class-A, class-B and class-C surfaces

class-A, class-B and class-C surfaces

Post by cycl » Thu, 31 Jan 2002 12:46:05



hi all,

any one can explain the different of class-A, class-B and class-C surfaces
to me?
and does Studio or Maya support to make these surfaces?

thanx advanced.

cycle

 
 
 

class-A, class-B and class-C surfaces

Post by Greg Tad » Fri, 01 Feb 2002 03:01:18



Quote:> hi all,

> any one can explain the different of class-A, class-B and class-C surfaces
> to me?
> and does Studio or Maya support to make these surfaces?

If I'm wrong, somebody please correct me, but basically the different
classes represent the "continuity." Continuity is the quality of transitions
from one surface to another. Class C has basic position, where the surfaces
merely meet up and share a common edge. Class B has tangency, in which the
surfaces have the same radius at the edge where they meet. Class A has
continuity, in which the surfaces not only have the same radius, but also
the same acceleration of change in the radii. You can think of class A being
the smoothest, class C being the roughest, and class B somewhere in the
middle. :D

You can't achieve complex class A surfaces in Maya, it doesn't have the
accuracy or the tools. Studio does.

Greg

 
 
 

class-A, class-B and class-C surfaces

Post by Mark Pritchar » Fri, 01 Feb 2002 08:23:48


This is quite interesting as we always hear these terms, yet I think the
terms are often misused, but no one has ever told me the definative
descriptions of each - these are what I think they are and I seem to get by
when using them in conversation with others !

I have (like everyone else) heard of "A Class" surfaces (or surfacing) which
I take as meaning production (generally automotive requirements) very good
quality surfacing with perfect highlight continuity etc....and I mean
"really good" - check out ICEM to show really good stuff (you thought alias
was good)

Never heard of "B Class"  or "C" Class  surfacing.

BUT the letters (A,B,C) when used like the following, to me, mean something
else.

"A" surfaces (don't confuse with A "Class" Surfacing)  usually mean the
outside surfaces of a form.

"B" surfaces usually mean the inside (wall thickness of plastic) of the form
- sometimes this includes all ancillary internal engineering detail.

and someone once told me "C" surfaces are those that would be created by a
sliding core or similar.

Now to test you all - and myself,

you could in theory have the B surfaces (inside wall thickness of plastic)
built to an A class quality ! (if you think people would look inside your
average power tool plastic moulding !)

Confused, I am,

Goodnight,

Mark

 
 
 

class-A, class-B and class-C surfaces

Post by Greg Tad » Fri, 01 Feb 2002 10:54:11


Quote:> I have (like everyone else) heard of "A Class" surfaces (or surfacing)
which
> I take as meaning production (generally automotive requirements) very good
> quality surfacing with perfect highlight continuity etc....and I mean
> "really good" - check out ICEM to show really good stuff (you thought
alias
> was good)

I don't know about ICEM Surf... I had the PTC guys give me a demo, and then
I took the surfaces they created and checked the continuity. Their so-called
experts created B class surfaces (tangency only)! Maybe their experts
weren't experts, but I was able to create better surfaces in Alias. And that
interface is awful IMHO. Don't want to start a flame war, those are just my
opinions.

Quote:> Never heard of "B Class"  or "C" Class  surfacing.

> BUT the letters (A,B,C) when used like the following, to me, mean
something
> else.

> "A" surfaces (don't confuse with A "Class" Surfacing)  usually mean the
> outside surfaces of a form.

> "B" surfaces usually mean the inside (wall thickness of plastic) of the
form
> - sometimes this includes all ancillary internal engineering detail.

> and someone once told me "C" surfaces are those that would be created by a
> sliding core or similar.

I've never had to work on the inside surfaces, just exterior, so those terms
are new to me. Thanks for the info though, it's always great to learn
something new. :D

G

 
 
 

class-A, class-B and class-C surfaces

Post by Matt » Fri, 01 Feb 2002 12:15:38


Its becoming an interesting debate of which software industry are going to
use in the future, Alias are improving there surface editing
tools/continuety while PTC ICEM are improving their interface and surface
creation.

Its seem common practice to create geomentry to near perfect condition in
Studio then get it Class A(perfect highlights, draft angles, G3+ etc)  in
ICEM and a growing number of companies look
like their only using ICEM, but i really couldnt get to grips with it, i can
create a whole model in alias in the time i can create a few surfaces in
icem.


