Dynamesh with subtraction problems

[kyphur]

I thought I had figured this out but it’s popping its head back up again.

I’m prepping a model for printing and trying to use the dynamesh subtract function so I have certain parts that can be printed separately. I’ve tried numerous attempts with different methods and all the same. It only adds it to the existing mesh.

One of my step-by-step processes:

1: The object I want to subtract I select in the subtool, group as polygroup subtraction, turn the second icon on for subtraction.

2: The subtraction subobject I will usually run the “close holes”, “merge triangles”, “weld vertices” and “optimize points” just to make sure everything is solid and good to go.

3: The primary object I will do the same as step 2.

4: I will group it as a single polygroup also to make sure there’s hopefully no confusion from Zbrush for what I want.

5: Merge the primary subtool down to the subtraction subtool and check my polygroups to make sure I still have the subtraction parts still white.

6: Run Dynamesh.

7: See the results aren’t what I’m supposed to have.

8: Curse loudly.

What am I doing wrong?

[Spyndel]

Dynamesh subtraction with subtool merging is a bit fussy. See the following link and follow those instructions precisely.

http://docs.pixologic.com/user-guide/3d-modeling/modeling-basics/creating-meshes/dynamesh/with-subtools/

Key points are:

1. The subtractive mesh must have fewer polygons than the target mesh.

2. The Target mesh must be an active dynamesh object (so turn on dynamesh for both subtools before merging)

3. In the Merging operation the Target mesh must be selected and merged down onto the subtractive mesh. Otherwise, it will result in an additive operation.

Let me know if you still have problems keeping those points in mind.

[kyphur]

Yeah, all those are done.

I used to have problems because I didn’t realize that you had to have the main mesh already dynameshed in order for it to work. Sometimes it would work, sometimes it wouldn’t. That’s when I used the tutorial/wiki that you posted just now. That was a while back and even then I would sometimes have these problems.

I didn’t know about the deal with the polycount needing to be lower than the main mesh. That’s good to know. I really wanted to get this printed before Christmas but it’s just not going to happen it seems. FLeh.

[Spyndel]

Try this.

As long as the previous 3 points are all valid, ignore the little boolean icons in the subtool slot (subtract, intersect, etc), and just merge down the active dynamesh target mesh on top of the subtractive mesh. Then, in the combined subtool, hide everything but the subtractive mesh (assuming you have different polygroups assigned so hiding should be as simple as shift-ctrl clicking the target polygroup–if not do a tool>Polygroups>autogroups function to separate all the objects into distinct polygroups).

Then, with only the subtractive mesh visible, click Tool> Polygroups> “Group as Dynamesh sub”. Un-hide everything and perform the dynamesh operation by ctrl-drag-releasing a marqee in empty canvas space. Note: you must do this twice in succession if there is any masking–once to clear the mask, the next time to initiate the remesh.

The previously specified 3 points must still be observed, but this should result in a subtraction. If it doesn’t, there is something problematic with your subtools, and we’ll need to get a better look at what you are doing. So be prepared to post some screens, and possibly your tool file.

99% of the time it’s a simple user error in the somewhat unforgiving procedure that will seem much simpler once you learn how to reliably do it.

[kyphur]

Done that. I’m thinking the file may just be too much for Zbrush. Hopefully a 64 bit version will take full advantage of my system. I built it just for dealing with high resolution meshes but Zbrush will either poop out with an error (usually if I have polyframe on when dynameshing) or just add it to the base geometry.

[kyphur]

Here are some errors I’m getting. I will also post some images of the sculpt to give you an idea in just a second.

Attachments

[kyphur]

Here’s some simple pics of the geometry…

Attachments

[Spyndel]

Yes, it looks like you are working with two very dense, complex objects. Dynamesh works best in the medium-medium high poly range. It varies by system capability, but it looks like you are being a bit overly ambitious, especially if you are getting memory errors.

Also, I can’t tell from the picture, but the subtractive object looks like it might be 2-dimensional (not a solid 3d object). That is unlikely to work well.

Dynamesh is great for establishing form, but at some point you are going to want to run it through zremesher to establish a low poly base object with cleaner topology, and subdivide so you have an object with multiple subdivision levels to work on before you start fine detailing. See the following article for how to transfer detail to a new mesh:

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

I would duplicate the subtools in question, and remesh them at a lower resolution. You’ll lose some detail, but that can be projected from the originals afterward. Perform the operation on the lower res objects. Make sure the subtractive object is watertight with a decent volume.