Re: Restrict domain of Plot3D[]?

• To: mathgroup at smc.vnet.net
• Subject: [mg13115] Re: Restrict domain of Plot3D[]?
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Tue, 7 Jul 1998 03:44:18 -0400
• Organization: University of Western Australia
• References: <6nn9u1\$58g@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```robpeterson at iname.com wrote:

> I'm plotting f[x,y] where x+y<1.  Presently I'm getting this done by
>
> Plot3D[ If[ x+y<1 ], f[x,y], 0], {x,0,1}, {y,0,1}]
>
> Here, the forbidden area where x+y>1 transitions down to the 0 level.
>
> Things are working OK but the transition looks lousy.
>
> Is there some way to just stop the plotting at the boundary where x+y
> become 1?  Or, some other method ?
>
> Any clues will be greatly appreciated.

An answer for this appeared in The Mathematica Journal 5(1):15. Change
variables and reparametrise y:

ParametricPlot3D[{x,u (1-x),f[x,u (1-x)]},{x,0,1},{u,0,1}];

Here y -> u (1-x) and u:[0,1].

Cheers,
Paul

____________________________________________________________________
Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia            Nedlands WA  6907
mailto:paul at physics.uwa.edu.au  AUSTRALIA
http://www.pd.uwa.edu.au/~paul

God IS a weakly left-handed dice player
____________________________________________________________________

```

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