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Please help a newbie with dynamesh subtract and addition problem?

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#1

Hi guys

I’m super new to Zbrush. I just need to do this very simple operation but I’m not sure what I’m doing wrong please help?

I’m making a head cap for a ball jointed doll, here is a picture of the Head Cap (which is a dynameshed subtool):

Before Boolean.png

On it I have some cylinders which are just made by appending cylinder subtools from primitives (I haven’t dynameshed them yet). 2 of those cylinders which are nestled inside the extruded part of the head cap are meant to be subtractions, the 3 other cylinders I am hoping to fuse onto the walls of the head cap.

I tried fusing the 3 cylinders onto the head cap first by:

  • making sure the headcap subtool is at very top
  • put the additive cylinder right below it, changed the double moon icon to the left one (to indicate additive).
  • click merge down
  • click on Dynamesh

But the result I get is this:

After Boolean.png

You see how the concave part of the head cap is suddenly just filled? I don’t want that. I just want the cylinder to stick to the side of the wall… why is it filling up? It thinks that the head cap cavity is some sort of hole all I can figure… so how do I stop it from doing that?

I thought that maybe I should go down to “Preferences”, then under “Geometry” - “Close Holes” I should slide the setting to zero. I tried that but what happens after I redynameshed after that is that my head cap now has lots of tiny holes like it was perforated!

Perforated As FUCCCK.png

Do you know why this is happening? And what can I do to achieve what I want to do?

Also, okay now I tried the subtraction boolean. Here were my steps:

  • making sure the headcap subtool is at very top
  • put the subtractive cylinder right below it, whilst it’s selected i went down to Geometry, then under Polygroups I clicked on “Group as dynamesh sub”, then on the subtool pallete itself I changed the double moon icon to the middle one (to indicate subtractive).
  • click merge down
  • click on Dynamesh

But omg!! Why is it filling up the hole again??

Head Cap after boolean.png

Please help… It’s been weeks and I can’t solve this…

#2

Here is something you can try, make sure the vertices are welded on the subtoosl you are going to boolean. With a subtool active, use the Weld points command to weld that subtool. I believe its in the, tool / geometry/ modify topology pallet. If that does not help look at the parts carefully to check if the meshes have no defectes.

#3

Hi Susan

Thanks for your reply! I tried the “Weld Points” thingy, but it didn’t make a difference, upon re-dynameshing, all holes are closed up.
I’m thinking the fact that the cap was perforated above seems to suggest (like you said) that the mesh maybe have some unclosed vertices, but my structure is so complex with more than 4 million polys I can’t possibly manually fix each edge and vertice. Is there a more automated process I can do in Zbrush to retopologize the mesh without losing resolution of what I currently see now?

#4

You’d find this a lot easier if you upgraded to 4R8. It’s free to registered users.

#5

Other tools to retopo the mesh are Zremesher. You could play around with those.
Try and use a CAD package Rhino, Blender ect. that have some mesh analyzing features that will help you see defects in your mesh.
There Is probably something about your mesh that is not allowing a correct boolean. Thats my guess.