curve edit points

 From:  Michael Gibson
3398.2 In reply to 3398.1 
Hi Luis, it sounds like you are looking for a way to edit a curve by moving points that the curve passes through?

There is not really any edit tool for that in MoI currently, if you have some situation where you want to force the curve to pass through some same number of points all the time you will probably need to delete the curve and then draw a new one with Draw curve > Freeform > Through points.

Like you saw, you can manipulate a single point on the curve to force it through another area by dragging directly on the curve when control points are turned on, but that may not help you if you want to maintain a whole sequence of constrain points instead of just one. That mechanism is kind of more intended to be a general curve shaping helper mechanism.

1. Is there a way to create a snap point on a curve at the intersection (and/or projected intersection?) with another a curve or line?

Yeah, if you are drawing new objects, those kinds of snap points will show up on other existing curves automatically, unless you have disabled Object Snap, or disabled Intersection snap specifically, or turned off the option under Options dialog > Snaps > Object snap options > "Use apparent intersections".

But what you may be running into is when you are dragging an object's control points to edit it, it will not snap on to various things that involve itself. That's to avoid a kind of over-snapping problem that can otherwise easily happen. If a curve snapped on to its own self when you were dragging points, it tends to kind of lock things up with snaps and prevent freedom of movement of the points which is bad when you are focused more on trying to adjust the general look and shape of the curve when moving the points around.

So if it is that issue that you're running into - (no self snapping when dragging), you may need to do something like draw an individual Point object (Under Draw curve > More) and then use it as a snap target later.

Let me know if that self-snapping issue was not what you were seeing, if not then if you could possibly post a sample file that would help.

Also, one other note, that apparent intersection stuff will only apply when you are in one of the ortho viewports, not while you are working in the 3D viewport.

2. Another similar question which I think may have been asked, but i cannot find the post anymore: is there a way to add/create/show/manipulate edit points that reside on the curve which can be used to drive changes to the curve and snap to points where the curve must pass through?

No, there's nothing set up for this currently. In the future I want to try to set up something for this by a construction history mechanism, that would allow you to edit the points that you originally picked for a "Curve Through Points".

But if you mean something like the "Edit point" mechanism in Rhino, there are actually a lot of problems with that mechanism so I'm not really planning on doing that exact kind of a thing and also getting those same problems as well...

Check out this other recent post for some illustration and explanation on this:

3. Is there a concept of isoparms built into MoI? If so, is possible to use that as construction aid?

No, there's nothing set up in MoI currently for isoparms.

In Rhino for example the isoparm display has a tendency to obscure interesting details in the surface display, things like little ripples and bumps are often right at an isoparm and having a whole bunch of isoparms additionally displayed tends to get in the way from being able to see more of the actual surface itself.

So it was a focus in MoI to make a cleaner display and not one so choked up with isocurves - those are actually a remnant from the past in Rhino that is inherited from its original wireframe display mode.

I am planning on making a command for extracting an isoparm from a surface though so you would have it as a regular curve to use for whatever you want.

Is there something specific that you would want to get from isoparms ?

- Michael