FYI in the Automotive world on vehicle car bodys, the 3D CAD data will have a blue sphere with unique code for the location for a RSW(Resistance spot weld) this denotes a two thickness weld i.e. two panels welded together. Then there would be a Red Sphere for 3 thickness RSW welds. Never 4 Thickness welds as bad resulting in potential issues with weld failure, unable to predict if the weld nugget forms correctly.
For CO2/CMT welding there would be a blue cylinder the length of the weld required on the relevant assembly for the BIW line to show the welders to put it. The points for the RSW would automatically be fed to the robots for programing 3D Cad using Delmia or some other such CAD simulation system to optimize paths and speed. Nothing too fancy as most BIW bodys's have around 4000RSW's, sorting weld sequence of sub assembly's can be fun, ideally the body should use only RSW's if steel, but the reality is the assembly sequence causes issues such that you cannot reach a weld so need to use CO2 or use adhesive instead.