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Re: Why are my 3D plots blue?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114262] Re: Why are my 3D plots blue?
  • From: Joseph Gwinn <joegwinn at comcast.net>
  • Date: Mon, 29 Nov 2010 06:07:39 -0500 (EST)
  • References: <ictfvj$mi6$1@smc.vnet.net>

In article <ictfvj$mi6$1 at smc.vnet.net>, John Fultz <jfultz at wolfram.com> 
wrote:

> If you can move the Dynamic inside of the Graphics3D[], you'll have a much 
> better experience.  I.e., instead of...
> 
> Dynamic[stuff; Graphics3D[{dirs}, opts]]
> 
> do this...
> 
> Graphics3D[Dynamic[stuff; {dirs}], opts]

I will try this.  

Will something like: 

DynamicModule[{local variables},
  Dynamic[stuff];
  Graphics3D[ Dynamic[graphic directives], opts]
]

also work?  I've tried some similar approaches, but the graphics didn't 
respond to mouse motion, don't know exactly why.  I would have thought 
that a local variable x would be linked by the Dynamic functions.  I 
assume I didn't quite do it right.


> and if the options should be dynamically updated, put individual Dynamics in the 
> option values.  

Will this allow me to track the current value of for instance 
ViewMatrix?  I have tried Dynamic[ViewMatrix] to no effect, getting an 
unchanging empty list {} in response.


>  The basic problem here is that the Graphics3D is being recreated 
> over and over again and Mathematica is getting confused about what exactly 
> should be selected.  In typical examples, this kind of thing works fine, but 
> your code, for reasons I haven't investigated, stresses this enough to expose the 
> problem.  By preventing the Graphics3D wrapper from being recreated, you can 
> avoid the problem entirely.

OK.  Sounds like it will be faster too.


Another perhaps related effect discovered by accident is that moving the 
3D mouse while Mathematica is doing the initial evaluation of the notebook can 
cause Mathematica to crash with a SEGFAULT error.  This happened a few 
days ago, and I allowed MacOS to send the crash report to Apple.

The tricky thing is that if one merely puts one's elbow down on the 
table, the 3D mouse jiggles, and will emit a burst of data, so one could 
cause the problem by unlucky timing without touching the mouse.  It 
would appear to the perplexed that Mathematica crashes at random while starting 
up on this notebook.

I've also seen a less dramatic variation in a document that appears to 
be immune to being saved, as the unsaved-changes marker ignores multiple 
save commands - it's the mechanical vibration from typing the save 
command that jiggles the mouse and thus causes a new unsaved change so 
quickly that it seems that the save command was ignored.  (The solution 
here is probably simply telling people that this can happen and not to 
worry.)


Regards,

Joe Gwinn



> Sincerely,
> 
> John Fultz
> jfultz at wolfram.com
> User Interface Group
> Wolfram Research, Inc.
> 
> 
> On Sat, 27 Nov 2010 03:36:43 -0500 (EST), Joseph Gwinn wrote:
> > I've noticed an apparently harmless but mystifying oddity.
> >
> > I have some Graphics3D plots that contain an object that is being moved
> > and rotated by a 3D mouse (a SpaceNavigator).  If the view as initially
> > determined by Graphics3D does not change, one can move the object around
> > forever with no blue.
> >
> > If the view is changed (either by direct mouse click-and-drag action to
> > rotate the bounding box, or automatically as Graphics3D computes a
> > better view), the entire plot window will become see-through pastel
> > blue, the same shade as is used to mark the bracket of a selected cell.
> >
> > If one selects the cell manually before using the 3D mouse to spin the
> > object, the plot does not go blue.
> >
> > In all cases, this is within a DynamicModule and ControllerState is
> > being used to obtain the datastream from the 3D mouse.  There are no
> > messages or errors reported when the plot goes blue.
> >
> > Does anyone know what's going on?  Somehow, the plot is being selected.
> > One assumes that once the cause is understood, it will be obvious how to
> > prevent this annoyance.
> >
> > Thanks,
> >
> > Joe Gwinn
> >
> >
> > For the record, here is the code of one miscreant:
> >
> > DynamicModule[{qd=Q[1,0,0,0],qxr,qyr,qzr,xr,yr,zr,xd,yd,zd,xp=0,yp=0,zp=0
> > },
> >
> > Dynamic[{xp,yp,zp}+=3{-1,1,1}*ControllerState["SpaceNavigator",{"X","Z","
> > Y"}]^3;
> > {xr,yr,zr}=-5ControllerState["SpaceNavigator",{"X Rotation","Z
> > Rotation","Y Rotation"}]^3;
> > qxr=Q[Cos[xr/2],Sin[xr/2],0,0];  (* Generate the X-axis rotation
> > quaternion *)
> > qyr=Q[Cos[yr/2],0,Sin[yr/2],0];  (* Generate the Y-axis rotation
> > quaternion *)
> > qzr=Q[Cos[zr/2],0,0,Sin[zr/2]];  (* Generate the Z-axis rotation
> > quaternion *)
> > qd=qzr**qyr**qxr**qd;  (* Apply the composite rotation to the current
> > direction *)
> > {xd,yd,zd}=SWproduct[{0,0,1},qd];  (* Sandwich product computes the
> > direction vector *)
> > Graphics3D[{Sphere[{xp,yp,zp},0.3],Arrow[Tube[{{xp,yp,zp},{xp,yp,zp}+7{xd
> > ,yd,zd}},0.1]],Text["Log10 Abs Q Norm error=
> > "<>ToString[Log[10,Abs[Norm[qd]-1]]]/2,{0,0,-11.5}]
> > ,Text[ToString[qd],{0,0,-10}] ,Text["DirVec=
> > "<>ToString[{xd,yd,zd}],{0,0,-13}],Text["Loc=
> > "<>ToString[{xp,yp,zp}],{0,0,-14.5}]}
> > ,PlotRange->{{-10,+10},{-10,+10},{-10,+10}},PlotLabel->"Translation plus
> > Quaternion
> > rotation",ViewPoint->Front,ViewVertical->{0,0,1},ViewCenter->{0,0,0},View
> > Vector->{{0,25,0},{0,-1,0}},ControllerLinking->False]]]
> >
> > End code.  SWproduct[] uses a quaternion to rotate an ordinary vector.


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