CGAL users discussion list

[Mael Rouxel-Labbé <>]

Hello,

The geometric traits class is a class that describes the requirements on the geometric objects used in an algorithm, here the oriented bounding box computation algorithm. These requirements are described by a concept (https://doc.cgal.org/latest/Optimal_bounding_box/classOrientedBoundingBoxTraits__3.html). If you do not implement yourself a class meeting these requirements - which is the typical situation -, CGAL uses a class which fits these requirements; here it is CGAL::Oriented_bounding_box_traits_3 (https://doc.cgal.org/latest/Optimal_bounding_box/classCGAL_1_1Oriented__bounding__box__traits__3.html). This class is called a model of the concept.

As the concept (OrientedBoundingBoxTraits_3) describes, matrix manipulations are required in the OBB computation algorithm. The model provided by CGAL (CGAL::Oriented_bounding_box_traits_3) uses Eigen to implement these matrix operations, which thus makes Eigen required except if you create and provide another model class that fits the requirements of the concept with another matrix implementation.

Best,
Mael

On 30/09/2022 16:51, Bob Bill ( via cgal-discuss Mailing List) wrote:

Dear all,

I am trinyg to compile the simplest example from the Optimal Bounding Box page (https://doc.cgal.org/latest/Optimal_bounding_box/Optimal_bounding_box_2obb_example_8cpp-example.html).

and I get the following error, which is expected since I don't have Eigen: 

[build] /usr/include/CGAL/Optimal_bounding_box/oriented_bounding_box.h:348:3: error: static assertion failed: You must provide a traits class or have Eigen enabled!

However, from the message it seems that by providing a Traits class it would be possible to make this work. What does it mean?

Best,

Bob

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