Problem constraining spline

[jeffescott]

I have a spline with constrained points.  Each end is at a constrained point.  I have created parallel constraints on the each end curve handles and the middle curve handle.  Each of these is parallel to the x axis.

The remaining two curve handles are constrained by the distance parallel to the curve handle to the x axis.

The spline is still not shown as constrained.  

What else do I need to constrain

[jeffescott]

oops here is the 3fd

[wersy · Accepted solution]

The handles must also be determined in the angular position and length.
Although I added the missing dimensions, the spline remains blue.
I can't say why, but sometimes the spline still doesn't turn black.

[g-andresen]

Hi,

With fit point spline you need 4 determinations per control point (2 distances for the point and 2 for the tangent*).
For control point splines the coordinates of the control point are sufficient.

Screencast

günther

* aligned lenght & vert  or  hor lenght    or    angle & 1 lenght

[jeff_strater · Accepted solution]

@jeffescott - thanks for the design - that always helps.

This is just my personal opinion, but I think that it is not always necessary to fully constrain a 2D spline.  That said, if you want to do it, it can be done, but is painful.  You have to fully constrain all the handles as well as the fit points, including the handle endpoints.  If you want to fully constrain your sketch, I would just "fix" the spline and the handles.  There is a trick to that - a text command called "sketch.showunderconstrained" will select all the underconstrained geometry in the sketch.  Then, just choose "Fix" from the constraint toolbar.  Fix is nice, because if you ever need to adjust the spline, just "Unfix" it, edit it, and "Fix" it again.

[jeffescott]

Thx its black   had a a couple of constraints that i must have deleted along the way.  Added the handle lengths and constraints equal 5x4=20

[g-andresen]

Hi,

Try it using Control Point Splines!

günther

[jeffescott]

I will try them out.   I think i will have to interate to get the points.  Since that is how i know to get the right shape.

the next steps are to draw a turn on a flat slope (in f360).  Then match the ski edge to the turn.  The ski will be flexed and angled. Then straighten out the ski.   This will set side profile….  Right now i just set up three nails and the pull the side together a bit in the between the two points and viola.   Gonna be a while to get it sorted out in my head