Thanks Michael. Much appreciated. I tried with the trim approach and then tried blending like in the orig tute and could never get the blend to work all around. Just curious, how does Rhino do this?

Hi Chipp - the Blend command in Rhino has options for setting different continuity levels on either side of the blend, and one of the options is just "position" continuity rather than making it smooth at all. That tutorial used that particular feature of disabling smoothness in the blend just on one side of it. Also it's not meant to go all around in one shot, you'd do the blend in 2 steps just one side at a time.

- Michael

Hello chippwalters,

Have you tried creating the crease by Sweep? Try creating the crease profile and using a scaling rail or both ends pointy and then doing some clean up work, it's not exact but may be close enough short of using Rhino.

Thanks for the idea, but I don't think it will work as it can't be perfectly blended into the main compound surface.

Hi Michael,

I was able to duplicate your tutorial just fine. See below for the 'oil slick' lighting which shows a very tiny cut in surface continuity. I created a path from the patch boundaries, and swept a small circle around it, then trimmed the resulting pipe to a shape which could then be used to trim a hole in the surface. Once done, I tried using BLEND, and while it worked, it created 'bow-tie' loops at the corners which left tiny holes in the corners. Other than the holes, the surface continuity worked much better.

Can you take a look at this file and see if you can trim out a blend area which stitches correctly? And if you're successful, would you please share your technique? Once I get this, I'll document in a video. Thanks.

File:
http://dl.dropboxusercontent.com/u/3788438/3D/TestRidge.3dm

Current file image. Note 1 and 2 showing surface continuity issue.

Michael,

Nevermind. I did a rendering in Keyshot and the boundary is barely noticeable.

Nice result Chipp. Be sure to show us the final model and render (or at least a zoomed-in portion).

Ed Ferguson

Hi Chipp, if you did want to increase continuity one way would be to untrim the main surface and then retrim it with a curved boundary, and also trim a similar curved boundary on to the inner piece, then you can put in one blend between them (using "Add sync points" to match up points to avoid twisting), looking like this (see attached 3DM file):



- Michael

Also for an increased continuity version it may not be a bad idea to trim off a little bit of the outside of the ridge part, sometimes when you want to blend something smoothly to another surface it can be better if the 2 sides don't try to come to the exact same shape because if one side just very slightly swoops upwards that upwards trajectory will get exaggerated in the blend. So it can sometimes be better to stop a shape while it is for sure going in one consistent direction before putting a blend on it. That's what trimming away some of the outside of the ridge part can help with.

Then to get a good blend you need to use "Add sync points" especially right before and after each corner, so the blend does not get twisted up as it tries to go around the corner. Also in this one I used Planar sections as well:





- Michael

Michael, thanks so much!

Great advice. Here's the tutorial I promised. Let me know if there's anything wrong or I could've done better. Thanks again!

Hi Chipp, looks good, thanks for posting the tutorial.

Just a couple of comments - when you select the edges for the blend you can actually select them in whatever order you want, blend will automatically sort them as needed. Not that it's bad to select them in order though, it just isn't required.

And also when you go to do "Add sync points", you can keep adding in as many pairs of point as you need just with one click of the "Add sync points" button, you don't need to push "Done" and click the button again after every individual pair.

- Michael

Nicely done Chipp :)

Martin
(TpwUK)

Thanks Michael and everyone for your help in figuring this out.

FWIW, I believe this is more than just a 'ridge' exercise, but a way in which anyone can add any type of continuous blended element in an already created surface.

Here's another cool use for this same technique:

Hi Chipp, that's looking good! Yes, using Flow for the construction tends to be more general purpose.

- Michael

Hi Michael,

Yes, Flow is great, but it doens't create perfect continuous geometry unless you use your double trim / blend technique. Thanks again for sharing that gem!

tricky!

Hey chippwalters,

"Flow doesnt produce a perfect continuous surface"

It will work much better if you make the base surface more of a replica of the target surface...

I had some ideas on this but will be away for another week or so... mostly i wanted to try to use a fillet on the compound surface to get the curve, as opposed to a straight offset...

"It will work much better if you make the base surface more of a replica of the target surface..."

Not exactly sure what is meant here. As far as I can tell, the base surface is a rectangle; the same as the target surface. Only one is bent and the other is not.
Perhaps what you're saying to to try and create the the base surface from the target surface, then edit it? If so, I suspect there still may be a slight continuity issue.

"""""Not exactly sure what is meant here. """""

It has to do with flow analysing the 2 surface structures... When they are disparate, then the result can be distorted a bit...

SO like is the rectangle edges and size the same as the target edges and size? (for 2d) For the 3d surface, the actual structure of the underlying surface matters too. So the target surface, turn on the points for it, then look at the points for the base surface....

There are some demos on the forum that demonstrate the topic.... I am away in cali so can't really get into it too much...