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Re: Why are my 3D plots blue?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114245] Re: Why are my 3D plots blue?
  • From: John Fultz <jfultz at wolfram.com>
  • Date: Sun, 28 Nov 2010 06:55:19 -0500 (EST)

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]

and if the options should be dynamically updated, put individual Dynamics in the 
option values.  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, stress this enough to expose the 
problem.  By preventing the Graphics3D wrapper from being recreated, you can 
avoid the problem entirely.

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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