Re: RegionPlot3d under sampling plot points?

• To: mathgroup at smc.vnet.net
• Subject: [mg99503] Re: [mg99412] RegionPlot3d under sampling plot points?
• From: Ermyas Teshome <ermyasteshome at gmail.com>
• Date: Thu, 7 May 2009 06:31:27 -0400 (EDT)
• References: <200905050941.FAA20778@smc.vnet.net>

```Hi Bob,
Thanks a bunch for that. I will need to play around with the thickness a bit
but I reckon that should do it
Thanks again,
gramathon

On Wed, May 6, 2009 at 3:04 AM, Bob Hanlon <hanlonr at cox.net> wrote:

>
> FullSimplify[Reduce[
>  {2 x (y - 1) <= 5/2 z + 2 (y - 1) z, z <= x, x >= 1, y >= 2,
>   z >= 1}],
>  {z <= x, x >= 1, y >= 2, z >= 1}]
>
> x == z || (z < x < (9*z)/4 && (5*x)/(z - x) + 4*y + 1 <= 0) || (4*x ==
>    9*z && y == 2)
>
> Show[
>  Plot3D[x, {x, 1, 864000}, {y, 2, 500},
>  PlotStyle -> LightBlue],
>  RegionPlot3D[(z < x < (9*z)/4 &&
>       (5*x)/(z - x) + 4*y + 1 <= 0),
>  {x, 1, 864000}, {y, 2, 500}, {z, 1, 864000},
>  PlotStyle -> Lighter[Green]],
>  ParametricPlot3D[{x, 2, 4 x/9}, {x, 1, 864000},
>  PlotStyle -> {AbsoluteThickness[3], Red}]]
>
>
> Bob Hanlon
>
> ---- gramathon <ermyasteshome at gmail.com> 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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