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Re: Two questions



Hy Selwyn,

> I have two questions that I hope someone can help me with.
> 
> 1) Is there a way to use Plot3D to create a ``wireframe" surface
> plot---that is, showing only the grid curves? (No, Shading->False is
> not what I'm after. I want the plot to be _transparent._) If not, is
> there a better way to do it than plotting curves with ParametricPlot3D?
> 

Plot3D[] returns a SurfaceGraphics[]-object. The first argument is a
matrix of f(x,y) at the points where the grid is evaluated.

At first You must convert the surface graphics into a ordinary 
Graphics3D[] object with Polygon[] primitives. You can do this with

surf=Plot3D[f[x,y],{x,x1,x2},{y,y1,y2}]

gr3d=Graphics3D[surf] 

Now You can load the package Graphics`Shapes` it comes with a
WireFrame[] function that does what You want or if You forgot to load
the package You can use the rule

Show[gr3d /. Polygon[pnts_] :> Line[Append[pnts,First[pnts]]]]

> 2) I am continually forgetting to load a package before entering a
> command that it contains. Is there a way to get out of the resulting
> jam without quitting the kernel?

At MathSource in the Enhancements/System folder You will find the
Unshadow package that removes all symbols from the Global context that
is present in other contexts.


Hope that helps
  Jens



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