Hi

I am working on a small skiff that will be built from aluminum. 

The bottom surface was created with DevSrf in V4.

The file was brought into V5 and Unroll Developable Surface was used but the unrolled surface has a wrinkle. The wrinkle is outlined by the red torus in the attached drawing.

V4 unrolls the surface without a wrinkle.

Further this if either the V4 or V5 surfaces are offset (6.34 mm) and the offset surfaced unrolled things get worse.

So what am I messing up :)

John

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Hi John- I see that, thanks, I'll pass it along to the developer. Hmm- wait... I do see that the the 3d surface has an overlap of the control points at the corresponding location. If I adjust that, the surface unrolls correctly.

-Pascal
pascal@mcneel.com

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Hi Pascal

Your the best. How did you find it?

Whys did DevSrf create a wrinkle....anything wrong with the curves?

Thanks.

John

Hi John - it looks to me like DevSrf messed this up- I'll send that to the developer.

I found the problem by turning on the curvature graph (CurvatureGraph) on the 3d surface- the graph spikes, goes crazy really,  at that location. 

thanks

-Pascal

Pascasl@mcneel.com

Hi

I was not activating (if that is right term) the U & V surface hairs in CurvatureGraph.

Once activated the wrinkle spikes are crazy....and easy to fix.

As a side note I tried to loft a surface from the 3D lines and was never successful.

Once again thank you.

John

Hi John,

I'm interested in your interest in DevSrf.  As you've noted, its not a real consistent part of Rhino.  It never really made it into the main stream.  It was an experiment that never quite got to the point of attracting enough interest to get finished.

I know there are a few people who use it some and still I don't think it works well enough to be generally useful. 

So since you are one who uses it, I'm interested in finding out what your experience is.

I see above that you commented on the Extend feature, which I removed after deciding that it wasn't controlable enought and that it was easier to just exend the curves.  I guess you don't think so.

I'd like to make something that can make developable surfaces and works well enough that I don't have to keep it hidden from general use.

Are you interested in talking about that?

Thanks,

Lowell Walmsley

Hi Lowell

We start with a blank screen and build a finished product with everything in house. If anything doesn't work we know.

With everything there are areas that need to be compensated. We've built boats created with other software and the areas that need compensation seem to be the same. No knowing were to compensate could be behind DevSrf it not working well enough.

Far as we are concerned DevSrf is perfect......as long as a procedure is followed on the screen and in the shop the CNC parts fit every time.

To go back in history V3 we tried Loft. We found more success by dividing the 3D curves by an equal number of points, join corresponding sets of points with a curve (ruling lines) then adjusting the 3D curves (several times) if the the ruling lines didn't look right. Finally a surface was lofted from the ruling lines. DevSrf saves allot of time.

It would be great to talk.

John

I also have been using DevSrf and prefer it to Loft for developable surfaces in boat design. It does require more care in the curves than Loft, but I find the benefits are it doesn't generate polysurfaces where they are not really needed which Loft frequently does, and DevSfr provides some control of the amount of twist which is allowed. I don't have any problems with extending curves as needed and actually prefer doing that because it gives me control of the "corners" of the sufaces.

 

 

OK, I guess I need to understand what you guys do using DevSrf and what frustrations you have and not make up too much of this myself.

-Do you start with curves that you know are good enough to make surfaces from once you find the ruling directions?

-Would it help if you had a tool to adjust rail curves a little to make the surface more developable?

-Do you ever use DevSrf to work on more than one surface at a time? Keel to chine + chine to sheer for example?

-How do you know what to use for allowable twist?

-Do you use the Least twist / Shortest / Planar sections options?

- Are there things that you wish you could control or control differently in DevSrf?

Lowell

 

 

 

I try to start with curves which meet the requirements for a developable surface. If there is a problem with the curves then I go back and modify one or both curves consistent with the design intent.
Sometimes I manipulate one or both curves directly. Other times one or both curves are derived from other geometry and then I have to decide what I want to change. A tool within DevSrf to modifiy a rail curve wouldn't interest me.

 

I don't recall using DevSrf to work on more than one surface at a time.

 

More information about what allowable twist means would be useful; perhaps relating it Guassian curvature or similar. Currently I just guess at what to use.

 

I usually use Least Twist. My assumption is result is closest to a mathematically ideal developable surface.

 

David

Hi Lowell

David's comments are good

I'd add.....

Adjust would be useful but used with caution. Some curves cannot be  rebuilt with a set degree or equally spaced points. The keel curve on a planing hull for example. It is straight, degree 1 to the stem degree 3-4 with all but 1 or 2 points grouped onto the stem.

For rebuilding point count, degree, preview, create on new layer are useful.

I'll use DevSrf to work on sets of curves, Keel & Chine(s) - Chine(s) & Sheer to determine if curves work. If one needs to change often the others do. The surface are created individually as the extension varies for each.

Twist is difficult to define as it limited by the ability the fabricator. We've used twist tolerances between 2 and 6 for the same material some being wrapped by hand and others requiring clamps and come-alongs.

I'll use all 3 least, shortest, parallel planes to find the best set of ruling lines.

Along with swap rails how about Analyze/flip direction

 

John

 

 

Hi guys,

I just got Rhino 5 installed and thought I'd join the community, finally after using Rhino for years.

I've used the loft command to make successful hull panels, I've found the devsrf a bit confusing and it's hard to give up a method you know produces perfect results every time.

My method is to draw the keel and chine lines as I think they should look and then run the Loft command with history turned on. I then nudge the control points until an accectable panel appears. The panel is often a polysurface but that works for me.

I get a different result depending on where I pick the two lines for Loft, at the start, middle or end of the lines. Playing with the rebuild setting and tolerance also helps in getting good results.

Now while this works it would be great to have a bulletproof tool for making developable surfaces without having to "massage" the curves and settings so much.

Hi Lowell

Turns out the customer wants higher sides on the skiff so the side surfaces have to be redone. 

In V5 I tried to extending the chine and shear curves by 24, 36 & 48" none of which would allow a full length surface to be create.

If mess with the curves I'll need to create a new chine and frames.

I switched to R4 with an extension or .05 (12"+/-) DevSur created full length surface for the sides.

John

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