I am trying to combine many objects (in the order of hundreds) in BLENDER by the UNION operation (boolean modifyer, union). Correspondingly I wrote a small script that cycles through the objects, combining one after the other with the alwyays growing first object. This script works quite well for a few objects and operations (that I can also verify by hand). If their number rises, however, I get funny results. Usually several objects are missing from the growing "all-union-object". I assume that the UNION-function at some place messes up (as described in the www), and that all subsequent UNION-operations suffer from this. Is there any Modifier (or other way) that I could treat the single objects with in order that this UNION works? I have tested so far the REMESH and TRIANGULATE modifiers and also have scaled the single objects by different numbers in order to get rid of identical faces that might exist among the objects. Unfortunately, all this seems to change only the ultimate output and the appearance after combining a few objects. Cycling through the larger list of objects, however, always gives problems. Any help is highly appreciated.

To the background: From another program I get initially in VRML/WRL many different spheres and cylinders that in part are identical and in part overlap. I cannot change this behavior and would like to have in the end one single entity (or object) like the UNION of all those little objects or the outer surface encompassing all those little objects. Importing to BLENDER (which works as expected) and combining all little objects by UNION (my question) would solve the problem (at least in theory if there were not the problem I am asking here ...). I am certainly not limited to this approach, so maybe there is also another one that would circumvent this issue with the multiple UNION in BLENDER ...

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    $\begingroup$ Providing the script would make it far easier to see what is going on. $\endgroup$ – batFINGER Sep 20 '17 at 17:03
  • $\begingroup$ Dear batFINGER: I don't think that the script by itself is the problem. The issue is rather that it works only for a few objects (and hence I feel quite comfortable with the script itself). That's also why I think that I have to add something to get the multiple UNION to work. I am happy to share the script (if this is of help) but, unfortuantely, do not know how. This "comments section" is probably not the right place but the only button I could click on at this stage. Where I should put it? $\endgroup$ – Manny Sep 21 '17 at 10:55
  • $\begingroup$ If its of moderate length post it here. Simply indent over 1 extra, (in blender text editor select all, tab, copy and paste here) if its large use pasteall.org/code $\endgroup$ – batFINGER Sep 21 '17 at 11:03
  • $\begingroup$ Dear batFINGER, I have pasted the code at: pasteall.org/570976. Most of it is not really interesting and in part also derives from earlier versions of the script such that not all If's etc. are still relevant. I hope it shows where I am heading for ... $\endgroup$ – Manny Sep 21 '17 at 14:31
  1. Join all the objects you want to unite using Ctrl+J
  2. Create a new cube that contains all the joined objects inside
  3. Use the Boolean Modifier on the Cube with Carve Solver and Intersect Operation

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  • $\begingroup$ At first glance I though great, easy and many thanks, but upon closer inspection things don't work for me completely. The objects seem to be linked together but not combined by a complete UNION operation. Internal parts of the meshes or even complete internal objects (like a smaller sphere inside a larger sphere) are still present. As they create problems later on, I wanted to get rid of them by the attempted multiple UNION. Also I do not have the "Overlap Threshold" in my Interface - is this possibly due to different versions or should I set something else. I am using BLENDER v2.78. $\endgroup$ – Manny Sep 21 '17 at 10:34
  • $\begingroup$ I used blender 2.78c. The problem with internal objects is not solved by this approach, I admit. What happens if you use this process, and after you get the resulting mesh, use another boolean with another cube? Are the internal objects still present? Please try the bmesh solver too. Other than that I have no idea for now, sorry. $\endgroup$ – Dimali Sep 21 '17 at 13:21

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