# Variable offset / thickness

Hello Martin and thank you for the suggestion.

The thing is - since the whole algorithm is build considering two surfaces, base and offset - I don’t want to have polysurfaces, in addition my aim is to have a really smooth transition (the thicker area shouldn’t be so visible).
In the current version of my model I have a base SubD and an offsetted and adjusted SubD, but I found it hard to control the thickness of the second one, so I wanted to create it in GH.

Here’s a section of current SubDs, with a given thickness is a specific area, that gradually decrease.

To convert the brep to a single surface, you just need to project a grid of points onto the base brep.

sporph_brep_surface.gh (9.5 KB)

Test1d.3dm (414.4 KB)

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That trick of the BREP->Surf is awesome, and I’m pretty sure it will be very helpful in lot of situation.

The problem with the FlowAlongSrf method it that the base surface is really complex (it is base on the scan of a body part) and I didn’t find an effective way to “unwrap” it on a plane (usually I make Contours section on the 3D surf and then I calculate the lenght to create a flat loft surface).

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Yeah, using surface normals to move the offset points is correct - the way offset surface works.

I spent some time yesterday and this morning working on a smooth transition between offset areas. It’s difficult, especially handling multiple offset areas with different offset values. I finally got something that seems to work as intended, but more testing is required.

The big Eval component that generates the vector amplitude values is a fail in the sense it is hard wired and must be modified when the number of curves (offset areas) changes.

I tried a different approach today that somewhat simplifies the task. Offset Surface is used with the default distance value (‘offD’ slider = 15) and is then used as the input to SDivide. ‘offB’ and ‘offY’ (offset values for blue and yellow curves) are modified to be relative to the default (-5 and +5).

The disabled Cull (yellow group) shows points in the transition areas, affected by the ‘Range’ slider (blue group). The Graph Mapper shape determines transition offset values.

I don’t know anymore if it’s correct and at this point I don’t care! Too much time spent… The result is smoother (and slower) if you bump the ‘U Count’ slider up to 200. Requires Rhino file Test1c.3dm.

variable_offset_2023_Aug17a.gh (32.2 KB)

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Hello Joseph.

Thanks for your time. I have a lot to learn here, expecially concerning the Graph Mapper and its potentiality. I’ll try to achieve more smoothness though, since I’m struggling with that now.

Try Land Kit! It has topography manipulation tools that let you grade, sculpt, and smooth, etc. and then you can project different shaped areas to that topographic mesh and then even between two topographic meshes to get a variable thickness slab like you are showing. It would make your process way simpler and more flexible.

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Hello Chris, thank you for the suggestion. I’ll try it for sure!