Do I always have to add edge loops to my low poly assets?

crad

Do I always have to add edge loops to my low poly assets before importing them to zbrush? I was happy with a cupboard model I did and wanted to add some details but it completely loses shape when I add more polys in zbrush. I guess I should only ever start from High poly to low poly workflow from now on? As low to high is never working...

Obscura

Yes subdivision works like that. You can try subdividing without smoothing but youll end up with an angular highpoly mesh that you cannot smooth with a smoothing brush. And yes people usually do it the other way. Kinda... Make a lowpoly as a base of your highpoly. When it has enough detail and ready to subdivide, make a duplicate and save it for later. Continue working on the highpoly. When its done make some adjustments to the lowpoly so it matches the highpoly. Some zbrush worksflows would allow you to only work with one mesh and have the lp as a lower subdiv level, but this rarely works with game art and more used in films, since game ready assets has special optimization needs and the topology is different from the hp in most cases.

Ghogiel

Yeah mostly concentrate on the high poly, but those lowpoly shapes and topology, a decent amount of which can be used in the final low poly, aren't useless in the creation of the highpoly either.

Instead of just adding edgeloops though (at least, if you are only adding them in a way that's simply designed to hold shape for subDing), you'll just end up with lots of loops tight right on the edges of the model and non even distribution of squareish quads. Which is not an ideal surface to scupt on. So you either account for that and add them manually, which means adding a ton of evenly spaced loops intersecting the edge control loops some other way. Or you might as well just end up running remesh in maya or zremesh+polygroups, or dynamesh+project etc, to actually keep the base models shape but have a sculpt friendly topology as well to make it simple. In the end the high and low poly topology have different needs and purposes.

Another way to avoid using edgeloops to hold a model together when subDing is using creases in Zb or opensubdiv it with creases. Which also avoids adding edgeloops for the most part. But again, that alone won't surely give an evenly distributed quaded surface that's good for sculpting.

rollin

As usual it depends but I would say +1 for creases (where applicable) as they are less intrusive as edgeloops 

DavidCruz

Try to add in loops that would be helpful, i guess planning ahead here would work best, so you like the current shape, save a copy of that one, add in the loops and then check how it subdivides, if it works for you export that version to zbrush and you would have a decent version of each.  
I used to do this back in the day as an example (low to high,high to low same meshes), job was to zbrush / texture was already unwrapped and wanted to do it very quickly so i just subdivided the model with no smoothing and smoothed until i was happy, worked out at the time so its possible i guess.  Do not do this anymore tbh though but i think if you are doing things for environments and the lowpoly is the final version you can get away with it, maybe not so much with sharp objects, or you can just add an astronomical amount of subdivisions if your pc can handle it then the oddities won't be noticeable. 
Good luck.