Weak in the basics of Open Geometry

I have imported a picture of a small shoe buckle in the jpg format
into an open sketch with Tools > Sketch Tools> Sketch Picture. I have
sketched an outline over the perimeter of the buckle picture using
circles, straight lines, and large radii via the three point arc tool,
with the intention of extrusion. Even though I was careful to snap
one arc to another on the red quadrant marks etc, I still have open
geometry which prevents me from extruding the sketch. I also do not
have smooth, blended transitions from arc to arc, due to snapping the
end of an arc to a quadrant of a circle, rather than being able to
snap it to "tangency".
Now this has been a constant source of exasperation for me, obviously
because I am weak in knowledge in this particular area. What I am
attempting to do is to use the "Add Relation" tool to select one arc,
CTRL select the adjoining arc, and make a tangent relationship,
hopefully joining the two ends (closing the geometry), and creating
blended smoothness between arcs at the same time. Well anyway I am
getting WICKED distortion of my geometry.
I have tried fully defining the sketch, which does indeed prevent the
distortion, but then throws me into shark infested "OVER DEFINED"
waters. Catch 22!
Please tell me 1- how do I close the geometry and get a positive snap
between lines, and 2- how do I create relationships without
distorting.
I really need to learn these principles of closing geometry because it
is beating me up something terrible in trying to learn surfaces as
well. I am prohibited from forming lofts, fills, etc.
If someone could help me in this terrible weakness of mine, I would be
most grateful.
Erika

 

Try not snapping it to the quadrant as this constrains it to just that
point. If you purposely snap it to the other curve at a location NOT
anything specific, you should then be able to add the tangent. If this
doesn't help, then send me your sketch so I can see what you are struggling
with.

WT

 

If you are trying to capture the outline of any kind of picture a
spline is probably going to give much better results.

TOP

 

Wayne and Paul gave you some good advice already. Another technique you
might try is using the tangent arc instead of the three point arc on your
second and later arcs.

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