Re: Wireframe Is An Essential Part Of The Process

I have used Solid Edge and I must say I really liked it. The mold design package in Solid Edge is like no other.

Mitch,

By wireframe he means 3d geometry with a line, arc or spline on every edge of every surface.

Mike

Cliff:

Mike C didn't say surfaces were synonymous with wireframe. He said, (paraphrased) that wireframes had lines, arcs or splines outlining the EDGES of the surfaces.

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Wireframe modeling

In CAD, a technique for representing 3D objects, in which all surfaces are visibly outlined in lines, including the opposite sides and all internal components that are normally hidden from view. Compared to surface and solid modeling, wireframe modeling is the least complex method for representing 3D images. ========================================================

-- BottleBob

No you don't.

Yes it is.

Cliff:

Why?

OK, let's try these:

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Definition for: wireframe modeling

A computer representation of a three-dimensional image by showing the outlines of all edges in a transparent drawing, as if the object was fashioned with wires. ==========================================================

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Wire-frame models, consist of lines and curves that define the edges of a three-dimensional entity. You can create a wire-frame model by drawing lines, arcs, polylines, and other two-dimensional entities anywhere in three-dimensional space. Wire-frame models have no surfaces; they always appear as outlines. Because you must individually draw and position each entity that makes up a wire-frame model, creating them can be exacting and time-consuming. ==========================================================

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3-D Wireframe Models

A wireframe model is a 3-D model created from one-dimensional lines in a three-dimensional space. It is a model with no actual surfaces or substance--it is merely an outline of an object. ==========================================================

Certainly sounds like wireframe objects are showing the edges/outlines of an object, as Mike suggested.

-- BottleBob

Jon:

I personally don't like that particular definition. While the statement is no doubt true, it doesn't actually define what wireframe geometry consists of.

-- BottleBob

Ok, for once, I'll tread into this shark-infested water. Michael Gibson, the creator of Rhino and of McNeel's earlier, facet-based modeler spent hours on the phone explaining this one to me some years ago, when I was going nuts trying to figure out why programs that were supposed to create surfaces from wireframes didn't see anything when I imported my Vellum wireframes into them (Vellum originally was a wireframe-only modeler).

The terminology escapes my memory but it's something like this, which old-time users of AutoCAD probably will recognize and clear up. There are wireframes and there are wireframes...

True wireframes, the simple ones that are only definitions of lines, can't be directly surfaced. In order to create a surface on them you either need to turn them into closed entities (such as facets: triangles or polygons) or they need to be surface entities to begin with, with directions defined perpendicular to the line entities. I forget how this part works, but I remember that some program (maybe a later version of Vellum) would display little arrows perpendicular to the lines, showing the direction of the surface.

So a wireframe model intended for surfacing requires more information than just the line entities themselves. The "wireframe" mode of some surfacing modelers provides this added information. I believe that AutoCAD did as an option, from day one of its involvement with 3D. CadKey may have; I do remember surfacing some of their "wireframes." But CadKey Lite did not, IIRC. It only produced plain wireframes, like Vellum originally did, and you could not surface them.

There were programs that would take a plain wireframe and let you attach surfacing information to them, more-or-less manually. I recall doing that with an interim version of Vellum, and sometimes your surface would come out looking like a Klein bottle. You had to get all of the surfacing directions right, and it was easy to make a mistake.

A program that integrates wireframe with surfacing, as I understand it, generally attaches the surface information to the wireframe as you draw.

If you want to see how it was (is?) handled with polygons, look at the ASCII file output from AutoCAD, at least from around v.13 or so, which is the last time I looked. A 3D entity made from wireframe lines didn't define the polygons as entities, only as lines with endpoints -- which may correspond to other endpoints, but which still did not define the entities as polygons. When they're polygons, the ASCII file tells you so. Then they can be surfaced -- not with NURBS surfaces, but with facets, like the ones that generally are used for rendering.

I'll now go back to sleep on this subject.

-- Ed Huntress

You are correct, Cliff!! I can not believe all the false information which was referenced here!?!?! Only a few of the writers got it right and most got it wrong! Also, (sorry most of you were wrong) by people who supposedly use or have used wireframe modelers!?!?!

I worked with and designed in wireframe modelers and there were NO surfaces and NO Solids involved.

As wireframe modelers added graphical representations (not surface or solid data) and surfaces and solids, people changed or lost the meaning due to "graphical" display modes and workflow demands per modeler. Tools like CadKey did some interesting translations of wireframe data into surface data, that's where I think some people think wireframe exist or are the same due to surface/solid data share in that environment (which again, originally came from the wireframe data)?

Most all modelers today can extract, use or share the edge or tangent edge data from surface/solid data or the edges are "displayed" as wireframe (just graphical display data) but that is NOT what the original wireframe meaning or use originated from.

A wireframe modeler has curve and point data in 2d and 3d space, nothing else. Beyond that, more sophisticated wireframe modelers could solve intersections for a resulting curve or curves or points.. or interpolate wires (like a loft/sweep) and also, be good at translating volume... but again, there were no surfaces or solids involved. Later, some had graphical representations for the wireframe boundaries (which looked like surface/solid data) but again, it was not surface or solid data (just for looks and show).

