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tagosaku

apply boolean twice problem

hi, when I try to use a boolean node twice, second boolean result is always broken because I guess a connectivity issue. Houdini  cannot understand the connectivity from first boolean result.
 
I know some people says to cut together with many cutters, but I have a certain situation to cut separately. For instance first boolean produces 500 pieces, and keep 300 pieces and use second booleans for other 200 pieces, and so on.
 
Some artist do after-1st-boolean > loop start > delete all pieces(groups) except one favorite piece > do-2nd-boolean > loopEnd > merge together.
Or, I do translate and separate each other of pieces in order to make spaces between each pieces, then apply 2nd boolean, and it works
 
I wonder if anyone knows smarter methods, instead of translating or looping

booleanTwice.hipnc

booleanA.JPG

booleanB.JPG

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I tested with one Boolean using 2 cutters in one go...it works...but since you said you sometimes have no choice but to do multi Booleans...I guess the problem is everytime you shatter...it creates a lot of coincident faces (where the cuts are)...then in your subsequent Boolean(s)...if you say Resolve Self Intersections...this is where trouble starts because of those coincident faces....untick the Resolve Self Intersections and you won't get those nasty explosions...

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For multi Booleans route:

OK, so we know the coincident faces cause problems...well....get rid of them...how ? Cheat !!!

So your cutter sheets are infinitely thin...causing problems..my cheat is to extrude it a tiny bit..by 0.001 and make sure to Output Back !!! Then in the Boolean, instead of shatter, use Subtract and also the surfaces are now Solid...so now there is a tiny gap between the cuts....hey hey...no coincident faces !!! So even with Resolve Self Intersection ON...it doesn't 'shat' itself to pieces....

(reminder: if you were doing a single Boolean, then there's no need to extrude the cutter(s)...)

booleanTwice2.hipnc

Edited by Noobini

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it sounds boolean node is really designed to use once. Thanks for your tip. I will check it out!

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