr wrote:
> Most of my animations that used to work
> on windows() version 2.11.1 and earlier now flash
> as if the double buffering is turned off or buffer swapping
> is triggered by other events than in the past.
>
> The simplified example below using symbols
> should illustrate the problem in a windows environment.
>
> windows()
>
> radius<- 8
> n<- 6
> ang<- seq(0,2*pi,length=n+1)[-(n+1)]
> ca<- cos(ang)
> sa<- sin(ang)
> size<- c(.1, .3, .5, .7, .9, 1)
>
> colors<-  rainbow(length(size))
>
> for (i in 1:1000){
>     radius<- radius*.998
>     bnd<- (radius+1)* c(-1, 1)
>     cenX<- radius*ca
>     cenY<- radius*sa
>     symbols(cenX, cenY, circles = size,
>             xlim=bnd, ylim=bnd, bg=colors)
> }
>
> I have not isolated the version  when the flashing
> started but it somewhere between
> 2.11.1 and 2.14.1.
>
> I did some searching on double-buffering
> problems in R but didn't find indications
> of this particular problem.
>
> Slowing the animation down did not help.
I don't think there was ever a guarantee that double buffering would be 
sufficient for what you were doing:  you just got lucky.

What you need to do (and this should work, at least on the windows() 
device and some others), is use dev.hold() to stop redrawing, and 
dev.flush() when you are ready to display the new stuff.  Your loop 
becomes something like this:

for (i in 1:1000){
    dev.hold()
    radius <- radius*.998
    bnd <- (radius+1)* c(-1, 1)
    cenX <- radius*ca
    cenY <- radius*sa
    symbols(cenX, cenY, circles = size,
            xlim=bnd, ylim=bnd, bg=colors)
    dev.flush()
}

The dev.hold() function was introduced in 2.14.0.  I think dev.flush() 
existed earlier, but not for all systems.

Duncan Murdoch