# Invalid body when using "offset face" on a dome

Hi all, I’m new to Shapr3D (and 3D modeling in general). I’m trying to extrude a moderately complex shape on top of a domed surface, but I keep getting the error “Operation failed because the resulting body wouldn’t be valid” (screenshot attached). This happens in both directions (cutting into the dome as well as pushing out from the dome). I’ve tested and extruding the shape on a flat plane works fine. Any idea what could be causing this, and what I can do to fix it? Thanks!

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Extruding a projected image on a curved surface can be tricky.
Here’s a workaround.
Make an extrusion of that complex shape whether on a flat surface or via a sketch. Embed the extrusion in the curved surface and do a union. But, before you do that, create an internal curved surface that is some distance away from the original curved surface. Use it to subtract it from the complex shape extrusion after the union. This way the surface of the extrusion will be a uniform distance from the curved surface. Hope I was clear. If not I can show an example.

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This worked perfectly! Thank you

Here’s another little tidbit. Whenever you use extrude from a Projection, the extrusion is normal to the surface. Here I simulate that ‘normal’ projection using the method I initially suggested above of a separate flat surface extrusion. Using Scale on one face can give you that look. Do it this way if the result is the desired one.

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Thanks @TigerMike . I am using extruded texts a lot and when using it on a non-flat surface I always extrude the text outside of the body, move it in to the body, subtract the non-flat surface from the text. Then I move the text into the body, subtract the body from the text and then move out the remainder of the text a bit and Union that with the body. Leads to a text that perfectly follows the surface. But I never thought of using the non-uniform scaling to make it even more perfect. Fantastic idea.

You’re welcome. Note that I did indeed use ‘Uniform’ scaling. Selecting only one surface will distort the body to conform to the scaling effect.

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