checking self intersecting open brep

Replies to This Discussion

Permalink Reply by Balázs Hegedus on May 16, 2016 at 3:31am

Any idea? Anybody?

Permalink Reply by Daniel González Abalde on May 16, 2016 at 5:00am

I do not know if this will work, but try it.

Attachments:

• SelfIntersectingOpenBrep.gh, 18 KB

Permalink Reply by Balázs Hegedus on May 16, 2016 at 11:17am

Hi Daniel,

Thanks for your solution but it seem to be not working with my flat breps.

I enclose 5 derived breps. The smallest one is self intersecting.

Attachments:

• open breps.3dm, 204 KB

Permalink Reply by Daniel González Abalde on May 16, 2016 at 11:51am

Since brep faces are trimmed, the isotrim not work well. Replace it with Scale with a factor of 0.999 and will work in your case just with the initial method. 

Permalink Reply by Balázs Hegedus on May 24, 2016 at 3:54pm

Hi Daniel,

I have been experimenting with your formula for a while. Actually I have to check 100-200 open flat breps at a time. Unfortunately this solution is quite unreliable.

For example I have 5 open breps and this formula says that all 5 is self intersecting despite if you check the visually, anyone can see that only 2 of 5 is self intersecting.

I tried to upload the files, but I cant do it, because I "500: Unexpected Error", and my message appears without the attached files. 

Is there any formula available which is an exact solution? At least for my flat breps. I have searched on the net for self intersection surfaces problem, but I have found only very very long and complicated mathematical formulas which I could not translate to grasshopper.... 

Permalink Reply by Mohamed Naeim on May 25, 2016 at 12:15am

i think i solved it 

please try this one and let me know if it works 

it depend on simple algorithm i shared two days ago

now it check first whether a face is colliding with other faces

then it tells which faces are colliding stating their indexes after culling self 

finally, then if a face is colliding with more than 2 faces (typical number of colliding edges for your shape)

then the open brep holistically is colliding with itself

Attachments:

• brep collision.gh, 18 KB

Permalink Reply by Mohamed Naeim on May 25, 2016 at 12:41am

only smallest intersecting/tried 

option two, if u build faces chronically, u can check if intersecting faces indexes are predecessor or successor to face index, otherwise it will be just intersected face. 

Permalink Reply by Balázs Hegedus on May 25, 2016 at 3:44pm

Hi Mohamed,

Thank you very much! It seems to be reliable!

Cheers!