Extracting frame lines from 3D mesh or object

[Mugna101]

Hello people!

Im using autocad 2018.

I need to extract the frame lines from 3d meshes (i think its called a mesh but im not sure)

I have attached an example file.

 

Is there a way to automatically extract the outer lines so i could erase the rest and be left with only its frame?

If there isnt any automatic way, how can i do it with the least amount of effort? its really hard to use a 3d poly and manualy frame itScan 3 (1).rar

[ammobake]

When you say frame lines it could mean one of 2 things.

 

Do you mean the lines that were used for both ends that were used for mesh creation, originally?

Or do you mean the "ribs" along the mesh?

 

In the case of meshes, the number of surface tabulations determines the number of "ribs" if that makes sense.  So if you were to draw two arcs and draw a mesh between them with 4 surface tabulations, you would end up with a jagged mesh with 4 "faces" if you will.

 

If you are wanting to extract the source lines that were used to create the mesh (at both ends) an option is to use 3DPOLY command and "trace" out the ends of the mesh with a 3d polyline.  Only it won't be true to the original source geometry - it will just be as accurate as the surface tabulations suggest (if that makes sense) since you would be clicking to each node at the ends of the mesh. 

 

However, you can improvise.  If you know the ends are curved you can trace the ends out as a spline and get pretty close to the original source geometry.

 

If you are wanting to create additional linework along the periphery of the mesh you can trace along the ribs with a polyline or 3dpolyline depending on whether or not those lines are coplanar.

 

There may be a lisp that can explode the mesh, then convert or otherwise replace the 3d faces to 3dpolylines, automatically.

 

If the lines of the mesh are all you want to print, you can do this with a viewport without having to draw all this.

 

You would just need to set up the view either using 3d orbit in the viewport or use one of the standard isometric views.

While you are clicked into the viewport you can then change the "Visual Style" to 3d wireframe (or use the 3d wireframe option in the plot settings).

 

This way it doesn't print the mesh surface just the linear geometry.

[Mugna101]

9 hours ago, ammobake said:

When you say frame lines it could mean one of 2 things.

 

Do you mean the lines that were used for both ends that were used for mesh creation, originally?

Or do you mean the "ribs" along the mesh?

 

In the case of meshes, the number of surface tabulations determines the number of "ribs" if that makes sense.  So if you were to draw two arcs and draw a mesh between them with 4 surface tabulations, you would end up with a jagged mesh with 4 "faces" if you will.

 

If you are wanting to extract the source lines that were used to create the mesh (at both ends) an option is to use 3DPOLY command and "trace" out the ends of the mesh with a 3d polyline.  Only it won't be true to the original source geometry - it will just be as accurate as the surface tabulations suggest (if that makes sense) since you would be clicking to each node at the ends of the mesh. 

 

However, you can improvise.  If you know the ends are curved you can trace the ends out as a spline and get pretty close to the original source geometry.

 

If you are wanting to create additional linework along the periphery of the mesh you can trace along the ribs with a polyline or 3dpolyline depending on whether or not those lines are coplanar.

 

There may be a lisp that can explode the mesh, then convert or otherwise replace the 3d faces to 3dpolylines, automatically.

 

If the lines of the mesh are all you want to print, you can do this with a viewport without having to draw all this.

 

You would just need to set up the view either using 3d orbit in the viewport or use one of the standard isometric views.

While you are clicked into the viewport you can then change the "Visual Style" to 3d wireframe (or use the 3d wireframe option in the plot settings).

 

This way it doesn't print the mesh surface just the linear geometry.

Thx for the reply!

 

What I need out of these meshes is simply the outer lines, corners and connection between those. all the mesh triangles in between these corners are not needed.

What i do now is use viewports in the model area so i could see which vertex ive picked in a 3d area and a 3dpoly to line them up manually.

 

Do you know of a lisp that could work? ive tried Lee Mac's convex hull before but i didnt get it to work for some reason. really not sure why..

is there any other lisp you can think of? you think convexhull would work for that? if so ill keep trying