Re: Anomolous behaviour of Penrose Triangle Demonstration

*To*: mathgroup at smc.vnet.net*Subject*: [mg81135] Re: Anomolous behaviour of Penrose Triangle Demonstration*From*: WetBlanket <Wyvern864 at gmail.com>*Date*: Thu, 13 Sep 2007 06:32:52 -0400 (EDT)*References*: <200709110923.FAA26497@smc.vnet.net><fc8689$lqa$1@smc.vnet.net>

On Sep 12, 2:59 am, Curtis Osterhoudt <c... at lanl.gov> wrote: > Hi, Syd, > > I have no real insight. I confirm that changing the ViewPoint prefactor > causes the same behavior on my machine. I did not try to evaluate the code > which allows "vp" to be changed via a slider; just rotating the graphic > produced by the first chunk of code causes part of it to disappear (somewhat > randomly). > Of course, I've been having lots of problems with my ATI drivers not being > compatible with Mathematica 6.0's Graphics3D[] objects, so this may be a > symptom of that. > > This is on "6.0 for Linux x86 (32-bit) (June 19, 2007)". > > On Tuesday 11 September 2007 03:23:52 you wrote: > > > > > I would appreciate some insight regarding the Penrose Triangle > > Demonstration which can be found at:- > > > http://demonstrations.wolfram.com/PenroseTriangle/ > > > The original source I downloaded when run on my machine displayed a > > blank panel! > > (The demonstration ran fine on my machine in "watch web preview" mode!) > > > $Version Out[1]= "6.0 for Mac OS X x86 (32-bit) (June 19, 2007)" > > > The demonstration source was;- > > > Manipulate[ > > cu[x_, y_, z_, d_] := > > Cuboid[ {x - d/2, y - d/2, z - d/2}, {x + d/2, y + d/2, z + d/2} ]; > > Graphics3D[ > > {Opacity[o], > > cu[0, 15, 30, 7.5], cu[15, 45, 0, 7.5], > > Table[cu[0, 0, 15 n, 7.5], {n, 0, 3}], > > Table[cu[0, 15 n, 0, 7.5], {n, 3}] > > } , > > ViewPoint -> 200 {-1, -1, 1}, > > Boxed -> False, > > PlotRange -> 50 {{-1, 0.8}, {-0.6, 1}, {-0.08, 1}}, > > ImageSize -> {400, 400} > > ], > > {{o, 1, "opacity"}, 0, 1}, TrackedSymbols :> Manipulate] > > > I changed the "viewpoint factor" in ViewPoint -> 200 {-1, -1, 1} > > above to 100{-1, -1, 1} on a hunch and the panel > > displayed correctly. > > > After failing to find any documentation for the use of the "viewpoint > > factor" I tried setting a range for vp and generating a slider in > > addition to opacity to see the effects. > > > Manipulate[ > > cu[x_, y_, z_, d_] := > > Cuboid[ {x - d/2, y - d/2, z - d/2}, {x + d/2, y + d/2, z + d/2} ]; > > Graphics3D[ > > {Opacity[o], > > cu[0, 15, 30, 7.5], cu[15, 45, 0, 7.5], > > Table[cu[0, 0, 15 n, 7.5], {n, 0, 3}], > > Table[cu[0, 15 n, 0, 7.5], {n, 3}] > > } , > > ViewPoint -> vp {-1, -1, 1}, > > Boxed -> False, > > PlotRange -> 50 {{-1, 0.8}, {-0.6, 1}, {-0.08, 1}}, > > ImageSize -> {400, 400} > > ], > > {{o, 1, "opacity"}, 0, 1}, {{vp, 10, "ViewPoint Factor"}, 10, > > 200, 10}, > > TrackedSymbols :> Manipulate] > > > The effects of using the vp slider are very odd. Bits of the graphic > > start disappearing! > > > Any clues as to what is happening here would be appreciated. > > > Yet another strange "feature" showed up when I tried to "Save As" the > > modified demonstration code. > > > I cannot successfully save the modified demonstration. > > > I suspect that is a WRI safeguard for protecting the integrity of the > > Demonstrations Project (which is fine by me). > > > I can of course save the modified code in a new blank notebook. > > > Syd Geraghty > > -- > ========================================================== > Curtis Osterhoudt > cfo at remove_this.lanl.and_this.gov > PGP Key ID: 0x4DCA2A10 > Please avoid sending me Word or PowerPoint attachments > Seehttp://www.gnu.org/philosophy/no-word-attachments.html > ========================================================== I am running on a Dell XPS Laptop using Windows XT and the code seems to work -- nothing much happens when I move the viewpoint slider -- the display moves slightly -- nothing more. Gary

**Follow-Ups**:**Re: Re: Anomalous behaviour of Penrose Triangle Demonstration***From:*Syd Geraghty <sydgeraghty@mac.com>

**References**:**Anomolous behaviour of Penrose Triangle Demonstration***From:*Syd Geraghty <sydgeraghty@mac.com>