What method to lay these canvas petals onto the dome surface?

Hi,
V5


These flaps (petals !) are drawn as if on the canvas sheet laid out on a table before being cut (planar) and they are the correct spacing to place 8 around the dome base giving the V gap at their base.

I need to see how these lay onto the surface of the dome, they are the correct length so that the hole for the centre pin (not drawn yet) will all line up, there are 8 of them. (having done calcs on path length on elipse surface etc ! to establish length from base to pin hole)

Can it be that if I edit the curve of the planar flap the shape on the dome updates live ? That would be great, tweak the profile and see the effect update on the dome. How is that done ?

There shouldn’t be any gaps between them, overlapping all the way to the centre, except for at the webbing ring where that V gap exists and must hold its shape there as projected to the dome. (slight gap between them and the ring at the moment, (need to narrow the ring down)

So how does one lay these onto the dome surface as if they were canvas petals ?

How might I model these when done as if slightly rippled canvas material ?

rhino v5 file attached.
PETALS FOR DOME forum.3dm (1.2 MB)
Steve

Hello- this is what I am guessing you might want - of course, canvas will not deform this way but it may be close.

PETALS FOR DOME_maybe.3dm (1.4 MB)

(V5 this time)

-Pascal

Hi Steve,

The distance from the middle of the base of the petal to the centre of the hole is 11.74" but the length of the curve from the edge of the dome to its pole is 11.841"


So if the intent is for the petal to lie on the surface starting from the very edge, then they won’t quite line up.

As for laying them on the surface, I think the best you will do is as follows:

  1. Move one petal, its hole and the construction line to be centred on the quad on the edge of the dome. Group the petal and its hole. Shorten the construction line to the length of the petal. Get the length of the construction line. Delete the other petal.

  2. Create a curve from the isocurve running from the quad to the pole, the do the same for the isocurve on the opposite side. Join them. Divide the curve by length of segments using the length of the construction line, split the curve and delete the unneeded part.

  3. Select the petal and use flow along curve with the construction line as the base curve and the extended isocurve as the target curve to bend the petal around the dome.

  4. Delete the flat petal and construction line. Select the bent petal and use Pullback to pull it onto the surface of the dome.

  5. Delete the off-surface petal. Delete the extended isocurve. Group the remaining petal with the hole. Go to the Left viewport. Select the final petal and use polar array to complete the set of eight.

  6. inspect the result. The pullback will have distorted the shape slightly. If you are not happy with it, make a new petal adjusted to compensate and repeat the process.

HTH
Jeremy

Edit: Its quicker when @pascal does it!

Hi,
Pascal what method did you use ?
Jeremy, thanks for the step by step, thats EXCELLENT for learning, understood the entire process, thanks.
Pullback was a new command to me.

Is there a way of seeing it alter when altering the original planar shape ? would record history do that ?

Attached the file, I checked the dims, the distance on dome surface from edge of band (where petals start from) to centre is 11.741inch and the petals were 11.74

attached.
PETALS FOR DOME forum check surface distance.3dm (1.1 MB)
Steve

Yes, I see. You are starting them a little way up the dome, not right on the edge.

Pull & Pullback are different commands ?

The way it is documented does not allow me to distinguish both intents…

Then, Pullback is not available via the Cmd Line here (Only Pull can be parsed), is this a Windows thing ?
Rhino for Mac Version 7 (7.6.21103.13002, 2021-04-13)

!

!

Screenshot 2021-04-23 at 07.27.37!

Regards
Rodolfo Santos

Hi @RodolfoSantos,

Pullback was the name used in Rhino 5. It was subsequently simplified to Pull.

Steve is working in Rhino 5, so advice posted for him may not be quite right for Rhino 7 users.

HTH
Jeremy

Hi,
V5


Now to do this for a 3D petal/flap.
Just wondering on using pull on overlapping canvas where the dome is the outer canvas limit, se we have two surfaces to pull to, the last petal and the exposed dome.

It has an outer edging of 0.1inch overall thickness canvas material (contrasting colour, a protective edging sewn on), the petal canvas is 0.03inch thick material. The eyelet 0.1inch thick metal.
Ideally the eyelet wont get distorted, so I could position that afterwards.

As the dome represents the outer limit of the canvas flaps, and as I need each one in turn overlapping the previous one, how best could I do this. ?
Obviously the next petal will sit on top of the previous one but hug the dome beyond it.
Can I pull upwards and downwards after the petal has been flow along curve, pulling it up from dome to the outer surface of the previous petal and pulling down to dome of the part not overlapping the previous petal ?
Do I need to shrink the dome surface (offsetSrf) so that it is for the inner face of the 3D petals or can I select the outer face of the petals for the pull as the dome is the limiter for the outer face of the canvas ? (called Pull I see in V5)

I need I suppose to make a thin parallel surface for the canvas and recreate the edge also as an object. else there wont be any visual overlapping. i.e they need to be a recreation of the canvas thickness.
3D petals attached.
Flaps V4.3dm (499.0 KB)
Steve

Just to clarify: does the first petal, say, lie under the petals to each side, or is it under one neighbour but over the other?

Hi,
V5, note 3d file superceded initial attached file.
under one neighbour and over the other, each gets laid down over the last one in an anti-clockwise fashion. ) I had originally said clockwise) staring at it end on.

