Curvature control vs Curvature tangency

.....and the million dollar answer is.....(ie on a spline what is the
difference between how it control the look of it?)

 

As I understand it, curvature control let you specify the curvature along
your spline while curvature tangency is a constraint that ensures the
curvature at the end of the spline matches the curvature of the other curve
at the connection point (called C2-continuity, vsible with zebra stripes)
Did I win the million ?

 

Sorta. In normal unflavored parlance G1 (tangency) means
there is not a sharp edge at the common edge shared by two
surfaces (or the common point if it's two curves). G2
(curvature continuity) means that the curvature of both
objects is the same at the intersection. (I'd guess that
if something says "curvature control" it means mid curve.
"Curvature tangency" sounds like something a gearhead
would dream up.)

See
http://discussion.autodesk.com/thread.jspa?messageID=3903889

or just go straight to

http://discussion.autodesk.com/servlet/JiveServlet/download/
75-339487-3910843-33066/g3.jpg

(unwrap the url) for a screen shot comparing curve end
conditions.

========================

As I understand it, curvature control let you specify the
curvature along
your spline while curvature tangency is a constraint that
ensures the
curvature at the end of the spline matches the curvature of
the other curve
at the connection point (called C2-continuity, vsible with
zebra stripes)
Did I win the million ?

 

:
".... But what do those two words together mean?"

Nothing. Don't know where it came from (Solidworks or
Arthur?). My guess is the intended meaning is "curvature
continuity".

 

See http://me.queensu.ca/courses/MECH466/class27.htm ....

Yeah, but what does it *look* like? 8~)

 

Curvature might actually be 3D ... in all directions at once ...
<G>.

Now, that's a novel idea. 8~)
Does prompt a question.... is the new spline stuff 3D or 2D?

 

In SW 05, you can make splines tangent or curvature continuous to other
geometry. If an spline is tangent to a 5 in rad arc, the instantaneous
curvature at the end of the spline could be anything, but if it is c2, the
instantaneous radius will start at 5 and change smoothly from there.
(Curvature is defined as 1/radius).

The "curvature control" on a c2 spline is a symbol that looks like a
foreshortened radius dimension. Dragging it makes the spline either
maintain or change the rate of change of the curvature at that end.
Basically, it makes the spline stiffer, or gives the initial curvature
value more influence over the spline.

matt




(Arthur Y-S) wrote in

 

That's what I'm asking... can SW create a spline curvature continuous to a helix
(or any other 3D curve) or is it limited to 2D curves?

 

For whatever reason, you can't make the 3D spline c2 to the helix directly,
but you can use convert entities on the helix to make it into a spline in
the 3D sketch and make the c2 relation between the original spline and the
converted helix.

matt

 

Ok, that might need some clarification. When you do that in the 3D sketch,
you do not get the curvature control handle (foreshortened radius symbol),
and the curvature combs don't look to be continuous at all. So the c2
sketch relationship can be applied, and it is listed in the relations box,
but it doesn't seem to have any effect.

matt

 

Thanks, Matt.

It might be understandable that the comb wouldn't look continuous. Calculating
derivitives beyond the second are required to get what most of us would
initially expect to see. Basically, I was just curious as to whether the
controls were available for 3D as well as 2D (planar sketch / section) entities.

 

I took that course about seven years ago.