persp box occlusion bug (PR#202)

[wsi@gcal.ac.uk]

Full_Name: Bill Simpson
Version: 64.1
OS: linux
Submission from: (NULL) (193.62.250.209)


Bug in persp() bounding box:
If the surface being plotted extends below the lower z-axis boundary, the box
is
drawn with the wrong occlusion. The box is shown as being occluded by the
surface
even though it should be in front of the surface.

The box is correct for surface extending above the box. Problem is only for
surface extending below the box.

This exhibits the bug:

std<-rep(seq(-32,32,8),9)/1000 * 60
cf<-rep(seq(-32,32,8),rep(9,9))/1000 *60 
dp<-(cf-std)/.6
std<-unique(std)
cf<-unique(cf)
dp<-t(matrix(dp,length(cf),length(std)))
persp(std,cf,dp, xlim=c(-2,2), ylim=c(-2,2), zlim=c(0,5),theta=-40,    
phi=45,
box=TRUE,ltheta=-120, lphi=120,
d=1.5, shade=.7)


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