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3D wireframes again

Al2000
1-Newbie

3D wireframes again

Hi, guys! My best wishes for a Happy New year!

So I have a small cluster of points in space and I wanted to draw a wireframe. After thinking the problem an undetermined time, I finally got a working function to do the job. Guess what: a subsequent search in the collaboratory let me know that Tom had solved the problem many years before, he he he.

So this time I decided search first and program after 🙂

I have a small group of points in space that are generated by a function. I don't know before hand where is each point in space. Generating all the possible connections is easy



but the internal lines are distracting and I prefer if possible not to draw them



Now I'm facing the job of programming a function to find the enclosing polyhedron of a cluster of points. I'm still in the pre-production stage :), i.e. exchanging ideas with my pillow.

So far I know how to detect the outer faces of the polyhedron (using basic vector algebra) but it takes combin(n,3)*(n-3) checks, and I still need to decide how to manage faces of more than 3 coplanar points.

Well, any hint is welcome. Please don't refer me to amazing graphics etc, I'm using Mathcad 2001 and I can only open the oldest sheets.

Saludos,

Al
6 REPLIES 6
RichardJ
19-Tanzanite
(To:Al2000)

Take a look at this thread:

http://collab.mathsoft.com/read?65021,11e#65021

I think what you want is 3D version of what this thread discusses.

Richard

From http://collab.mathsoft.com/read?129868,15e#129868 attached is the mc2k version.

The wireframe routine don't do all what you need, but shows how given the distance between endpoints this information is collected to authomatically draw the linkage bar system.

If you can construct a matrix with values only where you want connect points, I think that you have the solution.

Regards. Alvaro.

Thanks Richard, gracias Alvaro, for your time. I already got one half of the routine working and tonight I found a piece of knowledge I was missing in one of the Tom's sheets.

Saludos,

Al

"Well, any hint is welcome. Please don't refer me to amazing graphics etc, I'm using Mathcad 2001 and I can only open the oldest sheets."
_________________________

You may think in term of the surface plot operator.
Just as a conceptual approach [hint].

jmG

On 1/10/2010 11:23:58 AM, jmG wrote:
>You may think in term of the
>surface plot operator.
>Just as a conceptual approach
>[hint].

Thanks Jean, I already finished the damn function.



Because I know now how to find the faces of the polyhedron, other options are available, as calculating the area, volume and center of mass. Also making a surface plot, but I still need to understand how is coded the data. I will study your attached sheet as well as an old sheet to draw a cube, but not yet. My Dec vacation already ended and I have few time to play with MC.

Saludos,

Al

On 1/12/2010 12:21:24 PM, Al2000 wrote:
>On 1/10/2010 11:23:58 AM, jmG wrote:
>>You may think in term of the
>>surface plot operator.
>>Just as a conceptual approach
>>[hint].
>
>Thanks Jean, I already finished the damn
>function.
>
>
>
>Because I know now how to find the faces
>of the polyhedron, other options are
>available, as calculating the area,
>volume and center of mass. Also making a
>surface plot, but I still need to
>understand how is coded the data. I will
>study your attached sheet as well as an
>old sheet to draw a cube, but not yet.
>My Dec vacation already ended and I have
>few time to play with MC.
>
>Saludos,
>
>Al
___________________________

This stuff is above my head !
What about working with the adjacency matrix ?

Saludos.

Jean



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