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# How to make curved surfaces tangent one another? A hard task

Hello, I try to make the front of car body of curved surfaces which are tangent to one another (It must be so as that body must be aerodynamic). I have nearly done it- when I zoom in that body there appear discontinuity on edge separating these two curved surfaces.

I have been struggling with this for a week - I have to close the space determined by curved surfaces: red and blue with the green curved surfaces(bright green and dark green ones). That green surfaces must tangent be to these red and blue surfaces and must be smooth themselves.

What you can see in the first picture is what I ve managed to do. It looks as if it was done ok, but when you zoom in and reorient it (2nd picture)you can see that the green surface has its "belly" -it is not tangent continouos to the red surface.

you can also see some discontinuity in the 3rd picture(when bright green goes to dark green )

These green surfaces where created using bluesurf and their edges where used as guide curves. When I added tangent continuity and normal to section conditions where they should be it gave no difference.

How can I deal with this no-tangency problem?

thank you,

4 REPLIES
Solution
Solution
Accepted by topic author rhcp89
‎08-26-2015 04:32 AM

## Re: How to make curved surfaces tangent one another? A hard task

Hi there,

All of this should be easy enough, depending on the conditions the surfaces have be applied under. Such as, are they derived from only the curves?....if yes, then there is likely to be the problem. Reconstruct one using the surrounding surface edges, and the position & continuity conditions can be controlled.

If this doesn't fix it for you, maybe upload the model, so we can offer alternate solutions.

Sean Cresswell
Design Manager Streetscape Limited
Solid Edge ST9 [MP3] Classic [x2 seats]
Windows 10

## Re: How to make curved surfaces tangent one another? A hard task

Big thank you!

That was as you said- the curves from sketches were used as an input to make guide curves for bluesurf. So I used these curves which define the surrounding curved surfaces and then... the bluesurf failed to generate. I dont know why. Why did that bluesurf fail?

But then I used bounded command instead, again used the edges of surrounding faces, then added tangency conditions and it looks really great when it zoomed in.

## Re: How to make curved surfaces tangent one another? A hard task

If you are trying to match surfaces, for the second surface, use the edge of the first surface rather than a curve. Plus, you'll have to make sure that if the last surface is the green surface, and you want it to be tangent to both the red and the blue, then you have to make sure the red is tangent to the blue. This sounds silly, but I've seen a lot of cases where people forget that. If one of the surfaces is extruded, things become a lot easier.

There's a book that might be helpful to you. It's out of print, but you can still get an electronic version on Amazon. It was written for different software, but most of the same ideas apply. It's called Surfacing and Complex Shape Modeling Bible.

Matt

## Re: How to make curved surfaces tangent one another? A hard task

Hey Matt, Whens the updated Solid Edge edition of that book coming out? That would be something I would buy!