Quote:> > I have (like everyone else) heard of "A Class" surfaces (or surfacing)
> which
> > I take as meaning production (generally automotive requirements) very
good
> > quality surfacing with perfect highlight continuity etc....and I mean
> > "really good" - check out ICEM to show really good stuff (you thought
> alias
> > was good)

> I don't know about ICEM Surf... I had the PTC guys give me a demo, and
then
> I took the surfaces they created and checked the continuity. Their
so-called
> experts created B class surfaces (tangency only)! Maybe their experts
> weren't experts, but I was able to create better surfaces in Alias. And
that
> interface is awful IMHO. Don't want to start a flame war, those are just
my
> opinions.

> > Never heard of "B Class"  or "C" Class  surfacing.

> > BUT the letters (A,B,C) when used like the following, to me, mean
> something
> > else.

> > "A" surfaces (don't confuse with A "Class" Surfacing)  usually mean the
> > outside surfaces of a form.

> > "B" surfaces usually mean the inside (wall thickness of plastic) of the
> form
> > - sometimes this includes all ancillary internal engineering detail.

> > and someone once told me "C" surfaces are those that would be created by
a
> > sliding core or similar.

> I've never had to work on the inside surfaces, just exterior, so those
terms
> are new to me. Thanks for the info though, it's always great to learn
> something new. :D

> G

 
 
 

class-A, class-B and class-C surfaces

Post by Greg Tad » Fri, 01 Feb 2002 15:01:41



Quote:> Its becoming an interesting debate of which software industry are going to
> use in the future, Alias are improving there surface editing
> tools/continuety while PTC ICEM are improving their interface and surface
> creation.

> Its seem common practice to create geomentry to near perfect condition in
> Studio then get it Class A(perfect highlights, draft angles, G3+ etc)  in
> ICEM and a growing number of companies look
> like their only using ICEM, but i really couldnt get to grips with it, i
can
> create a whole model in alias in the time i can create a few surfaces in
> icem.

I agree. Those ICEM guys sure are *, and while I'm sure that it's a
great program, I DON'T WANT TO BE THE GUY RUNNING IT. Ugh. I'd rather
subject myself to a life of writing RIB files by hand. ;)

G

 
 
 

class-A, class-B and class-C surfaces

Post by cycl » Sat, 02 Feb 2002 00:08:39


Thanks for reply.
so nice can hear back so many opinions, thanks :)
but does anybody here working for a AutoDesign Co.now? maybe can get a real
work flow of the surface making...
i am hearing...

cycle

 
 
 

class-A, class-B and class-C surfaces

Post by Mark Pritchar » Sun, 03 Feb 2002 20:50:20


Hi,

Working on some automotive stuff, and sat next to two guys using ICEM and
MCAD. We had created near perfect exterior surfs for car in Alias, but then
passed the data to the guy using MCAD. His job, all day, was to take a few
of my surfs at one time, and manipluate  them (using points that looked like
CV's) to create ultra smooth highlites. He literally spent one day on two
surfaces on the front wing.

My point is that although creating A-class surfaces sounds cool, in reality,
I wouldn't want to. I would want to be involved in concept -> initial
surface creation -> clay model CNC ready  standard. Then when the fun is
over, let these A-class guys do there CV tweaking.

What they do is amazing - I reimported the tweaked surfs into Alias and they
hadn't changed much, but the highlights were noticably  improved. We had
v.good highlights on the Alias model, but the MCAD tweaked had subtlties
that our model didn't, that could only be shown up by advanced evaluation.

If I said Alias may not be capable of creating these ultra high quality
surfaces then I would be shot. But imagine a front wheel arch (VW Golf
style) where the front arch main surface is swept round, and 'intersected'
with the front wing. At that intersection there is , simply put,  a soft
negative 'blend/rad'.

After you have built the main surfaces in Alias, built to the  interesction
point, you then draw curves etc to create that blend rad, putting on lots of
lead-in on the generation curves (sections) , so it couldn't be smoother (G3
- G4 etc). But becuse alias doesn't support those levels of continuity on
surface creation (only on curves) you sometimes get tiny  'shadow' when the
blending surf is put in. Two ways to get round this. Add more generation
curves when building, or tweak CV's manually after the surf has been built
(you lose history).

It is easy to see why you only go so far in Alias, then work into the surfs
using a higher-end package.

This of course is automotive, but for much product surfacing, you don't need
to be half as anal, so therefore you can use surfs built in Alias to
directly cut the tool.

Mark.

 
 
 

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