I forgot to mention that it’s recommended to turn on History recording so that any eventual modifications of the original curves could affect the projected curves or the extruded surfaces with intersection curves.
Interesting that nobody mentioned the ‘shut lining’ feature in rhino? This makes the panel gap modelling much simpler and you can amend back and forth in a more flexible workflow.
Shutlining only modifies the display mesh. It does not change the geometry.
https://docs.mcneel.com/rhino/7/help/en-us/properties/shutlining.htm
I have tried shutlining in the past and got mixed experience with it. I much prefer to use curve intersection between the car’s body and some editable surface that intersects with it at a controllable angle, as explained in post #16. It’s a very powerful way to find the best possible shape for the panel gaps when it’s combined with Rhino’s History. I usually hide the geometry of the intersection surface with the ! _SetObjectDisplayMode command and selecting “Wireframe” mode so that I can see the car itself and the control points of the surface that I can move around to control the shape of the curve intersection. Also, I always need separate body panels, so the NURBS geometry itself needs to include true panel gaps with fillets.
Oh yeah I know that; but it gives the option to at least have a look, and regardless you end up with the curves on surfaces to eventually pipe or fillet the final geometry until your wrists begin having nightmares.
Plus, you can extract that render mesh for rendering or rapid prototyping if you wanted.
@Rhino_Bulgaria , you could do your surface intersect trick and use the curve in the shutlining command. Plus, if you use it and find some bugs, maybe it is a tool that can be improved! Those mesh modifier type ones are in need of some love, if you ask me.
I may give it another try in the coming days, though I’m perfectly happy with the basic curve intersections. 
For manufacturing purposes I always use NURBS geometry, so it’s mandatory for me to have a proper NURBS polysurface model.
you and @AlanMattano need to become friends.
I’d love to see what that superfirends mashup would create.
feeding this exact image to one of the AI render engines like vizcom may yield some fun stuff.
Back in 2023 I used to play a bit with some of my old drawings on “Vizcom”, but honestly I prefer to rely on my imagination when it comes to car design. I would feel ashamed if it’s not my own creation. I stopped using AI after that brief experiment.
Here is one example with a drawing that I sent to “Lamborghini” back in 1999. The name “Диабло 2” written in Bulgarian alphabet translates as “Diablo 2”. That was a couple of years before the introduction of Lamborghini Murcielago in 2001.
The L/R arrows on the door and the words inside the brackets on my drawing mean that the car needed a longer wheelbase which should be extended in that particular area. I asked “Vizcom” to make a longer wheelbase and it failed.
Even though “Viscom” added some nice 3d-like effects, the general quality was not satisfactory. I expected realistic paint and panel gaps - just a smoothed out version of my drawing, but the program returned pastel-like effects with lots of random artifacts. Especially on the wheels. Perhaps it was not developed so well 3 years ago. I also expected it to take in consideration the specific aerodynamic shape of the rear wheel arch, but instead it chaped it like a regular one.
I see lots of shiny AI car images nowadays that are way better than what I was able to achieve with the program at the time. Plus, the paid version of “Vizcom” had more tools and ability to apply AI over select regions of existing AI image to further improve it.
Edit: Here is what “Vizcom” did with this particular rendering of Audi Avus Zwei. No idea why it decided to apply a classic “Jaguar” grille in the last image…
