polyexpand2D + boolean = bad result!

Forums Houdini Indie and Apprentice polyexpand2D + boolean = bad result!

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olivierth: Member; 1004 posts; Joined: April 2017; Offline

Feb. 4, 2019 8:12 a.m.

Hi!

I was using a boolean to cut the shape of the floor through the wood planks. Both geos are 2D and the boolean was working. When I decided to “shrink” the shape of the walls by adding a polyexpand2D sop right before the boolean, it stopped working. The result of the boolean is zero points.

I uploaded a simpler version of a circle through a grid. The same problem happens

Edited by olivierth - Feb. 4, 2019 08:13:28

Attachments:
polyexpand2d_boolean_problem.hip (66.3 KB)
polyexpand2d_boolean_b.JPG (59.8 KB)


robsdesign: Member; 236 posts; Joined: March 2015; Offline

Feb. 4, 2019 12:31 p.m.

I'm not sure why it happens but if you compare the Y size of the circle, transform and polyexpand you'll see it's off zero on all except the circle. You can add a transform sop after the polyexpand and scale Y to 0 or use a match size sop but neither return it to zero. (But close enough that the Boolean works again)


olivierth: Member; 1004 posts; Joined: April 2017; Offline

Feb. 4, 2019 2:40 p.m.

AH!!

I'll just use a wrangle set the Y to exactly what it needs to be.

Thanks a lot!

-Olivier


vusta: Member; 555 posts; Joined: Feb. 2017; Offline

Feb. 7, 2019 4:44 p.m.

this alternate version just works.

Attachments:
vu_polyextrude.hiplc (72.8 KB)


olivierth: Member; 1004 posts; Joined: April 2017; Offline

Feb. 8, 2019 8:03 a.m.

Ah! I always forget about using the inset feature!

Thanks.

-Olivier


voidcoder: Member; 12 posts; Joined: May 2023; Offline

June 25, 2023 5:26 p.m.

Banging head against the wall for several hours now. Same issue. PolyExpand2d produced geometry will always mess boolean ops.

I have a curve which I first need to expand then crop using another randomly shaped 2D mesh as a mask. If I use PolyExtrude on the curve the produced mesh will work fine with any boolean ops. However if I use PolyExpand2d the boolean becomes broken. Trouble is PolyExtrude doesn't quite work for what I need this for, need PolyExpand2d for uniform expansion on both sides of the curve.

Any ideas what is going on please?

Attachments:
Screenshot 2023-06-25 at 22.23.42.png (345.9 KB)
CurveIntersectTest.hipnc (183.2 KB)


CYTE: Member; 675 posts; Joined: Feb. 2017; Online

June 26, 2023 10:42 a.m.

It's because polyexpand isn't absolutely flat.
Just add a transform after polyexpand and scale Y axis to zero.

Cheers
CYTE


voidcoder: Member; 12 posts; Joined: May 2023; Offline

June 28, 2023 4:29 a.m.

Worked. Thank you CYTE!

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