CompuServe Messages

Here are the 2 best messages we have a booleans from the Boolean-Master <g>: Hi Michele, Boolean King? I hardly think so! However, since I do a lot of the mechanical things you refer to, I've done a big pile of booleans and have had to figure things out. 1> zits around holes… Almost always when I see the pinched look or smoothing prolems it has been due to tiny faces or slivers the boolean has added. These are often invisible until zoomed way in. The problem is the attempt to smooth over an edge at a face or two where there should be no smoothing. AutoSmooth doesn't help – my guess (I have not done the math) is that when working on a very small scale, the trig calculations to determine the angle between faces suffers from a lack of precision. This also is a problem with very thin slivers of faces. To fix, I do one or more of three things: a) Zoom way in, look for tiny faces, and manually weld vertices to collapse the bad faces. b) Use the ol' select & weld strategy to collapse the tiny faces. I set the weld threshold to something smaller than the smallest edge I want to maintain, select all the vertices in the object, execute Modify/Vertex/Weld "Selected", then re-AutoSmooth. This can backfire, so hold first. c) Manually smooth, or rather unsmooth: select all the faces on the flat plane and remove the smoothing. 2>incomplete boolean, adjust… My humble obversations note that this is very often caused by topology – asking the algorithm to figure out which surface is out. Several causes and fixes: a) Bad geometry, with missing faces or internal faces – fix the geometry such that it has a single, unbroken surface, then unify normals. b) good geometry but inconsistent normals – unify normals. c) overlapping elements. This is probably the most common cause of "cannot complete boolean operation". If an object is made up of several elements, a boolean will often fail if it overlaps more than one element, *especially* if the elements themselves within one object are overlapping. In this case, a boolean, for example a subtraction, can usually be completed with 1) detach the elements into separate objects, 2) union these back into a single object, then 3) perform the boolean subtraction. Note that depending on the object, a "select & weld" step may be necessary after each union in step 2. Experiment with this technique using at least three overlapping spheres. A variation of this is the case of a subtraction thru the folds of convoluted object, even if the convoluted object has consistent topology. I've had cases where this confused the boolean algorithms and fixed it by making some intermediate objects and doing the boolean in stages. Well, after I typed this I found a copy of a previous message from the past which contained additional ramblings. I'm resending it to you (without reading it to correct any embarrassing goofs <g>) in case you are interested. Some of it looks like duplication, but I don't have time to sort it out just now. Well, have fun on your trip! JKJ (full of bool, once again) [old message to follow] [More]