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Topic: dark halo around gaussian peak in Plot3D?
Replies: 9   Last Post: Mar 10, 2013 12:47 AM

 Messages: [ Previous | Next ]
 David Park Posts: 1,560 Registered: 5/19/07
Re: dark halo around gaussian peak in Plot3D?
Posted: Mar 9, 2013 5:26 AM

Michael,

It looks to me like a numeric problem with very small numbers. You can work
around it by clipping the function. Here I also scaled up the function by
100 just to get a convenient range.

Plot3D[100 Clip[
PDF[BinormalDistribution[0], {x, y}], {10^-150, 20}], {x, -40,
40}, {y, -40, 40},
PlotRange -> All,
PlotPoints -> 30,
Mesh -> None]

If you decrease the lower Clip value by much you will get the "dark halo"
back. It seems to be associated with the front FaceForm losing its color.

Plot3D[100 Clip[
PDF[BinormalDistribution[0], {x, y}], {10^-200, 20}], {x, -40,
40}, {y, -40, 40},
PlotStyle -> Directive[FaceForm[Gray, Red]],
PlotRange -> All,
PlotPoints -> 30,
Lighting -> "Neutral",
Mesh -> None]

David Park
djmpark@comcast.net
http://home.comcast.net/~djmpark/index.html

From: Michael B. Heaney [mailto:mheaney@alum.mit.edu]

Here is simple example that demonstrates the problem:

Plot3D[PDF[BinormalDistribution[0], {x, y}], {x, -40, 40}, {y, -40, 40},

PlotRange -> All, PlotPoints -> 200]

Thanks,

Michael

On Thu, Mar 7, 2013 at 8:49 PM, Bob Hanlon <hanlonr357@gmail.com> wrote:

> I don't see a "dark halo" with the following
>
> Plot3D[
> PDF[BinormalDistribution[0], {x, y}], {x, -3, 3}, {y, -3, 3}]
>
> Can you send a simple example that demonstrates the problem?
>
>
> Bob Hanlon
>
>
> On Thu, Mar 7, 2013 at 10:51 PM, Michael B. Heaney
> <mheaney@alum.mit.edu>
> wrote:

> >
> > Hi,
> >
> > When I plot a gaussian peak in Plot3D, there is a dark halo around
> > the peak. Why is this? How can I get rid of it?
> >
> > Thanks,
> >
> > Michael
> >
> > --
> > ----------------------------------------------------------
> > Michael B. Heaney
> > 3182 Stelling Drive
> > Palo Alto, CA 94303 USA
> > mheaney@alum.mit.edu
> > ----------------------------------------------------------
> >
> >

>

--
----------------------------------------------------------
Michael B. Heaney
3182 Stelling Drive
Palo Alto, CA 94303 USA
mheaney@alum.mit.edu
----------------------------------------------------------

Date Subject Author
3/8/13 Bob Hanlon
3/8/13 Michael B. Heaney
3/9/13 David Reiss
3/9/13 Bob Hanlon
3/9/13 Bob Hanlon
3/9/13 Michael B. Heaney
3/9/13 David Park
3/10/13 Michael B. Heaney