Yeah, it just uses really high polygon counts. Internally, it probably uses some kind of hierarchical structure, where it has low-detailed polygons which are tessellated to produce the high polygon counts which you edit.
Check out the "topology brush" for some ideas about how this might work internally.
From what I understand, Zbrush is not running in D3D or OpenGL. So the limitations of those technologies doesn't really apply. It is polygons like Hodgman said, but not traditional OpenGL or D3D mesh polygons. There are a bunch of features that bend the rules in Zbrush.
Edit: I can imagine that the insert mesh is done by grabbing the border edge vertices, doing some math to find out which ones are closest between the two objects and drawing lines between the meshes. I don't know what math they use to build the surface triangles between the objects but it is probably some of the math from Dynamesh and/or Decimation Master.
thank you people..
I think they use simple mesh tesselation. in that case topology control is very difficult and some time It break well
I'm good enough check about Zbrush I think their algorithm is not enough. It's good point to I can start.
My aim is adding all feature photoshop, rhino , sketchup, Zrbush. and 3DS max charactor studio and lightscape's renderer.
and my 3D game engine and also 3D printing sevice and tool..
Happilly I already have my 3D game engine and photoshop and very bad renderer hohoh...
so I must make charactor and Rhino function for next 10 years hahahaha..
Everlasting but not making money business for solo work
Beauty is only skin deep , ugly goes to bones
World's only 3D engine tunner and 3D engine guru.
and real genius inventor but very kind warm heart .. and having serious depression for suffering in Korea
www.polygonart.co.kr ( currently out dated and only Korean will change to English and new stuff when I get better condition sorry for that)