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Looking for a way to taper an imported STL model off toward the bottom (or top, if easier). The same transformation would turn a straight cylinder into a cone.

The intent is to make a vase like the model in the image that tapers off so it will fit as an outer layer to my clay pots.

The model is symmetric around the XZ and YZ plane and only has positive z values.

I assume this would require some non-linear transformation, but I'm unable to find results when googling.

Model

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  • $\begingroup$ Consider to provide a link to the code, or if it's not particularly large, edit your post to include it in a code block. It's tough to recognize how you've created this model. $\endgroup$
    – fred_dot_u
    Commented Jan 30, 2023 at 0:23
  • $\begingroup$ It's an imported stl-file $\endgroup$
    – GusOst
    Commented Feb 3, 2023 at 12:56
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    $\begingroup$ I don't know in Openscad. But since the question has been up for a couple of days, would you be helped by how to do it in Blender instead? It would be quite easy with proportional editing with a linear falloff. I can write a full answer if you ad "or Blender" to the question. If I do it now I may get flagged for not answering the question. $\endgroup$
    – Smitje
    Commented Feb 9, 2023 at 22:28
  • $\begingroup$ Sure, very kind! I know nothing about blender and will probably just crunch the stl-file myself programatically. But it could be helpful to someone else I guess. $\endgroup$
    – GusOst
    Commented Feb 15, 2023 at 18:40

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To install Blender go to Blender.org and download the version for your platform.

No need to install just extract and run "Blender"

to enable importing stl files go to edit -> preferences
in the addons tab search for stl, check the box.

enter image description here

Now import your stl: File -> Import -> STL(.stl)(experimental)
and select your file

You may need to zoom out quite a bit because of the scale.
Do this with the mouse wheel, while the pointer is over the view where the part is. Or with View -> frame all

enter image description here

If the part is not selected (it has no orange outline) select it by clicking on it.
And go into "edit mode" by hitting TAB

Now rotate the model so you can see the bottom plane.
Hold the middle mouse button and drag.
If all vertices are selected when you open the model, hit "a" twice quickly to deselect all.
Select the bottom vertices by shift clicking them.

Now comes the actual conical scaling
Activate "proportional editing" By hitting "o" or clicking the icon, and select linear in the drop-down menu.

enter image description here

Scale by hitting "s" and moving the mouse but do not click yet
enter image description here Now hit "Shift z" This will constrain scaling to the xy plane.
You will see a circle that indicates the region of influence of the proportional edit. Adjust it to your linking with the mouse wheel, and click to confirm. Or if you want a precise ratio type for instance 0.8 and hit enter to confirm. enter image description here

TAB to exit edit mode.
Check that only your object is selected. If other objects are orange, hit "a" twice to deselect all and select your object bay clicking.
And finally File -> Export -> STL
Give it a different name than the original check "Selection Only" and "Export stl" enter image description here

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  • $\begingroup$ Since the instructions were so good and blender is less than 200 Mb I gave it a try. Worked a treat! Big thank you! $\endgroup$
    – GusOst
    Commented Feb 19, 2023 at 18:58

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