ZBrushCentral

symmetry in topology mode

ZBrush Usage Questions
#1

Symmetry doesn’t work for me when I try to retopo a model (works, but not well), I make sure it’s enabled, I do my work on one side of the model, then I look on the other side and it’s hafl-screwed up, if I click to delete a point on one side the point doesn’t get deleted on the other side, anyone know what might cause this?

Thanks.

#2

Your reference model could be slightly asymmetrical or off center. Sometimes, you just miss a connection target somewhere along the line, and it messes up work you do subsequently. And I’ve noticed that ZB does much better when there is a clear centerline down the middle.

In either event, dont worry overmuch about it. Once you complete the mesh and generate the skin, its a simple matter to resymmetrize it with Smart Resym, or the new Mirror Weld function.

In the meantime, In the topology palette, set Max Strip length to 4. This will let you see explicitly any missed targets or Ngons, as it wont “connect the dots” unless your polys are exactly quads or tris, and you’ll see a hole there. If set higher, Zbrush will attempt to fill in those gaps during the preview, and you might not detect problems until much later.

#3

Before retopo’ing try running resym or smart-resym to ensure your model is perfectly symmetrical. If retopo goes awry on the mirrored side of where you’re working, the easiest fix is to turn off symmetry and correct the broken side. ZB is pretty sensitive to perfect symmetry for re-topo. I find that sometimes I also have to to use s.pivot command (transform tab) to ensure that pivot ends up in the perfect center of the model.

Alternatives:

1. Draw out on your model (e.g. paint) the lines of your topology. Don't use the symmetry function at all when you build your new topology. (It's not really as much extra work as it sounds since the retopo step is really just tracing your mesh with the topology tools--once you get some speed with the tools it goes quick.) Use smart resym to clean up then project your mesh onto the new base mesh. ADVANCED. With symmetry off, create only one-half of your new topology. Using 3.5's tools or other tricks (such as duplicate, mirror, and merge visible) flip and weld a copy of your half topology to make a perfectly symmetrical topology and project your model to it. ADVANCED. Use an external tool such Topogun or Silo to build your new topology and re-import the new topology. I usually export a level somewhere around 100K or less polygons (typically level 3 or 4 for me) to act as a guide for building my new topology in these tools.

HTH,
-K

#4

Thanks for the reply, for testing purposes I tried retopo’ing the demosolider (assuming it’s as symmetrical as possible) even so, I used smart resym to be sure, 90% symmetry points found (I noticed no matter how good you work no model is 100% symmetrical, is that normal?) I did try to split the model in half, retopo that, clone it and flip it, merge it with the other half and retopo the midline since it was slightly off center but it still didn’t work 100% EX: one poly connected to the midline was missing on both sides because that part of the centerline was missing so naturally if you connect it both pollys will show up, but one doesn’t so it’s still weird. Yes I do not allow ngons on my meshes, not even tris.

I’m using ZB3.1 btw.

#5

I used to have problems with a lot of broken symmetry during retopo. I have far less now…almost none. I am unsure whether 3.5 is simply better in this regard, or it affects certain workflows more than others and after a lot of experience with the process, Im simply better at doing it. I suspect it is a combination of both.

In any event, you should upgrade to 3.5R3 (Im assuming youre on PC, otherwise you would be using 3.2). Mirror Weld is kind of awesome.