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Adding markers on the surface of a Plot3D?

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  • Subject: [mg89328] Adding markers on the surface of a Plot3D?
  • From: AES <siegman at>
  • Date: Fri, 6 Jun 2008 06:45:11 -0400 (EDT)
  • Organization: Stanford University

I'd like to highlight the two mesh lines that pass through a certain 
central point -- let's call it the point {xc,yc} -- on a Plot3D by 
thickening those two lines relative to the other mesh lines, or giving 
them a distinctive color, or . . . 

Or put a dot on the surface at the point {xc, yc, f[xc,yc]} to identify 
this location on the surface . . .

Or run a vertical "post" up through that point using something like 
Line[{xc, yc, 0}, {xc, yc, 2*f[xc,yc]}}] (with the part of the post 
below the surface not being seen if you look at the surface from 
above) . . .

I think I've so far tested and confirmed every possible way in which 
each of these tasks _can't_ be done . . .

[And would someone want to help me understand _why_  the 
Show[ - - - - -] command (followed by a semicolon) no longer works, or 
can no longer be used, as one of a sequence of multiple expressions 
within a longer cell?  And why it can't even have a semicolon following 
it as the last line in a cell?  I just can't envision the logic of why 
this was a necessary (or optional?) interface design decision -- isn't 
Show[---] an expression?]

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