So, there is "Wireframe" data and "wireframe display" data. Wireframe display can be graphical representations from the edges of your surface or solid data or the display of wireframe data, the display data is visual only. To get true wireframe data, (associative or non-associative) you would have to extract the edge/intersection/tangent from the surface/solid.

So, as wireframe evolved, yes, surface/solid data can also be shared or derive to/from wireframe data or extracted to become new wireframe data and/or be reused again, or create wireframe (the old way) without surfaces or solids... associative or non-associative...

BTW, I can create a design in SolidWorks or Pro/e today using the old wireframe method, NO surfaces or solids. (it would not be fun though) And yes, I can then create surfaces and solids from that wireframe data.

Anyhow, interesting how interpretations, meanings or use evolve over time... especially the cad world.

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Cliff wrote:

Cliff:

This seems to be yet another case of semantics over substance. The OP was saying that wireframe entities were outlines. Whether there were surfaces between the outlines seemed irrelevant to his point.

I'm sure that virtually everyone that has extracted edge geometry from a solid or surface model with a CAM system to generate toolpaths realizes that.

*Alone*? I don't recall that word being mentioned by anyone. If an outline of the part is overlaid on (or extracted from), the surface or solid model, the model can then have a wireframe component.

Wireframe = Outline data. Seemed pretty straightforward to me.

-- BottleBob

No, it's not outline data, BB. As Cliff said, and Paul said, and I said, a wireframe doesn't relate to edges or outlines of anything. It MAY represent edges, and it can be EXTRACTED from edges, but the wireframe itself is just a collection of lines.

You can make a wireframe model in which the wires cross the middle of a plane, in which case they don't relate to any edges. And, in complex 3D curves, wireframe models often have wires laid at regular intervals across the curve. Ships' hulls are modeled that way, for example, both in manual drafting and in wireframe representations.

If your wireframe is extracted from a solid or 3D surfaced model, then the wires you extract from the model probably are going to be the intersections and edges. But not necessarily so.

A wireframe model doesn't have to relate to edges or intersections in any way. All you can assume about it is that the lines lay somewhere on the surface of the model.

-- Ed Huntress

Yes, from Cliffs and my point of view there is a difference from the origin of wireframe design/modelers which came before the modelers we use today. Kind of a chicken and the egg thing?

For me, wireframe is the original construction of 2D/3D entities and/or the assoc/non-assoc reference to the surface/solid body(s). So, yes, when the outline of a surface/solid edges are extracted, those edges then become wireframe data.

There is a semantics problem here because of the context of the interpretations (such as visual). Todays use of 2d/3d wireframe data request tend to be a need connected with CAM. And that need is to extract or derived edge data is used in some CAM programs (from what I understand related to some programs workflow, tool path needs, layer management,..?)?

Going back to the original subject though, wireframe extraction and sharing is used with most of todays surface/solid modelers and some basic 2d/3d wireframe support is fairly common. Having 2d/3d assoc/non-assoc wireframe (or splines with c2 > support) capabilities along with the surface/solids and wireframe shared data, enhance the workflow of building more complex models and assemblies.

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BottleBob wrote:

Ed:

It seems there are too many exceptions to make any systematic generalizations about wireframe geometry. Oh well, I tried.

-- BottleBob

Maybe it's just easier to say,...

Surface/solid data by themselves do not wireframes. Surface/solid edge representation is not wireframe data.

And, wireframe data can be extracted from surface/solid data.

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BottleBob wrote:

Paul:

The different perspectives on this wireframe issue are interesting. I use a CAM system to extract edge and tangency data from solid models for the generation of toolpaths on a regular basis. As well as create simple solid models for ease of CNC 3D profiling of parts or sections of parts. So those perspectives (machining related) are the ones I bring to this discussion. But I can now see that those are only just a couple of interpretations out of a number of others that I've not fully considered until now. IMO, this is one of the rare FEW threads crossposted to comp.cad.solidworks that has been actually productive in knowledge exchange.

-- BottleBob

I also come at this from a machining viewpiont. Sometimes I want a surface, but other times I would rather have the edge data to toolpath. I didn't realize that the wireframe entity was more than just a collection of edges. This is why I read these groups.

Mike

Cliff:

So you're claiming that a single line is a wireframe? In 3D space? LOL

Well then, by all means, define wireframe.

-- BottleBob

Cliff:

Are you trying to resort to clever witticisms and barbs to avoid answering the question? Is a single line in one plane considered a wireframe in 3D space? Yes, or No?

You claimed that "wireframe" was "rather well defined". I then asked you to define it. You haven't done so. I submit that if this thread has indicated anything at all, it's that "wireframe" is VERY ill-defined, which would make your claim at best misleading, and worst simply false.

So please by all means, support your claim by defining "wireframe".

-- BottleBob

"Wireframe" "Wire frame".

HTH

Cliff:

You claimed wireframe was "rather well defined", so define it.

-- BottleBob