Re: Re: Problems updating Graphics3D Polygons

*To*: mathgroup at smc.vnet.net*Subject*: [mg77756] Re: [mg77705] Re: Problems updating Graphics3D Polygons*From*: DrMajorBob <drmajorbob at bigfoot.com>*Date*: Sat, 16 Jun 2007 03:25:22 -0400 (EDT)*References*: <12927846.1181901440802.JavaMail.root@m35>*Reply-to*: drmajorbob at bigfoot.com

I'm multiplying the polygon list by a 3x3 matrix. (I posted this before, but just in case...) array[dims] checks the dimensions of its argument, threeD changes a scalar or 3-vector into a 3x3, and scaleZ multiplies the polygon list by that matrix. The multiplication is pts.matrix; pts is n x 3 and matrix is 3x3, so the result is n x 3 again, still suitable as the argument to Polygon. (This could be modified to work for 2D plots as well, but I haven't.) Clear[scale, array, threeD] array[dims_List] = ArrayQ[#] && Dimensions[#] == dims &; threeD[m_?(array[{3, 3}])] := m threeD[m_?(array[{3}])] := DiagonalMatrix@m threeD[f_?NumericQ] := DiagonalMatrix@{1, 1, f} scale[graphics_, m_] := graphics /. Polygon[pts_] :> Polygon[pts.threeD[m]] gobject = Graphics3D[{Polygon[{{0., 0.5, 1.28}, {0., 0., 1.}, {0.5, 0., 1.28}, {0.5, 0.5, 1.64}}], Polygon[{{0.5, 0.5, 1.64}, {0.5, 0., 1.28}, {1., 0., 2.71}, {1., 0.5, 3.49}}]}] scale[gobject, 1/3] scale[gobject, {1, 2, 1}] scale[gobject, RandomReal[{1/2, 3/2}, {3, 3}]] Bobby On Fri, 15 Jun 2007 03:35:22 -0500, chuck009 <dmilioto at comcast.com> wrote: > Thanks. Jean-Marc noticed in my original post that I just didn't call > the function correctly. I like the code you used below, the > pts.{{1,0,0},{0,1,0},{0,0,ratio}}. I see what it does just not sure of > the construct. I'll figure it out though. Thanks! > >> "In[473]:ExpandZ[g_,ratio_]: >> g/.Polygon[pts_]:>Polygon[{#[[1]],#[[2]],#[[3]]*ratio} >> & /@pts];" >> >> There are a couple of "=" signs missing; not sure >> what you're seeing at >> your machine. >> >> This works at mine: >> >> Clear[expandZ] >> expandZ[g_, ratio_] := >> g /. Polygon[pts_] :> >> Polygon[{#[[1]], #[[2]], #[[3]]*ratio} & /@ >> & /@ pts]; >> >> But I prefer >> >> Clear[expandZ] >> expandZ[g_, ratio_] := >> g /. Polygon[pts_] :> >> Polygon[pts.{{1, 0, 0}, {0, 1, 0}, {0, 0, >> 0, 0, ratio}}]; >> > > -- DrMajorBob at bigfoot.com