Hi Nick, I was able to get your paws glued on properly using the Trim and Join method instead of the booleans for this case, I've attached a 3DM file with the result.

This technique is something that can be used to get a result out of situations where the booleans are getting confused for some reason - in this case the booleans were most likely confused by the coincident surfaces not being identical, particularly with one's seam running through the middle of the area.

So to use Trim I went to the paw pieces and selected these faces here:



And then just deleted those faces to make those paw pieces be open surface fragments that look like this:



Then I separated out the upper surface of the main body piece that you want to connect them to, and selected that surface and ran the Edit > Trim command:



Then for the cutting objects I selected all the open edge curves of the paw pieces to use as cutting objects. That then cut the surface so it looked like this:



Then I glued all those pieces together back into a solid using Edit > Join to get the attached result.

One trick for the trim stage is that instead of picking all the little edge curves one by one in the stage where you're selecting cutting objects, you can use a script to do it with just one keystroke. To do that, go to Options > Shortcut keys, and add in a new shortcut key (I use N for "select naked edges"), and then for the command part paste in the script shown here:
http://kyticka.webzdarma.cz/3d/moi/#SelectNaked

That allows you to select "naked" edges (edges that only belong to 1 surface and are not joined between 2 surfaces) with the N key after that, it's a handy way to select cutting curves in a situation like this, and it's also very useful for analyzing which particular areas of an object are preventing it from being a closed solid object.

Hope this helps!

- Michael

Geez... this whole thing is becoming a nightmare... the paw is from a pdf (vector) from the mfg. that I projected (direction) to the surface you created earlier. I then trimmed > extruded > exported to *.stp and iserted into an earlier version of my 123D file (pre-paw) Everything worked great up to this point. I then constrained (tangent assembly constraint) the paw to the spot it was located (worked great, bing-bang-boom). If it's any consolation, 123D would not boolean them together either. I thought it was a shortcoming of 123D so I exported (both bodies as constrained) to *.stp and opened in MoI. Here we sit.

;-\

I guess I should start over with tracing the pdf with some new curves...

At least the body imported correctly this time... ;-)

But next time around for something similar probably try to make the pieces push through each other a little bit instead of having them kind of skimming right along each other. Either that or try to get the exact same surface in the areas that are coincident instead of having one rotated or fragmented differently than the other.

Having them push through a bit tends to be easiest, since it then doesn't make too much difference exactly how the bottom pieces are structured since they will get sliced off anyway.

- Michael

Hi Nick, well I was actually able to get the pieces unioned together in MoI (using Trim + Join method described above), so if you're just looking for a solid result of what you had that's attached above.

But yeah it's good to be kind of wary of PDF data - often times PDF files are really set up just for printing and not really as a source of 3D geometric calculations in mind.

There are quite a lot of things that can be ok for printing but bad for 3D modeling.

Also if the PDF file was generated from one of those PDF printer drivers, those tend to fragment things that were originally curves into a bunch of lines, since that is pretty common for an application to only actually send lines to a printer. So that's why you may rather often see PDFs that have have only polylines with a dense number of line segments in them rather than actual smooth curves...

- Michael

Heh... I found out 123D will and does boolean them. I was selecting the parent of the paw instead of the individual blocks in the browser... Apparently it's something they are fixing. Anyway, if I select each solid piece of the paw it booleans fine. The problem however still lies with exporting to *.stp where virtually every program broke it back into individual blocks that need to be booleaned again... I've learned my lesson with pdfs.