he size calculated by Bnd_box is diffreren from actual size

Luke jk's picture
Luke jk
Wed, 05/10/2023 - 14:04
Forums: 
Modeling Data and Algorithms

Hi,I get a ellipse.The actual elliptical short half axis is 20, but The size calculated by Bnd_box is 21.75!
Thanks for everyone's reply!

Attachments: 
Binary Data section.brep
gkv311 n's picture
gkv311 n
Wed, 05/10/2023 - 15:20
  1. Bnd_Box is just a numbers' placeholder, it cannot calculate anything from an ellipse.
  2. BRepBndLib::Add(), if you're using this particular algorithm, calculates an approximated AABB that fully encloses the given geometry and topology (e.g covers also encoded tolerances), but could be also larger of original shape. This is expected behavior of this algorithm.
Luke jk's picture
Luke jk
Thu, 05/11/2023 - 04:22

I will experiment with your suggestion! you help me better understand bnd_ box.

Mikhail Sazonov's picture
Mikhail Sazonov
Wed, 05/10/2023 - 22:34

To get the tight bounding box use the method AddOptimal instead of Add.

Luke jk's picture
Luke jk
Thu, 05/11/2023 - 04:17

Thanks for your reply! Mikhail! it work well!