Bend any retopo mesh along curve -> get retopo geo

[poeboi]

Warning: This is not a 100% reliable, completely fault proof approach. In some circumstances, the "quadrangulation" on the re-imported mesh to modeling room from sculpt room will not be completely like the original, and some manual fixing might be necessary. I discovered this after some subsequent testing, models which've been bent a lot seem to not get their topology back 1:1.

You have an object in your Modeling or Retopo workspace.
It is retopo geometry, so quads or mostly quads.
You want to bend it around a curve, but still preserve retopo geometry, so quads not triangulated.

For example, you modeled a character belt "straight", you made curve cross-section of character waist, now you want to bend the poly model belt over character's waist.

Workflow:

1. 
Modeling / Retopo Room  
Of object to bend, make sure longest side points in direction world up (default Y+), shortest side in direction X+
-> goto Sculpt Room 
2. Space to bring up tools, select Import tool. Select Pick from Retopo to get your object from Modeling or Retopo room.
- Make sure
✅ Import w/o Voxelization
✅ No subdivision more than what you had
✅ Sculpt Tree layer to import to is "S" as in Surface Mode

3.
Create Curve you want to bend to.
(For example, make Cut Slice over object and produce curve from that)
With object to bend in Sculpt Tree as selected Sculpt Tree layer, RMB on Curve, choose "Bend volume"

Observe model is bent along curve.
Adjust parameters to taste.

RMB curve again when satisfied, get the Bend Volume modifier's options, select "Detach Curve Modifier".

By this point you should have your bent model, except it's tris.

4.
RMB on the Sculpt Tree layer with your bent mesh (Default name: Curve_CurvedBend, name produced by the bend tool)

Select Retopo via decimation 

For the dialog box select "Don't decimate"

Observe you get your bent model, still tris, as a new occurrence of item under Poly Groups

5. 
Select all faces  of the Poly Group

Title bar menu  : Mesh  -> Apply Quadrangulation

Your model should now be quad like the original, unbent retopo mesh.


(Bonus) ABOUT GETTING UVs back
I can not just yet speak to whether you can also get UVs from this process, since I haven't tested yet

But you might be able to get the UVs if 
1. You export the UNBENT object with correct options first, and then
2. With new occurrence of bent object, import UVs that you used for your original

Or possibly if you
1. Unwrap the bent object
2. Copy-paste UVs of original, unbent object.

Edited March 30, 2023 by poeboi
warning