How can I measure along a complex curve? If, for example, I have a point on a curve and I want to move that point along the curve by a defined distance, how can I do so?
There isn't a "canned" function in Rhino for this. One workaround is as follows:
1) Call the command SubCrv, set copy to Yes.
2) Pick the curve on which the point lies, then the "from" point
3) Enter the length to move along the curve, Enter
4) Move or place a new point at the end of the resulting subcurve.
5) Delete the subcurve.
This is relatively easily scripted in Rhinoscript, I can see if I can concoct one later, if Chris hasn't already done it.
Here's a script that will do what you want. Drop it on an open Rhino window and follow the prompts. If you like it you can put it on a button or make an alias for it. I use the term 'sub-curve' in the command line but no sub-curve is created. I just needed a way of indicating the direction you might wish to move the point. Calling each portion of the curve divided by the point to be moved a 'sub-curve' was the way I decided to do it. I've also printed the length of the curve in the command line.
Moving a point along a curve will allow me to complete the operations I want, so thanks very much for that, but it was just one example of a type of operation which I find myself needing fairly regularly. For example, recently I needed to extend a surface along a curve. There's surely a way of doing this which I'm not seeing, being relatively new to Rhino, but just identifying the point to which the surface should extend was a challenge, now solved. Thanks again,