geodesics

Hi,

Can Solidworks (or any CAD program) place a curve onto a surface such
that it is the shortest length between two points on the surface?

Thanks
MT

 

Only in special cases.

One problem is that the solution can have more than one answer on a
curved surface. SW doesn't like ambiguous.

 

I'll give it an unqualified "I think" it can be done given the right set of
circumstances. Perhaps you can be a little more specific? Your use of the
word "goedesics" conjures up images, but.......

 

Read some of Einstein's works for a simple explanation.

On a sketch plane a line between two points is a geodesic.

 

I have a complex surface (not a simple sphere) and two points on the
surface. I'd like to connect them with a curve that lies on that
surface so that the length of the curve is the shortest possible. A
curve thru reference points simply draws a line from A to B but not on
the surface. I know that projection may be needed but don't know how
to assure myself its the shortest curve length. Although there can be
an infinite number of solutions for some cases, I believe that in my
cases there is only one. How/Can I find it without a lot of
manipulation of the model?

Thanks
MT

 

Back to my first response. Not with SW. If you have a mathematical
definition of the surface you might find it.

 

I honestly don't know anything about the subject (just find it to be an
interesting question). You might try doing a web search. I did a quick
search (their server is very slow this morning and I'm a little pressed for
time right now) of Rhino's site and found

http://news2.mcneel.com/scripts/dnewsweb.exe?cmd=article&group=rhino&item=1
73295&utag=

looked like it was promising, but don't have time to follow up on it.

http://news2.mcneel.com/scripts/dnewsweb.exe?cmd=article&group=rhino&item=6
6792&utag=

.... the comment on mesh alogrithms was interesting.

Good luck with it.

 

For a sphere, if you create a sketch plane using the two points on the
surface and the center of the sphere, the intersection curve of the
sphere and sketch plane will be the shortest curve between those two
points.
This will not necessarily be true for a non-spherical surface.

 

What kind of precision would be required of your final curve?

 

Maybe I dont totally understand here.

If you have a noplanar surface with alot of topology and you are trying
create a curve that follows the contour of the surface?

Heres what I would do

1. Create the intial surface
2. Create a new sketch with the location of the 2 points and draw a line
connecting them
3. Extrude the line so it intersects the first surface
4. using your sketch tools, use the intersection curve to create the
curve with the intersection of the 2 surfaces
5. You will have a 3d sketch that contains it.

If I am totally offbase here, disregard this message ;-)

FWIW,

Mike Lamora

 

Shortest distance between two points while staying on the surface. It
is not necessarily a straight line projected.

 

What's wrong with the "sketch on surface"? If you draw a 2 point spline on
a surface, it should connect the points with the shortest path. It seems
like the simplest solution, or have I missed something?

matt

 

Just to clarify, in 3D sketch there is a function called Spline on Surface.
This is new with sw05.

 

It appears to create a curve that takes the shortest path sometimes. It
is subject to singularities or forbbiden zones and when near them will
act funny. I will try to post some of the pathology later.

 

Two examples posted on the SW forum under Sketching with the title
Geodesics.

 

Haven't seen the capability in Solidworks for geodesoics that say Catia has,
in Catia you can even make a constant offset to a curve on a surface. as
well as the shortest connection between 2 points on a surface.