I have
Head[outline]
is Graphics
and
Head[foo]
is Graphics3D
When I do
Show[outline,foo]
I get "could not combine ..."
Is this supposed to work? I want the 2d object to be in the z=0 plane. (I;m running Mathematic 12.2)
You can use Texture:
Texture
Graphics3D[{Texture[Graphics[{Disk[]}]], Polygon[{{-1, -1, 0}, {1, -1, 0}, {1, 1, 0}, {-1, 1, 0}}]}]
Also, have a look at Inset.
Inset
Here's a module that converts (some) 2D Graphics to Graphics3D. It works on Graphics which use only the Primitive "Line" ... which happens to be all I need. Maybe Wolfram could finish it and make it apply to all Graphics expressions.
It looks through a Graphics expression (recursively), finds all "Line"s, and makes the defining points 3D.
Well, it runs out that the above doesn't work for more complicated stuff (even if the only primitive is "Line". There are things in the Graphics object that are private to (someone?), and don't work right.
Here's a module that works on the String level, and seems to work as I want (but still only for Line primitives.)