ZBrushCentral

Any Way to Reliably Check if a ZBrush Model is "Watertight"?

ZBrush Usage Questions
#1

Hi all!

I’ve been importing and exporting stl files between Sketchup and ZBrush for a few days now, and I noticed that whenever I export the file back to Sketchup, Solid Inspector (a plugin that checks to see if a model is solid or “water tight”) always discovers triangles without faces.

Turns out, some of the triangles made by Dynamesh are much too small for Sketchup to generate a face, resulting a numerous triangular holes. Even if I scaled the model to over 1000mm in Sketchup, the triangular holes are only about 0.1mm, which is too small for Sketchup to generate faces. Sketchup’s Solid Inspector is now unreliable for checking the model’s solidity, since Skethcup can’t even generate a face that small even if they’re actually there.

I used NetFabb Basic to repair and check for holes, and it tells me that the model in question has no holes or border edges, but I’ve heard that it can be somewhat unreliable.

So, is there any way to check if a model is solid/watertight in ZBrush itself?

Thanks for any advice.

#2

Well, you can ensure a mode is completely closed in Zbrush by running Tool>Geometry>Modify Topology> Close Holes on it. But that doesn’t seem to be your problem. From what you say, the problem is in Sketchup not being able to handle the dense geometry, not with open holes in Zbrush.

You may want to use remesher to make more manageable, cleaner, low poly geometry prior to export.

#3

Thanks so much!

I halved the polycount with Zremesher, and it produced some really clean quad topology–too low for sculpting details, but it’s perfect for Sketchup. Just opened the file in Sketchup, and Solid Inspector reports that it’s water tight!

Although, the edges kind of suffered from a bit of smoothing.

Is there any way I can keep them sharp? I tried masking and creasing, but that doesn’t work.

#4

I’m afraid I don’t know much about Sketchup, your workflow, or the reasons you want to work back and forth between the two programs.

Few other programs can handle the polygon density Zbrush does. Typically, that high res detail is made up with normal or displacement maps in the exterior app. But it sounds like you have 3d printing concerns, so that may not be applicable.

Crisp edges created at the high poly level are a fine detail like skin wrinkles that must be projected onto the new mesh topology after subdividing. Normal or displacement maps can then be generated from the object with multiple subd levels. But if that doesn’t work for your situation, then you’d be stuck with another high poly export. It may be that Sketchup would like it better since the geometry is derived from the cleaner base topo, or it may be that Sketchup is just not suited to handle high density imports.

http://docs.pixologic.com/user-guide/3d-modeling/topology/zremesher/transferring-detail/

You may need to re-evaluate your workflow, and determine if you are applying your available tools in the most optimal fashion, or in the correct order. If you need mechanically crisp edges with a low poly count, then those objects should be constructed at the low poly level using traditional polygon modelling and edge creasing. Based on the preview videos, zb4r7 will have tools better suited for this.

#5

Thank you so much for the detailed explanation, Spyndel!

…and I really need to spend more time at the docs page. :lol:

Frankly, so far I’ve just been trying different things out to get a handle on how I can complete a project by exporting between ZBrush and Sketchup–making use of ZB’s awesome organic sculpting tools, while taking care of the hard surfaces with Sketchup’s more intuitive UI. I’ve been using the latter for a few years now, and I’ve been able to sculpt (or draw, in Sketchup’s case) most any hard surface model, and with relative ease. That said, Sketchup is horrible at handling organic shapes, which is where ZBrush excels. The amount of details you can add with ZB using alphas is unbelievable, and the ability to sculpt 3D textures just from a picture is downright insane!

The reason I have to export back and forth between ZBrush and Sketchup is because I need very precise measurements for ball-and-socket joints as well as the size of the model. Among other things, I “customize” actions figures for people, and the joints need to be the right size so they can fit onto the figure they’re designed for. Another example is Transformers toys. A head cannot exceed the size of the hole that it has to fit into between robot and vehicle mode–also the size of the ball or socket has to be exact to fit with the joint or socket on the toy itself. Even if I were to design an entire figure from scratch in ZBrush, the minute clearances between joints has to be accurate right down to a fraction of a millimeter for it all to work. Unfortunately, ZB’s transpose tool isn’t nearly accurate enough for the job.

Hence, the need to export to Sketchup for resizing and finalizing the model for print.

I’ve come to realize that Sketchup and ZBrush are much too different in the way they work to be able to sculpt the same parts of the model consecutively. Basically, I’ll have to minimize any “cross-sculpting” between the two softwares. The only thing ZB has a problem with is measurements. I’ll have to either remesh or decimate the model to a manageable polycount (10k or so) and then export it to Sketchup for resizing. Ball-and-socket joints will be the final parts made in Sketchup so that they’re the right size, and then exported to ZB and merged with the main model.

In short, you’re absolutely right; I really need to rethink my workflow. Or rather, establish a workable one.

If only ZBrush had a more reliable measuring tool, I’d simply sculpt the basic hard surface shapes in Sketchup (because it’s admittedly quicker) and then do everything else in ZBrush. I can’t wait so try out 4R7; the new hard surface tools could be the perfect solution to my problems once and for all. Better still if they threw in a measuring tool!

100% made in ZB = no headaches. :lol: