the main question is: do you want to store changed textures or not? if so external textures are another nice task, as ofc you'll have to overwrite the external files too (without changing the file format).

If changing textures is not needed there is no real problem, as you can just take the data from the "old" model/terrain.

And what if I procedurally generate a texture and want to save it as external DDS?

To me it _is_ a problem.
I look at this the other way round:
I can change the format of a texture and save it with pixel_to_vec and pixel_for_vec without problems.
That's probably a slow function, because it re-paints each pixel again, but for saving a model - who cares?

There's a source code example for saving HMP and MDL in the SDK - so it shouldn't be much of a problem?

Yes, but we don't know how to read all necessary information from an entity, like, triangles (connected to which vertices), 1st and 2nd UV map coordinates, groups, and so on.

For the triangles, have a look at ent_buffers.

Uh, I heard the first time of ent_buffers... thanks!

ent_buffers is the easy method. The other possibility is loading the model not with the engine but with the MDL7 SDK, but of course that's a lot more lengthy and complicated. Best go the quick and easy way first.

If there is anyone who is willing and able to code an export function for an mdl, please contact me to discuss the conditions and timeframe for that.

Me, myself, I am very interested in learning how to do it, but I have no time for this for now.

I don't mind to pay for a solution, even if it shall be open to everyone in the community.

I prefer a solution that is as lucid as ventilator's obj-exporter, because I could learn from it.

if the time does not matter for you, i can write a pretty clean code in the next weeks (not longer than a month), as i'm implementing a resaving feature atm for my editor. Though at the moment i'm working on the wmp files, and not on mdl files ==> Will need ~2 weeks to start that. If you need it earlier, a small payment would be nice - otherwise without a timeframe - i'll release it open source - but again please don't held your breath - just remember me of this topic in ~2 weeks