Rebuilding surfaces, terrible result - control points everywhere! Need help to understand!

Hi everybody,

I bought the Audi R8 tutorial from Ak3d in order to learn 3d modeling with rRhino.


But since their support-section is closed I’m turning to you for help. Also I’m using Rhino for Mac but I chose this category since it’s bigger than the Mac-one and also because my post is purely about modeling and not the software itself.

Basically I’m trying to use the Create surface from 2,3,4 edges command to create different sections of the hood of the car. According to the tutorial I should use the rebuild-command afterwords and rebuild each surface to 6 points / 5 degrees. But when I do this my surfaces becomes totally messed up.
When I switch on the control-points I can see that the points are spread out in a crazy way (?) Can somebody tell my why rhino act this way? I realize that the control-points need to be reallocated equally over the new surface and at the same level of height in order to avoid this wavy shape, but what command does that? I cannot drag each point individually of course.

Step 1. Created surface using “Surface from 2,3,4 edges”-command. Turned on control-points to see how messy the result is

Step 2. Started the rebuild command. Changes the points to 6 and the degrees to 5. Should I uncheck the “retrim”-box? How does that affect the result of the rebuild?

Step 3. End-result of rebuild command: Wavy-looking with a terrible fold in the front and control-points pointing in every possible direction! What’s wrong?

Hello- keep in mind that EdgeSrf uses the structure of the input curves in the surface, so it might make more sense to rebuild the input curves first - this should avoid the skewed structure that you see in the initial edgeSrf. But, post all the inputs and someone will take a look.

-Pascal

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Thank you, Pascal.

Great advices right there. I splited the curves into smaller segments and rebuilded them. The biggest difficulties is the profile-line of the hood. I went back a couple of pages in the tutorial and read that tutorial told me that it should be created as a degree 5 curve consisting of 6 points, which I had done.
So I’m kinda surprised how the author of the tutorial can get a complete different result when our curves are close to identical to each other? Also I noticed that some of the curves have their control-points both “above” and “below” the curve which gotta be the reason that some of the surfaces get a “wavy” appearance. How do you avoid this? I mean you can’t drag all the points thats below the curve to being above the curve without changing the curve itself.

I attached a copy of my file before rebuilding the curves
Audi R8 5 views_help.3dm (201.6 KB)
maybe you or somebody else could it a go and try to analyze why my modeling failed. I strongly feel that I need to understand how rhino operates with these commands on a deeper level, otherwise I will be stuck as soon as I start model another object with complex surfaces.

I found also found an old topic on the support forum (before it closed) when the author tries to help another person with similar problem. His suggested solution were that the EdgeSrf command should be used by selecting the surface edges instead of the curves it selves if possible.
http://www.ak3d.de/forum/ak3d®-forums-group6/ak3d®-3d-car-modeling-with-rhinoceros-forum8/user-tipps-on-the-tutorial-thread8.1/

But when I do select the surface edges…

…The command fails like this!

What’s the reason for this? Why does the command fail when selecting the surface edges but not only the curves?

I think I’d put it together something like the attached - I am not sure what is supposed to happen along the fender there above the wheel (red and blue surfaces) - it does not look quite right but you’ll get the idea.
All surfaces are EdgeSrf, with reasonably good input curves.

To answer your question, I think - EdgeSrf uses the entire curve - it is somewhat ‘primitive’ in that it just uses the curves pretty directly as inputs - it does not care if one of them is too long, for example. So curve set up is key.

Audi R8 5 views_help_PG.3dm (822.0 KB)

-Pascal

1 Like

Thank you, Pascal! That’s really helpful.
Of course I’ve tried to put the control-points for each curve at the same positions as in the tutorial but of course you can’t get it identical when looking at a pdf with small thumbnails. This really helped me understand the importance of the curves input! Thanks again, I will try to “fix” my model this way in hope that it will work with the continues instructions of the tutorial.