use the command InterpCrv… via menus, it’s Curve > Free Form > Interpolate Points
before clicking the first point, look at the command dialog and you’ll see the option ‘start tangent’… click that (or press the letter S then spacebar… (since the letter S is underlined in the dialog… ‘S’ works as the keyboard equivalent to mouse clicking the button)
click the first point… you then tell it which direction the start tangent should go in… (in your example, set direction to the left of your horizontal lines…)
click the middle point
look in the dialog again and you’ll see the option ‘End tangent’… click that or press E then spacebar.
Hi Jim - the desired tangent direction, if I see what you’re doing, is horizontal, parallel to X; it looks like you’ve set it vertical. (use the Direction option to override the automatic choice of that vertical curve to set the tangent direction)
Through trial and error, I found that if I click the DIRECTION button then click to the LEFT of the starting point and do the same but click to the RIGHT of the ending point I wind up with the correct result.
If I do RIGHT/RIGHT or LEFT/LEFT I get screwed up stuff.
fwiw, if you hide/delete/lock/move the vertical line, things will go a little bit smoother since it will know to go along the vector tangent to curve at the picked point… you won’t have to explicitly change the direction via the Direction button.
in the latest group of pictures you posted, it shows that the vertical line was picked for your tangent point but you want the horizontal one… there are two curves at the intersection and it doesn’t really know which one you want… if you get rid of the vertical line, there won’t be an intersecting line at your pick point and the correct (only) curve will be chosen.
You can’t. It’s inherent to NURBS control point/CV modification. When you are moving a CP, you are changing the invariant of projective transformation, but not the topology in the projective plane. You can either 1. have a curve go through points (EPs) having to accept the projective plane or 2. assume a form (CPs) having to accept the points the curve intersects. Both are mutually exclusive mathematically.
You can if you have a curve with 2 more control points than the number of specific points you want the curve to pass through. Place an edit point at each specific point keeping the edit points next to the ends free. Then move the edit points adjacent to the ends as needed for the desired slope and shape at each end. The control points will wind up where they need to be for the curve to go through the specific points with the slope at the end…
One method is to create a curve with the required number of control points, and then drag individual edit points to the specific points. Then move the edit points adjacent to the end points as desired.
An alternative is to locate an additional point between each end and the adjacent specific point you want the curve to pass through. Then create the curve using CurveThroughPt or InterpCrv with the specific points plus the two additional points. Knots=Chord or Knots=SqrtChord may work better than Knots=Uniform.
Be aware that moving an edit point will alter the entire curve except the curve will continue to pass through all the edit points. Oscillations can be a problem.