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MathGroup Archive 2001

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RE: 3d Graphics problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28952] RE: [mg28939] 3d Graphics problem
  • From: "David Park" <djmp at earthlink.net>
  • Date: Mon, 21 May 2001 00:43:39 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Francisco,

Your main problem is that you do not have a proper Viewpoint for showing the
line. The line is behind the Polygon. The following works.

Show[{gg1, gg2}, ViewPoint -> {-0.798, -3.080, -1.153}];

I have found that producing various graphics elements and then combining
them with the Show statement is often quite confusing. In your case, you can
build up the entire piece of graphics within one cell, simply by drawing the
elements one after the other and using the desired graphics directives. I
have taken your example, made the line double thickness, and added
differently colored points at the ends of the line and the corners of the
polygon. This is how I would do it:

Needs["Graphics`Colors`"]

Module[{poly, line, pts1, pts2},
    line = Line[{{0.4, 0.3, 0.2}, {0.7, 0.15, 0.15}}];
    poly = Polygon[{{1, 0, 0}, {0, 1, 0}, {0, 0, 1}}];
    pts1 = Point /@ line[[1]];
    pts2 = Point /@ poly[[1]];
    Show[Graphics3D[
    {poly,
     Blue, AbsoluteThickness[2], line,
     AbsolutePointSize[6], Red, pts1,
     Peacock, pts2}],
     AspectRatio -> Automatic, PlotRange -> Automatic,
     {ViewPoint -> {-0.798, -3.08, -1.153}}]];

If you use the DrawingCube package, at my web site, you can stay with the
same paradigm and even add in curves and surfaces produced by any 3D plot
routines. For example, you just use ParametricDraw3D instead of
ParametricPlot3D.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/


> From: FRANCISCO GUTIERREZ [mailto:rpena at elsitio.net.co]
To: mathgroup at smc.vnet.net
>
> Dear NG:
> I have the following problem.  I want to draw a 2D simplex in a 3D space,
> and within the simplex some points and lines.
>
> First I create the line:
> gg1 = Graphics3D[Line[{{0.4, 0.3, 0.2}, {0.7, 0.15, 0.15}}]]
> The the simplex:
> gg2 = Graphics3D[Polygon[{{1, 0, 0}, {0, 1, 0}, {0, 0, 1}}]]
> Then I visualize both:
> Show[{gg1, gg2}, ViewPoint -> {1, 1.5, 2.5}]
> The line isn't visible.  When I draw points, they are not visible either.
> If I give options to the line (thickness, or RGBColor) or to the points, I
> get an error message.
> How should I proceed?
> Thanks,
> Fg
>



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