3d circular interpolation

Hi,
I wonder is there any way to make 3d circular interpolation?
If I try something like this "G02 X1 Y1 Z1 I1 J1" I will have a "2.5d" circular interpolation. In both x and y axis it will be circular but in z it will be straight line interpolation. Is there any way to make it circular in all axis including z.

I am looking for that to improve my inkscape plug-in wich uses circular interpolation for flat curves, and I am thinking of invoking new function that will provide non static depht cutting.

Gcode is limited to arcs in xy(g17) zx(g18) and yz(g19)

linuxcnc.org/docs/html/gcode_main.html#sub:G17,-G18,-G19 :

sam

This is one big reason the 3d CAM packages are popular... it takes a LONG file to get complex curves.

Thanks a lot!