Is SolidWorks really a solid modeler?

Well, not really. The surface normals vary from place to place on any decent surface. But the (and this is a major diff) surface normals for a surface can be reversed just by reordering the knot points.

IE, Given a surface of M X N knot points the surface S(1..M,1...N) is the same as the surface S(M...1,1...N) or S(1...M,N...1) except that the surface normals in the case of the later two are reversed. The surface S(M...1,N...1) has the same normals as the first surface.

Actually, there seem to be tow things called "surface normals" as they relate to surfaces. One applies to each point on a surface and are actual normals (vectors). The other is just "which side is which" which is what the above is about IIRC (clearly the magnitude of vector normals would differ from one side tothe other, right?)

"Out", decided by the kernel.

I kept asking jb what it looked like from the inside of a solid ..... was it dark?

Nice! I'm jealous... I didn't think about extruding one pentagon and cutting from the opposite side, with 'flip side to cut' active. Very well done!

-Ed

Anyone know what a Cranfield Object is? Anyone know if SW can model such? As an "exact" solid object, not surface patch kludge?

So it is macro-able and hence a candidate for a solid feature ala polygons in the sketcher?

I am having a hard time figuring out how you did it with only two extrudes. Guess I'll have to go to CS301 to find out.

"Edward T Eaton" wrote in news: snipped-for-privacy@uni-berlin.de:

Thanks. Pehaps I should start a series at SWW. Uh, maybe not.

I didn't do it with JUST two extrudes - that was Dale. I did two solid extrudes and two delete faces - Dale did an extrude solid then an extrude cut.

Just to be sure we are talking about the same thing:

Ed and/or Dale, Could you please publicly post your models so the rest of us mortals could be enlightened?

I don't have the capacity (or maybe just knowhow) to post my model. It's pretty simple really. First, I made a layout sketch that determines the size of the dodo and gives me the angle between faces. The first extrude is a pentagon profile the full height of the dodo. The extrude is drafted outward at the faces angle. The second extrude is a cut through from the opposite side with the same draft option, with the cut direction flipped.

A DRAFT!!!! Duh. And this whole time I was trying straight extrudes.

Ed showed me what he did. And he is entitled to another box of donuts. OOOO I can put it up on my site (with appropriate attributions) if it is OK with Ed.

See below,

I agree that 3D sketcher needs equal relations. But I was able to make the tetrahedron in a 3D skecth without equal relations. Mate points to planes.

The focus IS on the end user. Its just that they are for the majority of end users. When they made the first (fill-in-blank with any high tech thing, a car, a computer, a calculator, etc) did all these devices have all the functionality when they came out as a new product? Of course not! My first calculator only could add, subtract, multiply and divide. But that fit a large percentage of people that first bought them. Then as they went along, more features were added to suite the majority of what endusers needed or wanted.

The same is with SolidWorks. I'll bet you that there are few enhancement requests for dodo creators...

Dan

Whoa Dan, I'm not trying to bash, I'm trying to stretch, I'm trying to get to fundamentals; things that will benefit all users. The title of the thread may be a bit provacative, but I use the word solid with a very special meaning refering to regular solids (or platonic solids). And that question came up because I was reading a book on Computer Aided Graphics written in a decidely CAD neutral viewpoint.

One thing I found that was very neat about Ed Eaton's construction was that with the same two features you can get to an icosahedron. Now that is cool. I suspect Dale's construction can do the same thing. I'd sure like to see what you came up with too. So far there are three approaches:

1. Two (or more) intersecting extrudes. a. Stable and quick b. Requires some knowledge of geometry and constructions.
2. Mated planar surfaces (seems to cause SW problems.) a. Assy. needs to deal better with overconstrained mates b. Seems to be some stability problems that need addressing.
3. 3D Sketcher (with a lot of hoops to jump through.) a. 3D sketcher needs an equal relation b. 3D sketcher needs a coplanar relation

Now I guess I would qualify as an end user since I sit in front of a tube doing SW, Nastran, Cosmos for more hours in the day than I care to think about. And then I'm crazy enough to want to teach the same subject in the evening. But I think we need a bill of rights to protect the minority end users from the majority some times. comp.cad.solidworks is the next best thing to that.

I think the Dodo is an apt illustration. God created the Dodo for a good reason and the majority helped the Dodo evolve to extinction. See:

Got foorp?

Its fine by me. Give proper credit to Dale Dunn, though... he figured out how to do it in two features (my first crack at it had four)

Ironically, I can't think of a way to do it with two extrudes and face deletions as Ed describes.

"Edward T Eaton" wrote in news: snipped-for-privacy@uni-berlin.de:

LOL!

At least you have a sense of humor!

Dan