Water balloons and string

For lack of a better description, I am trying to draw a water balloon that has several strings tied around it creating a series of shapes where the balloon is bulging past the string.

I don’t want to spend the money on T-Splines.


Picture reference?

First thing that came to mind:

do you plan to take the model to animation or it would just be a still image?
will it be floating mid-air (like half thrown) or it will just lie on the ground (blobby-look) ?

it is better if you tell us exactly what you plan to do with this model.

I don’t know why you would need T-Splines, there’s a dozen ways you could do this in Rhino.
Here’s one using my favorite surface-creation tool; BlendSrf. It gives you lots of control over the shape while requiring little construction geometry.

balloons.3dm (4.8 MB)

I think if I knew how to draw either the Michelin Man or Marc’s balloons I could figure out how to draw what I need. The Michelin Man is probably closer. If you took just his torso, cut it in half vertically and flattened it out a bit, then wrapped more strings so you had a bunch of irregular shaped polygons that would be pretty close to what I’m after. Only thing I can think of would be alligator scales if there not so many of them and they were soft and bulbous instead of pointy.

I don’t need it for animation, but if the client approves it will be cut from wood using cnc router. It is just going to be one face of a six sided object.

I brought up T-Splines because other post in this forum and others suggested them to other people trying to draw similar shapes. I know there has to be away to do this using Rhino alone, I just lack the skill.

I think I see what Marc is talking about using BlendSurf, but I’ve only used that command once or twice and am not that familiar with it, but I’ll see what I can figure out.


I attached a 3dm file in my post too. Check it to see how it’s made, very step is on a seperate layer.

I saw that. But when I opened the file there is no list of commands in the top box. I tried clicking the different layers but nothing changes.

I never use layers. The ones in Rhino are confusing to me and so far my drawings have been simple enough I haven’t needed them, so I’m probably doing something wrong.

Hi John- the little lightbulb icons control the visibility of the layers. You can select a layer in the list and choose ‘One layer on’ to isolate just this layer.


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Thanks Pascal.

I don’t think BlendSurf is going to work for me. Looks like you can only blend two surfaces, where as I want my shapes to have 4,5, or 6 sides each.

When I was in art school there was a guy who would weld up a cube of metal rod. He would then randomly weld other roods on each face of the cube creating different size and shaped polygons with different numbers of sides.

He would then stuff and inner tube inside the cube cage and air up the tube until he had all of these different bulbous shapes sticking out. In some areas they would completely surround the rod so all you could see was a crease. In other places the inner tube would just protrude out a little to create these pot belly looking shapes.

That is what I’m trying to draw. I’m starting to think I should just move on to the next idea.

Hi John- can you post a picture of what you are trying to get at?


This is my best attempt. I want the shapes on the right, but I want the tops to be curved kind of like the ones on the left, but more natural. Think of a bikini top that is too tight. Best way I can explain without getting too racy.
bulbous 1.3dm (776.0 KB)

This may get you partway there- the roundy corners are a little more work though.

Three and four sided shapes are easy - make an EdgeSrf from the lines bounding the shape - make sure they are simple 2 point lines. ChangeDegree to 2 on each direction on the result, and lift the middle control point on each surface.

More than four sided and you need to get creative- Patch may help - makes a dense surface but might be the way out.

bulbous 1_PG.3dm (241.5 KB)



Here I used patch with points and flowalong srf
split the lines into pieces.
add points as you like on the Cplane - patch using the relevant lines and points.
elevate each points as you wish, using history.

You can then flow these “bubbles” along a surface, to create “body”.

Hope this helps


bulbous 1.1.3dm (1.2 MB)

i would model the blob without bulges as simple as possible (untrimmed surfaces, if possible), output a (quad) mesh and “inflate” the mesh with rhinomembrane (rhino-plugin, demo version)