Is there a way to get Rhino (V7) to remember the last ‘bias’ applied to a Blend curve? I need to replace loads of arc fillet curves before exporting to PDF for line artwork. Rhino makes a pretty ugly job of turning the fillet curves into Beziers. Tangency gets lost. Is there a fix for that? Has a bug report been filed?
This is screenshot when in-command, using BlendCrv. The black line is the original arc. The green line is Rhino’s attempt to Rebuild the arc into a degree 3 curve. Not great. The outer purple line is what Rhino offers as default if I call BlendCrv and the other purple line that’s very close to the black arc is me Shift-dragging the intermediate CP’s to manually approximate the arc. As you can see, I can get a lot closer to the Arc than Rhino can, for some reason.
If Rhino remembered the last ‘drag’ of the CP’s if I call BlendCrv again on another fillet arc, this would be a tedious but relatively quick task. As it is, each and every BlendCrv I draw will have different bias.
As an aside: Could this replacement of arcs with BlendCrv’s (properly fitted to the arcs) be scripted?
Hi @MattE
If I recall correctly (and I might not!), just use ChangeDegree to change the curves to degree 3, and you should be good to go. As long as you’re going up, the curve shape shouldn’t change.
Other than that, I imagine McNeel would love to see one of those PDF’s, because arcs should of course not be a problem! So for starters, run SysInfo in Rhino and post the result here. Also, what PDF printer are you using to print the PDF’s?
HTH, Jakob
Hi @Normand ,
Replicating the problem isn’t difficult: Draw a polyline to make a right-angle corner. Fillet the corner. Save that out as a PDF using Rhino’s in-built PDF (SaveAs…PDF). Open the result in Acrobat Reader or Import it into Rhino. If the conversion to PDF maintained tangency then I would have a problem. I’m not using anything that doesn’t come with stock Rhino V7. V5 export to the old .ai doesn’t have the problem, but Affinity Designer can’t open that, so it’s a dead-end in work flow terms.
Converting all the fillets to degree 3 is a chore I could well do without, especially as it makes any downstream editing awkward (using Offset, for example). So I’m temporarily saving out what I want to get into Affinity, messing about with the fillets, saving to PDF, then deleting the Rhino file. It’s not an elegant way of working.
I’ve just been messing around with FitCurve and its tolerance settings to see if that provides a solution, but it jumps to a 5 point degree three curve to get what I’d consider an acceptable result. I’ll try ChangeDegree…
As already suggested by @Normand , raising the degree from 2 to 3 should do the job, because the shape of the fillet curves remain the same.
You may also try the following settings while you export the curves to PDF, AudoCAD or any other program:. Rhino’s default settings result into destroying the original shape of the arcs by converting them into multi-segmented polylines… Simply click on “Edit schemes” and repeat those settings. They work flawlessly when I export my curves to any CAD program for laser cutting, printing or engraving.
@Normand - As you say, ChangeDegree works, where Rebuild or FitCrv does not. Thanks for the tip-off.
However, that is not the end of the problem. Tangency is still lost. See the attached file. Even if I convert the radiused corners using ChangeDegree, Rhino does ugly things when saving out as a PDF. This can also be seen just by opening the PDF in Acrobat Reader, so it’s an export problem with Rhino V7, not import. Is this a bug?
@Rhino_Bulgaria - I don’t want to export to .dwg or .dxf If I can avoid it, as they’re not great in Affinity, even in their V2.0 release.
@Tom_P - Yes, I might give .svg a go. But if PDF export had this corner problem sorted out, it would be great for getting artwork created in Rhino into Affinity Designer. Everything else seems to port over nicely.
Something I noticed when I re-imported the PDF in the attached file is that the font for some text in the orignal file came in as Bold where the orignal is Medium. When I try to correct that, the text resizes from 11mm to 1mm high and the placement goes wrong. I’ve deleted the text in the above file because it’s a proprietary font that won’t read correctly for anyone else. Everything was created on this PC, so the font is present both out- and in-bound. Likely another bug?
Yeah, just tested it - looks like a bug! I wonder if some of the more drafting-knowledgeable people know if this is a known bug/limitation or something new. I never do drafting in Rhino (we use SolidWorks for that), so I don’t know
Hopefully you’ll find a solution!
-Jakob
The current WIP seems to export a rounded rectangle correctly as a PDF - the corner arcs remain tangent in the PDF. They are still converted to degree 3, so they are no longer true arcs. I would not want to depend on PDF exports to manufacture anything with precision.
I’ve also read that V8 can copy/paste curves on the xy plane directly into Affinity (and possibly the same is true from Affinity Designer, which would complete the round trip), which would be a brilliant fix for this.
Problem is, the V8 UI mess has scared me off using V8. I’ve wasted so much time trying to make the workspace usable (for me) that I don’t want to go there again until things have been sorted out.
@Helvetosaur - I don’t think Illustrator or Affinity Designer support weighted control points, so they are unable to interpret true arcs or circles. Not as Rhino creates them, anyway. That, in a nutshell, is the root of the problem.
Some coder, somewhere - be it in Rhino, or Illustrator, or Affinity - has to convert the arcs/circles into 4 point Bezier curves. So this is about finding the least destructive, most accurate and simplest way of navigating the translation.
The files I’m working on in this instance are mainly for print, though they also define the cut paths for the labels. It’s all DTP stuff.
Well, in my example PDF above, the 4 point splines are only about 0.001 away from a true arc (R10mm). I don’t know how that will work with other examples though.
Hi Pascal. I’m giving up on that approach and giving things a try in V8. The Rebuild route looked like being very labour intensive anyway. I have a few hundred corner fillets to replace. If copy/paste works in V8, it means I don’t have to create any translation files, which would be great. BUT that depends on what the “copy” out of Rhino looks like when it lands in Affinity. The simple way to find out is to fire up the V8 again.
So my question perhaps should: Which is the best thread to go to to help me customise the Popup toolbar? (if that is now possible).
The answer probably begins with “Mitch”. But that’s a question best posed in another thread, I think…
Rebuild to degree 3 with 4 points results in exactly a (non-rational) degree 3 Bezier curve with 4 points. The deviation from an exact arc depends on the angle of the arc.
I’ve just saved out a few rectangles with radiused corners from V8 using Rhino’s pdf exporter, and it looks as though this problem is back. When I open the pdf in Affinity Designer, there is a clear ‘kink’ at the join of the straight and the curved corner. The ends are coincident, but not tangent.
