How to resize / shrink a non standard size hole

[Anonymous]

Hi guys, just discovered stl files and 3d printing. I have a non standard sized hole that I want to resize but not change the size of the rest of the object.

Someone at Reddit suggested I use Meshmixer. Any ideas and would you point me to a quick resource to get me going. Is there a touch-up tool where I can freehand fill in space as well?   Here is the reference pic: https://i.imgur.com/rrP8lY6.png

Thanks in advance.

[hfcandrew]

Select the inner ring of triangle you want smaller > Deform > Transform. Click and drag the coloured squares to scale it smaller along each axis. click and drag the arrow to move the whole thing:

http://help.autodesk.com/view/MSHMXR/2019/ENU/?guid=GUID-795CC791-2F63-42FC-B58A-B688C5970CE9