Creating accurate curves

I know I have been going about this the wrong way, but when I try the correct way my results are often bad and sometimes worse. Please bear with me as I try to explain my process.

I want to create accurate curves, including sharp corners. What I typically do, because I am so familiar with it, I will create them in Illustrator, because here I can create accurate curves quickly, with relatively few anchors/point. Like this:

When I import this curve into Rhino it no longer has very few points, it now has many more

At first this does not pose a problem. I can extrude fine, and do a number of other things, like creating embossed text. The problems start when I try to fillet the edges. It doesn’t work.

When I try to do this the correct way, by using PictureFrame I have not been able to create a curve that is as accurate as the one(s) I am able to make in Illustrator.

Not only that, the only way I seem to have been able to get anywhere close to as accurate a curve as possible, is that the result has nearly as many points as the imported Illustrator curve. And the resulting curve is not nearly as accurate as the one I had created in Illustrator.

I also can’t seem to get sharp corners where I want them. I have tried “Insert kink” and “Handlebar editor”, but I am not doing it right.

How should I do this correctly?

Hi Zews - if you are tracing in Rhino using InterpCrv, you will find it very hard to get clean and accurate curves - generally, use the Curve command (degree 3 to 5) and place your points approximately - then turn on the points and edit them to clean up the curve - use CurvatureGraph as an aid as well. Stop and restart the curves at the hard corners. Where the curve is meant to be straight, use Line, if it is clearly an arc, use an arc- e.g. make a hard corner and then add the arc using the Fillet command, or the Arc > tangent command, etc. Use Connect to trim curves to each other, as at a corner.

Tracinng_PG.3dm (444.6 KB)

HTH, as the helvetosaur says…


Hi pascal,

I did not use InterpCrv, I used Curve > Free-Form > Control Points, and made one long curve. Not with different sections as you did. I was not sure what I should use to edit the curve. Should I use EditPtOn (which places the points on the curve) or should I use PointsOn (which places the edit points besides the curve). What would be the best one to use?

Why would I use Connect instead of Join to join the individual curves into one closed curve?

I do not understand what CurvatureGraph does and how it helps in editing the curve. I see things change when I increase or decrease Display Scale and Density, but when I hit Done nothing seems to have changed.

What does HTH mean?

Hi Zews - first of all, I think, from the images, your curves are probably just fine… my comments were about how I would do this.

  • I would as a rule, use control points to edit a curve though edit points and HBar may be of use also.
  • Connect will trim curves to each other - if the ends are within tolerance, Join is of course the tool.
  • CurvatureGraph shows the amount of curvature in a curve - you can use this to analyze a curve for ‘nice’ curvature progression. Usually a smooth and progressive graph is desirable. It can tell you if the curve reverses in unexpected places that you do not pick up by eye. It does not change anything about the curve, it just displays some information that can be useful in editing the curve.

In this image the curves are very similar in shape but the graph shows me that the upper one is very sligjhtly reversed - ‘dented’ inward slightly from the overall shape (the graph changes falls on the ‘inside’ of the curve at the marked location, while the lower one stays convex and ‘fat’

HTH = Hope That Helps.