Re: Showing the points on a surface about a circle in the plane

• To: mathgroup at smc.vnet.net
• Subject: [mg74901] Re: Showing the points on a surface about a circle in the plane
• From: dh <dh at metrohm.ch>
• Date: Tue, 10 Apr 2007 06:01:30 -0400 (EDT)
• References: <evab9r\$d8v\$1@smc.vnet.net>

```
Hi

here is an example using a simple solution of building up the picture

from several parts:

fun1[x_,y_]:=x^2+y^2;

g1=Plot3D[fun1[x,y],{x,-1,1},{y,-1,1},ColorFunction\[Rule](Hue[1. #]&)]

r=0.8;

g2=ParametricPlot3D[r{Sin[p],Cos[p],0},{p,0,2Pi}];

g3=ParametricPlot3D[{r Sin[p],r Cos[p],0.01+fun1[r Sin[p],r

Cos[p]]},{p,0,2Pi}];

Show[g1, Graphics3D [Thickness[0.01]], g2, g3]

as you will note, there is a problem with the visibiliyt of the

projection of the circle onto the surface. Because of this, I drawed the

projection slighlty (0.01) above the surface.If you want to look at the

surface from below, you would better draw the projection slightly below

the surface.

Daniel

ahallam at iastate.edu wrote:

> What I would like to do with Plot3D and ParametricPlot3D is show a

> surface in three dimensions, a circle in the plane and the points on

> the surface above the circle.  This is what I have in mind where I

> have a square in the plane.  I simply don't know of a way to handle

> the circle.  If there were am ImplicitPlot3D, I can think so some

> options.

>

> I am not sure how to send code so that it is readable so I am simply

> pasting as is.

>

> Someone can yell at me and tell me this is wrong and how to do it

> correctly and then I will.

>

>

```

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