Shrinkwrap but not shrinkwrap?

[Richard_Duke]

Hi all, new here and newish to Blender…

Below is an image of a 3d scanned object I am trying to recreate and modify. It is essentially a bunch of marbles crammed into a rubber bicycle inner tube.

I am wanting to model it by positioning a bunch of spheres, and then stretching a cylinder around them, I want to be able to reposition and scale the spheres on the fly, until I get the desired look from the outer stretched surface. I then need to export the stretched surface as a quad mesh, for the purpose of solid modeling in other software for manufacturing a mold.

I have been playing around with the shrinkwrap modifier as it sounded like the logical solution, but after some testing, it doesn’t seem to give me that nice stretched transition between spheres no matter what options I try.

I was also recommended metaballs which actually does a pretty good job, but I also need to model variations of this with other non marble shaped objects, so really looking for a “shrinkwrap” style approach.

So I am wondering if anyone has any suitable approaches?

[pafurijaz]

I can suggest using the newer version of Blender 3.2.

Make a copy of the mesh, then enter sculpture mode and use the Remesh (Shift R to control the resolution and CRTL R to apply the command)

Once you have a suitable mesh, you can use the Shrink Warp command and use your original object as the target of the modifier.

Then apply the modifier and export the quad topology mesh to Nurbs CAD

But the best is to do manual retopology to this, you get the best result.

Greetings.

[Richard_Duke]

Thanks for the info, I will do some experimenting with this. The original 3d scanned data is actually no good to me, I need to create a 2-part mold and there are too many undercuts to use a straight split line, which is why I need to reposition the underlying spheres.

[pafurijaz]

If you have to make a straight line you will have to do it with the cad, but you can also do it with the booleans by subtracting a cube from one half and doing the same with the other part, so you will have to make two copies and apply a subtraction first to one part (upper ) and another to the lower one. But if you share the model I can try to make the model with this method.
Greetings.

[bestelix]

An idea would be to use a simulation with negative pressure but I know it can take some time to find the right settings.

[pafurijaz]

I’ve tested with my Workflow to make IGES from Subdivision surfaces with FreeShip.

Here the result from a similar object generated with metaballs.

Blender metaball shape remeshed (left selected)with sculpt mode and shrink wrapped on the right model.

And this is the IGES model imported into FreeCAD

Surfaces edges visible.

Greetings

[Nanomanpro]

Negative pressure seems to be a good idea.

Negative pressure.blend (3.7 MB)

[Richard_Duke]

Thanks, all. I’m blown away with the effort in your responses much appreciated.

I actually had some decent success with the shrinkwrap tool, but by adding a few more modifiers like decimate, + Smooth Corrective, then subdivide.

But thanks @bestelix and @pafurijaz I am still exploring both your options.

[Richard_Duke]

I knew this would happen, after putting the model together we then had to tweak the position of the underlying spheres, which resulted in recreate the surface using a bunch of modifiers all over again. I thought I would try the negative pressure cloth sim approach based on @Nanomanpro 's example. There was a lot of tweaking of various values to get the desired result, but I am super chuffed with the result so far. And as a bonus, we can now move the spheres around with easy until we get what we like!