How do I UV unwrap a mesh with over a million faces for texturing with Blender?

I’m very new to 3D modelling. I just want to be able to get stuck in with painting my model but I can’t figure out how to UV map it. I’ve haphazardly UV mapped much simpler objects, but with this model I ended up with a ludicrous number of faces. I can get the number of faces down to about 30 000 by decimating without losing too much detail but then the model loses it’s nice organised loops and ends up random mess and I can’t loop select to put in seams. It’s my first attempt at using sculpting and making a head and I’m excited to paint in the skin details.

I literally only started learning to 3d model last week. I usually work with oil paint, glass, metal and do a bit of papermaking so this is all really new to me. :S

I’ve spent a good few hours looking around for solutions but I’m probably typing in the wrong thing because I’m not familiar enough with the terminology. I’ve just been working through tutorials on youtube to learn this stuff. At the moment the safest thing to do other than starting from scratch seems to be to learn how to generate normal maps so I can work with a very simple mesh instead, but that can’t be the way that this is normally done, can it?

I’m trying to add the 27mb decimated file but it acts like it’s uploading for a while then just stops, so I can’t share it. Sorry.

Any help would be most appreciated. Thanks.

How do I UV unwrap a mesh with over a million faces for texturing with Blender?

You don’t.

Reduce the poly count by retoplogising the mesh. This is really decimation in a controlled manner. You can then create displacement and/or nomal maps to recreate the high detail or use the shrinkwrap modifier and additional subdivision to ‘project’ the lower res mesh (unwrapped mesh) onto the high res original.

Okay. Thanks!

If you were starting with a simple mesh and used a multires modifier and subdivided with that as you added complexity to the model, could you then save it, and then roll it back to less subdivides and use the simple, rolled back mesh for the same purpose to avoid having to re-topologise?