I know this is an old post, but the other day I needed to make some changes to this model and was having the same troubles forming clean mess. so after trying a few different processes , I end up with a clean mesh. So I thought I might update this post :) hope Michael can verify if my procedure works or was just fluke.

quick recap... Have a solid I created from a surface, created by Zsurf. has 1000's of points and would not Boolean union cleanly with an other solid (shield shaped solid) .

http://moi3d.com/forum/messages.php?webtag=MOI&msg=5112.1

Now what I did was place the eagle on the shield in it final position.. I then cut the shield and eagle into quarters... using Boolean merge made 2 cuts one along Y the other long X .

this felt me with eagle and shield each cut in 4 pieces. I then boolean union between each piece of the eagle and shield , this felt me with 4 pieces top left, top right, bottom left, bottom right , then I union the two top pieces so MoI only needed to work along 1 edge... then union the bottom 2 pieces.. again only 1 edge in play... then union top and bottom together again only 1 edge in play.

This seemed to work well, I was left with a nice clean solid. no strange internal surfaces.... But from now on , If I need to make any other changes I need to use trim. ie when I wanted to add a cufflink post, I needed to trim the post on to the base . trying to boolean join resulted into a mess a gain :) So I'm guessing when I use trim, MoI is only having to deal with the contact between 2 surfaces and not the whole object. ?

Hi Steve, well it is true that Trim is a kind of lower level operation that does less work than booleans, and sometimes you can get things done with Trim where the booleans are having problems.

But I'm not sure if that was why you had success this time or not, that ZSurf generated surface is mega complex and previously when I looked at it, it seemed like things might be running into some refinement limits in the geometery kernel, like giving up when attempting to generate an intersection curve when it gets over some particularly large control point count like 100,000 control points or something along those lines.

Those sorts of super complex single surfaces are not that common in CAD usually so the geometry kernel has not really been tuned up to work on those kinds of things so much.

It could probably help to simplify the surface at least somewhat, like use half as many sample points on it or things like that.

- Michael