Help with modeling_Using just single span surfaces

Can anyone tell me how to model this Light fixture using just single span surfaces. I tries multiple time to model but somehow i do not get the right curvture in both direction. I tried to train myself first by lofting cross sections / create surface from edges but those were the results and do not think i am going in the right direction… I hope if anyone can help…


Hi Khaled - please post a file with what you have so far.


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Sure… It is just full of alot of Trials

Light Fixture_trials.3dm (8.0 MB)

Hi Khaled - I think I would shoot for a surface patch layout along these lines - you’ll want to be more careful than I was about the consistency of that transition surface but something like this ought to work:



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Thanks alot Pascal. I will try to do it as you have done and will update you

@Khaled_Ashraf1 - the tricky corner transition will work a lot better if the revolved surface is non -rational - make a version of the revolve that is 'Deformable=Yes" and use that to MatchSrf your surfaces to, then trim them in to the actual rational (Deformable=No) revolved surface if you want, afterwards. MatchSrf does not always do as well with exact revolved surfaces.


@pascal the surface is actualy not a revolved one as it is at the bottom more circular and as it moves up it become more rectangular. How can i turn it to deformable if it is not a revolved surface but lofted Surfaces?

-Regarding to your first comment about apply patch surface-- When i creat this inclined part by surface from edges it always generat polysurface not a single surface that i can not apply matchsurf on it. So to move on i tend to explode/unjoin them to get single surface. but then it gets complex.

-And sometimes when i matchsurf, it just work on one end of the surface and on the other not, it shows(not trimmed surface). Is there a reason for that and how to get over that and match the other end too?

Sorry alot of Questions but i am trying/training to get clean model with min Surfaces.

Definetely check out if you haven’t already, by @sgreenawalt

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Light fixture_T1
Hii @pascal could you show me how did you start the surfaces patch? I stopped at that point

Thanks alot @Gijs. I am already following him. He is the one who motivated to use just single span surfaces

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Hi Khaled- please post the file in that state.


Light Fixture_T2.3dm (256.6 KB)
Hii @pascal , here it is. There is also another trial next to it.

having fun yesterday I tried several approaches to find a solution with as few surfaces as possible.

I don’t know if this is good enough for what you want.
anyway, here it is.
luminaire.F .3dm (3.9 MB)

video is here
it just shows the main body modeling

I looked at your 3dm file that you shared.
I saw that you used degree 3 multi span curves to create your surfaces of revolution.
It’s not a bad approach. But it won’t give you single spans!
unless you reconstruct your surfaces. or you redivide them on the isocurves

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Hallo Fares, Thanks alot man I appreciate your help. That is very nice from you.
I will try to do it again and update you…

Hi Khaled - given whart you have here - everything matching for tangency - I think I might go about this as in the attached file - if tnat seems like what you are shooting for, I’ll lay out some steps.
Light Fixture_T2_Maybe.3dm (354.9 KB)

I see Fares also has something for you - hopefully between the two of us you’ll get started.


In my opinion, @fares.boulamaali already showed the most appropriate way to create such kind of shapes. I would use the same technique, even though it’s a waste of time to do so, since a manually sculpted single multi-span surface with gazillion control points :rofl: could do the job 100 times faster and easier, while maintaining perfect surface quality. Anyway, here is a step-by-step video tutorial showing the creation of a single-span model, in case that someone needs to waste over 40 minutes. I managed to do some minor mistakes during the video, so ignore those few moments. :slight_smile:

Since Rhino is unable to properly loose offset single-span degree 5 surface and creates chaotic output surfaces, I used an old “hack” with using the hugely underappreciated “MoveUVN” tool to offset the control points instead. That results into almost flawless loose offset surfaces that need just a few touches to maintain their tangency along the border.

P.S.: The 4K/60 video is still being processed by YouTube, but should appear in a couple of hours.


Hi Bobi, I enjoyed your video. I could learn some things from you.
I was noticing something in your cursor movements as you worked. It was with the purge history. I saw you had to track all the way up to the command line to click All. That seems like a stretch from my point of view. It would be nice if it was on a right click for All. Just an observation. Thanks for sharing what you have done.—-Mark

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thanks for the video.
To make the initial surface Degree 5x5 with 6x6 CVs.
Why do you use RebuildUV, 6 CVs, ChangeDegree, RemoveKnot.
instead of directly ChangeDegree to 5x5 ?

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Hi Tom - RebuildUV only makes degree 3… I guess Bobi is working around that. With six poiints it has internal knots.

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