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enter image description here

The effect I'm trying to achieve in the image is an inset panel line on a model destined for 3D printing. The panel line has to be part of the mesh, so that the negative detail will show up on the physical model (So alternative methods of creating superficial panel lines are useless).

But, after extruding along face normals to create the neccessary depth, I've hit on this snag:

What is happening in the pic is that because the overall object has faces of three distinct angles, the inward extrusion is fighting against itself to extrude evenly, and the subsequent faces of the panel line trough are non-planar. Which is not ideal for 3D printing.

What I want, is for the extrusion to 'cut' the same profile, but with each trough face planar relative to the object face it's cutting into.

The tutorial in the below link, message #6, demonstrates exactly what I want to achieve, and I understand what they're getting at. My extrusions are not co-planar, because they're extruding on face normals.

https://forums.scifi-meshes.com/discussion/79844/blender-starship-modelling-techniques-especially-enterprise-variants

But, following the tutorial instructions (Extrude with offset 0, then shrink/fatten vertices to required depth) gives me exactly the same result. The below pic demonstrates what happens (In reverse, an outward instead of inward extrude). Notice how the extrustion kinks forward because it's following the normals, and creates a twisted non-planar face.

enter image description here

Could anyone either tell me what I'm doing wrong, or perhaps suggest a better method of creating panel lines in the mesh, that doesn't create non-flat/non-planar faces? Because I'm STUMPED.

EDIT: The whole object, showing the various angles (created by the knife tool). The panel line is towards the tip, after the Y-axis kink.

enter image description here

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  • $\begingroup$ At this point the only way I'm going to be able to help you is if you add your blend file to your question so I can edit it directly. (Grab the URL of the question. Go to blend-exchange.com. Select the blend file. Add the url of the question. Grab the url that results. Go back to the question and edit it. Add the new url to the bottom of the post.) $\endgroup$ Aug 15 '21 at 13:47
  • $\begingroup$ Thanks Marty. Unfortunately, blend-exchange appears to retain the right to distribute your file after upload. As this design might end up being sold, I can't upload the file. But I appreciate your offer to look further. $\endgroup$
    – Aethon
    Aug 16 '21 at 22:06
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Is this it? Or, maybe a step away?

  • E Extrude and right-click, drop in place
  • SShiftX or whatever axis is perpendicular to the extrusion's walls

enter image description here

For an even, rather than a scaled offset, you could then use GG Edge Slide, with the E Even option?

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  • $\begingroup$ This is inwards, but out is the same.. $\endgroup$ Aug 15 '21 at 20:54
  • $\begingroup$ That looks promising Robin, thanks! I've tried a similar method, but because my design is angled on all axis, it's creating some odd normals. So basically, I can't omit any axis with S-shift-X/Y/Z because, annoyingly, all of them are required to scale the multiple faces. $\endgroup$
    – Aethon
    Aug 16 '21 at 22:10

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