[Martin Raynsford] wrote a program that converts a black-and-white 2D image to G-code so that his laser printer could then etch the image. Not satisfied with just that, he used his laser printer ...

The ability to efficiently convert targeted A•T base pairs to G•C could therefore advance the study and treatment of genetic diseases.

If you eliminate the need to convert an existing 3D model, and create G-Code directly, you gain a lot of design freedom, at the cost of increased design effort.