Control Points and tolerances

Hello. I’m making an insole and sometimes I’m using control points to manipulate the surface. I usually write down which control points and how much I move them in case I have to change something and I usually start from the begginning since I’m not sure how control points work behind the scenes. My question is let’s say I move a control point by 5 units to the right and I then I move the control point 5 units to the left will the surface be the same as the one I started with?

I just have to make a minor control point move and I’ll probably be done with designing the surface and if I can move a control point back from my latest design it would save me some time. I’m attaching a picture with the control points.

Thank you.

Yes, within the floating point math accuracy which is around 1e-15 or 0.00000000000001.

Well, actually I don’t think it’s the floating point math that governs so much as the user’s ability to get the point back to the original spot. I doubt anyone wants to record original point locations to 15 digits of accuracy for subsequent return by typing in coordinates. Might be easier to just type in GUID’s. :grinning:

I’m not sure Rhino has any easy to use tools to drag a control point away from it’s original location and then drag it back to exactly the same spot. Maybe “undo” if he just wants to try a new location and then put it back right away. Another thing I can imagine, although I haven’t tried it, might be to snap an actual “curve” point to the original control point location where it could remain available for return snapping further along in the modeling process. Finding it later on might be a tough visual task, but if it’s given a unique name it should be easier.

Hello - modifying a copy of the surface is probably the safe way out, or ExtractPt and lock these to keep a record at any stage.


Of course! Listen to Pascal. He knows!