PixelPest

While Garry´s method will end in an infinity loop path you might consider to break the "Pie" at the middle point and delete after converting to Curves:

Unfortunately this can be quite cumbersome as you´ll need start+ end points at the top row alternated - from there it´s just a few clicks:

I can't help it if the work is already done. I said: "I´d make a shape for the face for instance and put any content/detail inside (masked by the shape) and the shadow shape at first in the hierarchy with either transparent grey or/and additional blend mode." In the case of the example screenshot from @BenjiGameDev I´d draw a snapping/transparent/multiplied shape on top - no big deal really. In case of vector graphics planning has always been part of the process methinks.

It don´t need to match - it´s masked by the "head path" und just got a little amount of "Gaussian blur" along some transparency and "Multiply" blend mode.

I´m not under the impression to need any workaround here:

I´d make a shape for the face for instance and put any content/detail inside (masked by the shape) and the shadow shape at first in the hierarchy with either transparent grey or/and additional blend mode.

I was misdirected by your example.

A Compound Path (hold alt-key while Boolean-add) may work for you then: Cheers

When you look at my GIF from Aug 5th you´ll notice that this step isn´t necessary.

I got SV2 for 99ct at an offer, but still prefer Inkscape over it. You can get it for 20 bucks at StackSocial I believe. I´m not advertising here! Regarding XQuartz/Inkscape: see my note 3hs ago.

Just one last from me on this topic as I literally live in Inkscape and Intaglio; Inkscape1.0 will get an additional centerline tracer.

Actually the user defines quantisation and other parameters:

I believe you could have asked in the 3d forum of your choice. Cheers the plunger

Was just asking because it just traces one color/value at the time.

Have you tried that?