Alt+S on XY only (Lock Z)

I have a model that I want to shrink (not scale) on just the XY axis only. I want the Z axis to be locked. After a lot of Googling I discovered that Blender has a Shrink/Fatten tool… so I downloaded Blender.

A lot more Googling and I figured out how to load in my model, go to the modelling tab, press Alt+S, type in -0.1 (to shrink by 10%), but now I’m stuck… and my Google foo is running out… so here I have found myself.

The problem is that the Z axis is also shrinking by 10%, but I want it to stay where it is. I only want the X axis and Y axis to shrink. Shift+Z only appears to work when scaling, not when using the Shrink/Fatten tool.

Is there another way, or a way to lock the Z axis when using the Shrink/Fatten tool?

The problem is that this tool you are trying to use uses the face normals to deform the mesh. It does not uses the axis.

To scale only on the x and y axis in less 10% you press S and shift z and write 0.9, or just .9

This is the way I know you can deform your mesh on the X and Y axis at the same time and not the Z.

Yes, that’s what I want to do. I want the mesh to “shrink” not scale. This will allow parts of the model to become thinner according to the surface normal. I was just hoping there might have been a way to constrain the z axis from contributing to this “shrinking” effect.

Sadly, it’s not possible, but you can use a lattice modifier for that.

First you add a lattice object to your scene that surrounds the object you want to deform. Then you apply to your object (the one you want to deform) the lattice modifier and link the modifier to the lattice you just added to your scene. Edit the resolution of your Lattice to have as many subdivisions as you need to work.

Enter edit mode in your lattice object and edit its vertices to deform the mesh it’s connected to.

When you are satisfied with the result you can apply the modifier.

The lattice surrounding the object:


Deforming as you desire:

shrink/flatten selected faces only

select x and y faces only, keep top and down faces deselected and use shrink/flatten or push/pull.

Could you upload or at least show the model you want to do this to? The only thing that comes to my mind is that you have multiples collumns which you want thinner but not smaller (in height).

I may have an idea on how to achieve this, but it would be very case dependent.

You can do it in geometry nodes, although it’s a bit inconvenient:

Add the vertices you want to shrinken/fatten to the vertex group “Group” (or all of the vertices if you want to apply it to the whole mesh)

and implement this setup in geometry nodes:

Here, I added “vertex_normal” and “disp” as new vector attributes, and vn_x, vn_y, and vn_z as new float attributes. The idea is to set the z-coordinate of the vertex normals to zero and displace the vertices along the resulting vectors. (alt-s moves vertices along their normals).

you can control the displacement with the value node at the bottom. If you copy the geometry nodes modifier to your mesh, it should also work. Here’s the blend file:

limited_shrink.blend (129.9 KB)

Video I used as a source: https://www.youtube.com/watch?v=DQVYieRfQBY

Thank you all for your help so far.

I don’t think I have permission to share the model or pictures of it at the moment. It is a standing humanoid figure that I need to shrink without shortening it.

Thanks for your detailed help. Although most of it goes over my head as I’ve never used Blender before until now. I did download the file you provided, however upon opening it, I can see the Icosphere in the scene collection and in the viewport, however the node grid below is blank, so not really sure.

maybe at least show something that looks like what you’re trying to do?

Yeah, I had switched to a different node editor before saving the file to delete some unnecessary stuff.

You can switch to geometry nodes by clicking here:

and selecting the geometry nodes editor:
image

(in the file it was probably set to the Shader Editor)

I think this discussion is fruitless because it’s the wrong question. In the following image i share my exquisite human base model with you to explain :wink: : On the left side is resizing. What we would all agree, you don’t want for you standing humanoid figure (overlapping geo). On the right is shrink, what would be a (reverse) solution for clothing (so fatten… same distance to all verts). And in the middle i snapped the vertices to there former z-value… (and this is good for ?!)

So the question for me would be: Would do you want to archieve with your approach? Maybe there is better/ or simpler way. (Maybe just shrink and slighty resize in Z???)