Re: Any last-minute fixes or requests for inclusion in 4.6.2?

[Daniel J S. <dan...@ie...>]

On 03/10/2013 12:14 AM, sfeam (Ethan Merritt) wrote:
> Anyone know of an unresolved 4.6 bug that should be fixed before
> releasing 4.6.2?   If not, I plan to put the usual source tarball
> on SourceForge later this week.

The one concern is the description for this new item:

> * NEW hidden3d can handle occlusion by pm3d surfaces (as in hidden2.dem)

which seems to me like overselling things a bit.  pm3d has always 
occluded whatever is behind it, so that is not new.  The example 
actually has the pm3d surface on the bottom layer.

What's new is the invisible line type (-2) for hidden surface mesh.  In 
the example, the invisible line type partially covers up the axes which 
doesn't look good.  To see this, after the hidden2.dem demo, type

splot x*x-y*y with lines lt 1 lc rgb "#000000", \
       f(x,y) with lines lt -2 notitle

Also, the meshes don't occlude the pm3d surfaces (the surfaces show 
through the mesh), so that too isn't doing any type of occlusion.  It's 
like going backward from hidden3d.  What would be nice (and something 
I've wanted to work on but can't find the time) is an actual hidden 3D 
surface feature using the mesh sectioning as a starting point.

I'm not saying that plot example isn't something that someone wouldn't 
want to do.  I realize gnuplot doesn't work this way, but there has been 
discussion about making the range specification within the plot command 
apply to just the plot that follows it.  If that were the case, one 
could create a plot similar to hidden2d.dem with the following

unset hidden3d
set zrange [-100:100]
splot [][][-110:0] x*x-y*y with lines lt 1 lc rgb "#000000", \
       f(x,y) with pm3d, \
       [][][0:100] x*x-y*y with lines lt 1 lc rgb "#000000" notile

But even that isn't the best solution (actually bad, but if needing a 
plot from a particular angle, it would do) because if one were to rotate 
the plot to look from a "underneath", the order of plots would no longer 
be correct.

What would really be desirable is the ability to specify which surfaces 
should occlude and which shouldn't.  I actually think that is a very 
useful feature to have.  That way one could specify an interior surface 
that should always show through, which is what the hidden2d example 
effectively doing as observed.  So, here might be how that works:

set hidden3d
f(x,y) = sin(-sqrt((x+5)**2+(y-7)**2)*0.5)
splot f(x,y) with pm3d solid, \
       x*x-y*y with lines lt 1 lc rgb "#000000" transparent


Well, in summary, rather than describing this as a pm3d-related feature, 
how about

  * NEW hidden3d invisible lines for simulated surface occlusion (as in 
hidden2.dem)

Dan