Remeshing of hard surface objects - how to acheive better results with low polycount?

[LiliX]

Hello! I have few questions about Z-Remesher and remeshing hard non-organic surfaces in common. As I’ve got already ot works fine for bodies and curved objects, but what about hard edges? Recently I wanted to remesh several 3d models of furniture like sofas and cupboards and I noticed Z-Remesher smoothes such objects or produces much more polys than I pointed as desired polycount. For instance, here is a model of sofa, which was converted from 3ds to OBJ with a rather bad triangular grid. It is rather low-poly (about 9000 polys), but the grid needs to be corrected through remeshing for further UV-Mapping.

When I load this model in ZBrush as a whole (it consisted of many parts and I had to weld it), I point the polycount as Same or as Half with Curves = 100 and Adaptive Density, but after remeshing I get the model with higher polycount than 10000 polys. Few times I managed to get about 6000 polys but the model was noticeably distorted . I think it happens because the sofa consisted of many parts including hidden (it was made in 3D Max initially) but when I try to import its parts and remesh them one by one, Z-Remesher produces new parts with higher polycount than I desire, all the same.
Few times I tried to use Dynamesh to weld all this parts into one shell, it seems to be better idea and the shell produces more accurate shape of the sofa, but it’s extremely hi-poly (more than 115 000 polys) and when I remesh it, I cannot achieve my desired polycount (about 5000-6000 polys), it remains much higher. Here is the same model after Dynamesh - what to do next to get any good remeshing results?

How to use Z-Remesher for such objects to get mid-poly and low-poly meshes and to keep good accurate shape of the model and hard edges when needed?
Moreover, the same problem arises with models from Scetchup like swords and houses, where exporting to OBJ gives very low-poly models with very poor triangular grids. How to remesh then and avoid smoothing hard edges?
If you tried it and get any suitable results, i would be VERY MUCH grateful for your advice! Retopology has always been my heel of Achilles and I hate to it manually.

Attachments

[Spyndel]

First of all, upgrade to the current version of Zbrush. ZRemesher 2 is much better at keeping object form even on the default settings for objects with harder edges. The upgrade is free for registered users.

Secondly,yes, you will need to fuse the mesh into a single contiguous mesh first before ZRemeshing. ZRemesher does not fuse separate mesh objects. It only retoplogizes them.

It’s a complicated subject. Generally, a hard edge should be considered a fine detail like skin wrinkles when remeshing. You will need to subdivde the resulting low poly mesh, and project detail from the original onto it to recapture fine detail, and exported like any other fine detail in the form of normal and displacement maps.

There is, sadly, no magic button to magically create completely accurate super low poly geometry for hard surface objects, as accurate as a person would, for creasing edges. If you really need that, you should model the object from low poly, or manually retoplogize and draw the edges in deliberately rather than use Zremesher.

However, for an object that is mostly organic like the one in question and doesn’t need super crisp edges and machine perfection, you can try increasing the adaptive slider value in the ZRemesher menu. This will make it more accurate in form at the expense of polygon shape. You can also try using the polypaint feature in the old Zremehser to paint edges to receive more detail at the expense of areas that dont, to keep polycounts down.

Zbrush 4r7 has more options for this, but this is all I can recommend for the out of date program version.

[MentalFrog]

Do you use other 3d software packages, 3DMax, Maya, Blender?

It looks like you’d be better off converting the tris to quads in a real 3d program and then bring it into Zbrush.

Zremesher is like a little kid throwing a tantrum. It won’t listen to you and does what it wants not what you want. In other words it ignores half your inputs and just throws out whatever it feels like. So far I’m extremely frustrated with Zremesher on organic models and trying to get it to do what I want. For an automatic solution with manual inputs it sucks, it needs a lot of tweaking.

[LiliX]

Do you use other 3d software packages, 3DMax, Maya, Blender?

It looks like you’d be better off converting the tris to quads in a real 3d program and then bring it into Zbrush.

Oh, yes, I tried detriangulation in Maya before Z-Brush, but all the same it leaves quite a few of triangles in many spots and I don’t like all the geometry of the model in general. Because this model and many others was made in 3D Max, it consists of many separate parts, including invisible inner parts under the seat, what increases the number of polygons. If to use such models in render scenes as it is, it prolongs the render time, so for me it’s rather to make this model a whole piece without inner parts and I found Dynamesh to be the best tool for this purpose. But the whole shell after Dynamesh needs retopologizing, of course. I’ve read somewhere that 3D Coat may be the better tool for retopology of hard surfaces than Z-Brush and even can make it automatically, but so far I played with its trial version and couldn’t get any suitable results, 3D Coat seems to be purposed more for manual retopology. So far I found that smaller adaptive values (about 20-25) produce larger polygons and it lessens polycount a bit. At least, I feel I’m on the right way.