I just wondered, to get a fabric rippled look as would be, could the dome be ‘fabric rippled’ in some way, away from the large circular end where a webbing strap (as per start file, now made a bit tighter to hug canvas) keeps things down flat. then the pull would make the flaps appear like true canvas. Do we have a rippler command, useful for fabrics etc !

Steve

First off, you can’t use Pullback to pull a solid, only a surface, so there is no need to create a flat solid petal. You will need to pull one surface of your petal and then offset it to create the solid petal.

I think I would get the overlap effect by making a copy of the dome and the petal surface. Pull the copy petal onto the copy dome, then offset the petal to give it thickness. Cap the copied dome to make it solid and union it with the thickened petal. Rotate the union 45 degrees anti-clockwise.
Then flow and pull the original petal onto the union surface. If this is unsatisfactory, the edge where the two parts were unioned will require work - blending or more to smooth it out. Once you can get the petal to lie acceptably you can offset to get the solid.
Remove the union piece and form a polar array of the petals.

Hi,
V5

I have exploded this solid, deleted all but the outer surface of the canvas beige, run command PULL and it wont allow me to select a surface.

so I am stuck.

I had just completed a solid flow along curve to get the attached, your post just beat my post, the beige canvas sat before flow with its outer face against the base line. I have extended the petal to ensure the eyelet doesnt touch the edge beading.
I wondered if the base curve , as it was marrying to the target curve, had to be same length, so trimmed it at eyelet centre.
I then found out Pull doesnt do solids.

We have no command to pull a solid to a surface have we ? I am surprised there isn’t, I suppose thickness would limit it.

I will try and follow those steps but a lot more involved than the simple curves pull :frowning:

I could start with exploding this and using the outer surface, try to do as you say, then offset surface inwards, solid =yes.
The outer beading sits equidistant on the canvas thickness, so I would have to offset surfave b both. and initially flow to surface its centre surface, or should I extend the canvas to the brown beading outer edge (our original shape) and offset the resulting edge then try and make a solid from it. getting scary here.

Oh if only my dream was true, it was to ripple the dome, suck the solid petals onto it., each one taking up the rippled surface and the previous petal. That would have been quick, and effective.

Flaps V5 3D petals flowAlongCurve.3dm (2.8 MB)
Steve

Hi,
V5


I have after a few hours used a grid technique to get an accurate flap/petal, but now I cant see how to offset the edge .35inch to get the border. I tried offset but crazy results.
Flaps V5 3D petals flowAlongCurve.3dm (2.6 MB)

Steve

Hi,
V5.


I am now at this stage, but stuck on how to lay one over the other in a clockwise fashion and have the thickness underneath show., having gone a slightly different route and achieved accurate petal.
flapv7.3dm (1.0 MB)
Steve

@Steve1, sorry this is bad advice. You can’t array the eight petals, you have to create each one individually in order to stack the eyelets. That also means that successive petals must get slightly longer to accommodate the extra distance.

Hi Jeremy,
yes they would do so, I think for this I will let the client fiddle each one when on the job. There is also the fact that they all get placed over a brass spiggot then a pin placed through, so allowing for that as well, these will be max length and can be shortened but I bet in reality they were all same length.

Just how do I get to make these look like they overlap though, I could just trim each using the last, but its all very false, apart from the metallic sheen !
Is there a matt effect in shaded view I wonder, . I havent got time to study rendered view right now, this project , this is only a very small part of it, the cherry on the cake, has set me back weeks beyond deadline.

…and the rippled fabric, just how does one do such in Rhino, ? big ripples need 3D not a bitmap. Rhino is organic modelling as opposed to solidworks and catia, so a random rippling, even to creasing, would be a command, or maybe Mcneel rely on others to create a plugin, sticking to jewellery, houses , boats, engineering-ish, etc. Curtains in houses ?

I have heard of Drape.
I need to get the petal to suggest its sits on top of the previous one.

VacuumForm command would be good !
SuckIt command :slight_smile:

Steve

I can’t visualise how the ripples run - do you have a photo?

Hi,
Attached the best 3 I have.
ripples_3

ripples_1
They are laid down ANTI-CLOCKWISE, each in turn.
Steve

Thanks, glad to see those: I had visualised something much tauter, stretched over the dome.

Can you put off this aspect of the model until you have your new pc and can run Rhino 7? SubD would be much more suitable…

Hi,
That will at the current workload be months away, I am 3 weeks behind getting this handed over, then to focus on a few other jobs overdue by months due to this, then win10.
Forever getting to within touching distance of finishing line then shelving something, and never get it finished, Its supposed to be being made starting 3 or so weeks ago.
I will just have to say these smooth shiny things are in fact canvas and would be rippled, just looks crap to do final screen shots. Perhaps use photoshop to spray some shadows and highlights in.
Just so surprised that Rhino has no fabric effect at all, googled it, its never been considered, as if its not an engineering thing although Rhino isnt just engineering but organic shapes.
Found a poster wanting to create the canvas gon cover for a Rhino modelled WW2 tank and he ended up having to draw cross sections and adjusting each one, then laying a surface down over it.
I know in mesh progs one can create clothed figures in minutes.

I have boolean split each petal to at least get the look, albeit totally flat and all solids as one.
as such :-

Intrigued on what Sub D can do regards ripples and creases in fabric I google Sub D fabric Rhino7 but find nothing, cuos and rabbits but no fabric.

Steve