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Re: Re: No Show
*To*: mathgroup at smc.vnet.net
*Subject*: [mg89146] Re: [mg89112] Re: No Show
*From*: Syd Geraghty <sydgeraghty at mac.com>
*Date*: Tue, 27 May 2008 07:13:54 -0400 (EDT)
*References*: <g1bf08$mcv$1@smc.vnet.net> <200805260529.BAA09868@smc.vnet.net>
Hi,
This is a report to the Mathgroup and will also be reported as a bug
to Wolfram support.
I experienced very weird system behaviour evaluating the following
code from Helen's post below:-
> You might also want to set the BoxRatios.
>
> bot = Plot3D[-Sqrt[1 - (x^2 + y^2)], {x, -1, 1}, {y, -1, 1}];
> top = Plot3D[+Sqrt[1 - (x^2 + y^2)], {x, -1, 1}, {y, -1, 1}];
> Show[top, bot, PlotRange -> Automatic, BoxRatios -> {1, 1, 1}]
I would be interested if anyone else can reproduce the problem.
When rotating the graphic output from Show above (A boxed sphere with
3D axes) I could generate what appears as a jumbled ray trace diagram
for the image.
I held the jumbled output and could copy and paste it. I thought I
would paste it into iPhoto and post it on my website so as I could
share the image with Mathgroup or WRI Bug support. Imagine my surprise
when I opened iPhoto and as soon as I scrolled within that window I
started to paint similar raytraced regions on my screen. At this point
I suspected a hardware graphics IC or memory failure.
However I rebooted the system and all seems well. I opened iPhoto and
then Aperture and could scroll thousands of photos OK.
I now suspect a Mathematica bug generated while doing the rotation.
Of course it might still prove to be my system problem. However I can
open the offending Mathematica notebook and still see the saved raytrace
output (without re-evaluation which I avoided so I could send this
email).
My system info is below. Good luck tracking this behaviour WRI!
Cheers ... Syd
Syd Geraghty B.Sc, M.Sc.
sydgeraghty at mac.com
My System
Mathematica 6.0.2.1 for Mac OS X x86 (64 - bit) (March 13, 2008)
MacOS X V 10.5.2
MacBook Pro 2.33 Ghz Intel Core 2 Duo 2GB RAM
On May 25, 2008, at 10:29 PM, Helen Read wrote:
> Narasimham wrote:
>> Why is the following plot, bot, (with - Sqrt) not Shown along with
>> top?
>>
>> Why is it treated only as a plot skeleton, so no combining is
>> possible?
>>
>> bot = Plot3D[-Sqrt[1 - (x^2 + y^2) ] , {x, -1, 1}, {y, -1, 1}]
>> top = Plot3D[+Sqrt[1 - (x^2 + y^2) ] , {x, -1, 1}, {y, -1, 1}]
>> Show[top, bot]
>
> Oh, you are going to get a lot of replies to this. It was discussed at
> length when v.6 was first released. Basically, as of v.6, the default
> behavior of Show is to get the PlotRange from the first plot listed.
> See
> what happens if you reverse it.
>
> Show[bot, top]
>
> The way to get something more like you are expecting is to set
> PlotRange->Automatic within Show.
>
> bot = Plot3D[-Sqrt[1 - (x^2 + y^2)], {x, -1, 1}, {y, -1, 1}];
> top = Plot3D[+Sqrt[1 - (x^2 + y^2)], {x, -1, 1}, {y, -1, 1}];
> Show[top, bot, PlotRange -> Automatic]
>
> You might also want to set the BoxRatios.
>
> bot = Plot3D[-Sqrt[1 - (x^2 + y^2)], {x, -1, 1}, {y, -1, 1}];
> top = Plot3D[+Sqrt[1 - (x^2 + y^2)], {x, -1, 1}, {y, -1, 1}];
> Show[top, bot, PlotRange -> Automatic, BoxRatios -> {1, 1, 1}]
>
> I greatly dislike this new behavior of Show, for what it's worth. The
> folks at WRI argue that because of all the new graphics options (e.g.,
> Filling), it would not make sense to combine the PlotRange
> automatically
> (as Show did in previous versions of Mathematica). Personally, I
> find it
> to be a pain in the neck to have to ask for PlotRange->Automatic
> virtually every time I use Show, and my students often forget and get
> burned by it. I would much prefer PlotRange->Automatic to be the
> default
> in Show, and to set my own PlotRange manually on those infrequent
> occasions when I need something else. And as for the argument that
> setting a PlotRange automatically from the combined plots isn't always
> appropriate, why not provide an easy way to tell Show to use the
> PlotRange from a particular plot? Something like PlotRange->{1} to get
> the PlotRange from the first plot, PlotRange->{2} to get the range
> from
> the 2nd plot, etc., would do the job when needed, and still allow
> PlotRange->Automatic (which for me is almost always what I want) to be
> the default.
>
> I just now discovered, BTW, that
>
> SetOptions[Show, PlotRange -> Automatic]
>
> does not even work. It generates an error message claiming that
> "PlotRange is not a known option for Show".
>
> --
> Helen Read
> University of Vermont
>
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