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MathGroup Archive 1998

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Re: Very slow graphics rendering

  • To: mathgroup at smc.vnet.net
  • Subject: [mg14179] Re: Very slow graphics rendering
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Wed, 30 Sep 1998 02:04:25 -0400
  • Organization: University of Western Australia
  • References: <6unfa9$o75@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

julio vera wrote:

>  With their help, I could make a graphic of part of a 3D object, like
> this piece of a sphere:
> 
> ParametricPlot3D
> [{x , y , If[ x^2 + y^2 < (4/5)^2 , Sqrt [ 1 - x^2 - y^2 ] ] } , {x , -1
> , 1 , 1/75} , { y, -1 , 1 , 1/75} ]

For such a function you could use Plot3D directly: 

  Plot3D[If[x^2 + y^2 < (4/5)^2, Sqrt[1 - x^2 - y^2], 
	Sqrt[1 - (4/5)^2]], {x, -1, 1}, {y, -1, 1},
		PlotPoints->30,Mesh->False];

However, an alternative (polar) parameterization might be better:

ParametricPlot3D[{r*Cos[t], r*Sin[t], 
    If[r < 4/5, Sqrt[1 - r^2], Sqrt[1 - (4/5)^2]]}, 
		{r, 0, 4/5}, {t, 0, 2*Pi}]; 

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.physics.uwa.edu.au/~paul

            God IS a weakly left-handed dice player
____________________________________________________________________


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