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# Spline sketching problem.

mor
Member Posts:

**9**PROWhen trying to constrain a spline somewhere along its middle
(such as: pass through a point, or even worse – also tangent to, say, a
horizontal line through that point) - I find myself fighting a disturbing dependency
between the two spline's end curves guides.

How can I free that dependency?

Thank you

Avshalom.

0

## Answers

379✭✭✭Also you can constrain the spline by using "fix" constrain.

9PROthe problem is that before you constrain the ends guides, when you constrain the spline by attaching it to a point or line (say Tangent constraint) somewhere on the spline line -

both ends guides "gain" some inter-depended relations between themthat seriously limit your freedom of shaping the spline.I will try to explain in other words: After I entered the point/line tangent constraint to the spline, each time I try to move one guide - the other guide moves too; Also - the guide I'm trying to move happens to be (heavily) constrained in some way by some relations to that other guide.

Sorry I couldn't upload a simple sketch example here.

379✭✭✭In this video all spline points are constrained except guide point.after applying tangent constrain one guide line moves only in horizontal to the line/edge.It is to maintain the tangent between the line and that end point of spline.

But i didn't find any dependency between two guide curves(tangent lines of spline).

I apologize if i m explaining something different than you.

9PROIt seems to me that the case you show doesn't apply to my problem.

Please try the following:

1.draw: a rectangle. a point within it (somewhere near the center). a horizontal line attached to the point. make them all fixed.

2. draw a spline from lower left corner to the upper right corner. now attach the spline to the point. try to make a few curved lines options from the spline.

3. make the spline tangent to the horizontal line. try again to make different curves from the spline.

If you do not encounter any problem - please let me see how you do that (like your example above).

379✭✭✭Since the the spline is tangent to the line at the end point,guide point are not allowed to move in some region where the tangent will not be there.

In spline you have only two curves(only one point in spline other than end points). Both curves are trying to maintain tangent on one end with end point of horizontal line.so while moving one guide point it changes the shape of a curve and to maintain tangency the other curves also moves accordingly.You can reduce the dependency by adding more point on the curve.

To keep other point fixed you can add fix constrain to that point

9PROBut look - In this case I can make both lines' ends tangent to the horizontal line point and still move freely at each end.

may be there should be some way to change OnShape spline's logic?

Using spline in the above cases is actually useless.