It is usually 2D, might look 3D but usually it is paint on walls. That is how graffiti has always been, but it is the most flexible of art forms and as such the idea of making it into a 3D sculpture piece is one that is probably natural and it certainly a brilliant one.
A certain Evan Roth took the idea of creating a sculpture through the form of live graffiti artists, using the 1983 documentary Style to then map tags and then create a physical object form. The sculptures are finished in chrome dipped ABS thermoplastic
Anyways, we like it