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Re: RegionPlot3d under sampling plot points?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99490] Re: RegionPlot3d under sampling plot points?
  • From: dh <dh at metrohm.com>
  • Date: Wed, 6 May 2009 05:29:21 -0400 (EDT)
  • References: <gtp1g4$k4c$1@smc.vnet.net>


Hi,

the problem comes from the fact, that the region becomes very thin 

compared to the plot range. The numerical algorithm seems to have 

problems to decide if the region exists or not.

An easy work around would be make the surface "thick" by deleting the 

inequality: z<= x

or you could make it "thick enough" by specifying e.g.: z <= x + 10000

Daniel



gramathon wrote:

> Hi All,

> I am new to Mathematica, so apologies ahead of time if this is a silly

> problem. I am trying to use RegionPlot3D to plot the following,

> RegionPlot3D[

>  2 x(y - 1) <= 2.5  z+ 2 (y - 1)  z&& z<= x, {x, 1,

>   864000}, {y, 2, 500}, {z, 1, 864000}, PlotStyle -> Orange,PlotPoints-

>> 100]

> 

> The problem is I end up getting gaps in regions where I expect none to

> exist.

> - I tried increasing the PlotPoints.Though that reduces the number of

> gaps at first (partly removes the gaps for the higher values of NA and

> NP but gaps remain, in the lower values of the two axises) after a

> certain number of point >= PlotPoints -> 150the graph ends up looking

> completely different with Spikes everywhere and still has gaps which

> does not make sense....(I am not sure if this could be due to the

> graphics card because the above code is relatively smoother on my less

> powerful machine but still has gaps)

> - I tried providing different plotpoints to different axises E.g.

> PlotPoints-> {111,100,111}... but that did not seem to help either.

> - I tried MaxRecursion as well but that does not seem to help in this

> case either...

> I am completely lost, and have been spending quite a bit of time

> trying to search for an answer...WOULD REALLY APPRECIATE it if anyone

> could Help

> Thanks a bunch GUYS

> Version  7 of Mathematica

> 




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