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Re: work only with Performance->Speed

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102838] Re: work only with Performance->Speed
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Sat, 29 Aug 2009 06:30:45 -0400 (EDT)

On 8/27/09 at 6:32 AM, btreat1 at austin.rr.com (DrMajorBob) wrote:

>You have an extra comma (syntax error!), but this fails, too:

>ContourPlot3D[
>zz (-1 + 1/(xx^2 + yy^2 + zz^2)^(3/2)), {xx, -2, 2}, {yy, -2, 2},
>{zz, -4, 4}, BoundaryStyle -> Red, RegionFunction -> Function[{x, y,
>z}, x^2 + y^2 + z^2 >= 1], PerformanceGoal -> "Quality"]
>
>"Speed" works, but "Quality" does not. It looks like a bug to me.

I am not so sure this is a bug. The expression becomes 0+0/0 for
xx=yy=zz=0. When "Speed" is chosen, I assume the algorithm
samples the expression at far fewer points and likely misses the
singularity. Conversely, when "Quality" is chosen the
singularity isn't missed. I would guess the issue is due to the
presence of this singularity.



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