Surface Geometry at the Ground Floor

Can anyone lead me to either literature or tutorials on the real
rudiments of surface Geometry? I do not posess the know-how yet to
get very much from the ones that I know are available, namely the
Classic presentations from the Di Monte Group, which I am sure are
Golden, and also the Magical Mr Lombard's words as well. In truth, I
am in need of learning real basic principles of surface geometry, in
order for me to proceed to the next level. I have found that despite
what some people keep telling me that, "anything that can be done can
be done using Solids", may or may not have some truth to it, however I
feel that knowing two ways to do something has to be better than
knowing one. It simply has to make life easier for the draftsperson to
have more weapons at his/her command, so to speak. It is for this
reason that I would like to learn Surfaces starting at the real ground
floor rudiments.

I will appreciate any help, that anyone would offer,
Amy

 

"anything that can be done can
be done using Solids"

Anyone who says that hasn't really done all that much.

 

The rudiments are simple once you really look at what solid and
surface features do

To begin with, Solid features ARE surface features, except:
A) Solid features ALWAYS make a completely enclosed volume (which you
can see in the preview for a cut, or if you deselect 'merge result'
when making a boss then go to the solid bodies folder and hide the
other bodies), while surface features are not limited by that
constraint
B) Solid features know which side of the faces it creates makes
'stuff', and which side makes 'void'. A surface sitting in space on
its own, even if it does describe a completely enclosed volume, has no
definition as to which side is 'stuff' and which side is 'void'. Is
that surface a cylinder, or is it a drilled hole? It doesn't know
until you tell it using 'thicken' or 'cut with surface'

I find it impossible to get caught in this rut about solid features vs
surface features, and simply put it out of my mind years ago. They
are different, yes, but only in execution. At the end of the day they
both make the same thing - faces.

When it comes to modeling, the only thing that matters is faces.
Repeat that to yourself - the only thing that matters is faces. When
your product is being made on the shop floor, or when it is on a shelf/
delivered to a customer, the only thing that ever mattered was the
faces of the object. That's what we do with our CAD - make faces. And
our deliverables don't care how those faces were made.

Solid features make faces, but they always (well, almost always -
there are spheres) have to make a few extra faces in order to follow
the rule of delivering a completely enclosed volume. Which can be
hard to visualize in the case of a cut... that's why I say look at the
preview and you can see how a volume is made when you execute a cut,
before it is subtracted behind the scenes from the
'workpiece' (otherwise known as that existing chunk of 'stuff' on
your screen).

Surface features don't have that limit - you can make one or several
faces at a time, then trim or knit those faces together to make the
final model.

If you have the time, try to make a simple model one face at a time,
using surfaces, to see how it works. Its horribly inefficient on
simple cases (making a cube one face at a time requires 8 features,
for instance - 6 planar surfaces, a knit, then a thicken enclosed
volume), but you will learn how it works. That is what every 'solid'
feature you have ever made does behind the scenes - solids are
'macros' for the tedious work of making things one face at a time out
of surfaces.

But there are times when making model geometry one face at a time DOES
make sense, and catapults you past problems that you run into when
having to deal with that 'fully enclosed volume' restriction of solid
features. There are samples on the Dimontegroup web site that talk
about some of those problems, but apparently not clearly enough. Sorry
'bout that - I tried. As soon as I figure out how to rewrite the damn
site there will be one more tutorial from this years SWx World that
has (I hope) some of the clearest samples I have ever done talking
about 'making faces'.

It's good to have surfacing knowledge in your magic bag of trix
because there are times when doing things 'one face at a time' (or
more probably, several faces at a time, just not as a completely
enclosed volumes) with surfaces actually is wayyyy more efficient.
Super mega wayyy more efficient.

And a lot of times, its the only way to get to the finish line - I
have been using SWx for nine years, and I would gladly bow down,
grovel, and wash the feet of the person who really can deliver on the
statement that 'anything that can be done can be done in solids'.

A 'hybrid' approach (that is stupid slang for mixing surfaces and
solids) is, in my experience and the experience of many others, the
most appropriate way to go on certain projects. But again, bringing
back to earlier in the post, I don't even think of its as a 'hybrid'
approach because both surfaces and solids just make faces - if you
pick features based on their ability to make the faces you need the
most efficient way, there is no switching from one modeling
environment to another. SWx is just one big 'making faces' tool. Cuts
and bosses both make faces in different ways and we don't think of
THAT as a 'hybrid' thing - why should we apply an arbitrary division
to solids and surfaces?.

I hope this helped - I do not envy you for having to learn this stuff
from the ground up. I am learning new software right now and am newly
reminded how horrible it is to get straight, useful answers on
fundamental issues that most people using the software have already
come to terms with. Keep asking the questions, Amy, until you get an
answer framed in a way that makes the breakthrough for you.

Ed

 

Thanks for the tip.

 

Mr Eaton,
After having both spoken to many members of this newsgroup
personally, and intently watching what the acknowledged Solidworks
Guru's of this Forum have to say, ( and it is obvious even to the
unskilled, that there are several very fine ones here), with utmost
reverence and respect, for both you and your Firm, it is more than
obvious that your personal skills are the yardstick by which most here
are measured. You Sir, are a Guru's Guru, far and away, and I am
extremely flattered and grateful that you took the time to respond to
my humble plea. The last paragraph of your reply, tells me that you
know exactly what many of us are going through, with regard to
learning surfaces, and you hit the nail right on the head, so to
speak. Thank you sir.

With gratitude,
Amy Labritto

 

Dang, now his head really is going to get bigger! )) (I have always
agreed, though...)

WT

 

You're absolutely right in your praise. We all owe more than we can possibly
repay to Ed. Try starting out with his SWW 2005 tutorial called "Surfacing
for Blockheads".

Jerry Steiger
Tripod Data Systems
"take the garbage out, dear"