Creating shells / cutting up original mesh without changing geometry

[arumiat]

Hi there!

I cut out & thus create ‘shells’ from my game objects that I then use in Unity as a ‘selection mesh’ to highlight an area in-game like so:

The orange highlighted area is the shell.

At the moment my workflow (for a single shell as an eg) :

• I take the original low-poly object
• I subdivide it ( I actually use a subdivide macro that subdivides without shrinking )
• I then mask the area I’d like to create the shell from
• create a polygroup
• use grouploops to smooth out the edge
• split this polygroup to a new subtool
• I then project this shell geo back to the low poly mesh
• I then decimate this shell geo to make it game engine friendly
  However unfortunately the shells often don’t match well with the underlying geo so the shell looks messy in Unity.
  

I was wondering whether there was a different workflow that I could use to create these shells… perhaps a way to cut the original low poly mesh smoothly… At the moment I have to subdivide the original mesh, in order to be able to paint with the mask smoothly to select the relevant area.

Any ideas would be appreciated!

[Spyndel]

If you are cutting or fusing geometry, some change to the topology is inevitable. I can’t speak to your process. I am not familiar with what you are trying to do, or why it is so complicated. There may very well be an easier way to go about what you are trying to do.

For instance, why can’t you simply duplicate a 2d section of polygons to act as your “selection mesh”? That would create an exact duplicate of the underlying topology and fit perfectly on top of it? I don’t require an answer to this question, only using it to point out that I don’t really understand what you want.

In any event, Live Boolean can be used with cutting objects to cut out pieces of geometry, and it will only alter the geometry where it intersects–edges will be inserted to force quads and tris at the border, but nowhere else.

Good luck!

[zber2]

Hi @arumiat

Also, you can simplify it much more and get much better results if you use a Mesh Project brush.

[arumiat]

Thanks a lot.

I don’t really understand what you want.

I’d like to create shells based an original model that occupy the exact same 3D space as the original underlying model (as much as possible)

why can’t you simply duplicate a 2d section of polygons to act as your “selection mesh”?

If I’m understanding your suggestion, if I only duplicated the polygons I would end up with a selection mesh that has ‘stepped’ / jagged edges? So the selection mesh in Unity would end up like the yellow selection (and I need something like the green selection) :

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The Live boolean sounds interesting but I am unsure how to ‘paint’ the selection that I need, which is sometimes quite intricate, by using another object. Is there a way to use LiveBoolean with masking somehow? I can only see videos on how to use another object to create an intersection.

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Re the MeshProject tool, - cool! I played a little. I tried to create a ‘shell’ ( that in fact isn’t a shell at all as it occupies exactly the 3D space of the underlying model ) and the closest I got was
Zintensity 0
Brush _> Depth → Imbed 100

However it leaves a gap in some regions and smoothes ‘into’ the mesh in other regions.:

Is there any way to make the new mesh created follow more closely the underlying mesh / occupy exactly the same underlying 3D coordinates?

[tobor8man]

@arumiat - perhaps this video from Michael Pavlovich (always a great resource!) on ZProject/MatchMaker Brushes might help. Note also that he uses the Topology Brush at the start to create a base mesh which he subdivides and projects to the surface. Seems like the Topology brush might be useful for your use case. Also look up History Project Brush (more recent Zbrush builds) which has some advantages over the ZProject brush.

In many ways it seems like you want to “retopo” your model in select areas, so perhaps look up MikePav’s videos on Zmodeler retopology. You could create specific subtools with controlled topology in the patches you want with the Zmodeler extrude (retopo) tools.

Good luck.

[arumiat]

Dear all, I appreciate your help.

I managed to make nice ‘shells’ / cutouts quickly using the Mesh Project brush using symmetry and also sometimes live boolean so I could draw from different angles. One issue for me is though they often have overlapping vertices like this:

I have tried dynameshing but it turns it into a two -sided mesh with ‘cheesy’ edges.

I would ideally like to keep this one sided mesh, with clean geometry & a reduced polycount.

Do I have any other options?

[zber2]

Hi @arumiat

@arumiat

I would ideally like to keep this one sided mesh, with clean geometry & a reduced polycount.

Do I have any other options?

Dynamesh does not work very well on thin meshes. It needs more thickness / volume to work well. If you want to reduce poly count, your best bet would be ZRemesher.