Wrong BoundingBox in BrepFace

Rhino Developer
,
1

Hi, I am struggling with getting the correct BoundingBox in C++ of the spherical cap surface of the file in attach.
I wrote this code to evaluate the bounding box.

const CRhinoObject* p_object = RhinoApp().ActiveDoc()->LookupObject(srfId);
				
if (p_object != nullptr)
{
	CRhinoObjRef ref(p_object);
	const ON_Brep* p_brep = ref.Brep();
	if (p_brep != nullptr)
	{			
		ON_BoundingBox bb0 = p_brep->BoundingBox();
					
	    for (int i = 0; i < p_brep->m_F.Count(); i++)
	    {
			const ON_BrepFace* p_face = p_brep->Face(i);
			if (p_face != nullptr)
			{
				ON_BoundingBox face_bound;						
				p_face->GetTightBoundingBox(face_bound);
				ON_BoundingBox bb1 = p_face->BoundingBox();
			}
		}
	}
}

I noticed that bb0, bb1 and also face_bound return a wrong maximum Z bb value of 3.91 mm while I expected to have 0.0. The other bounding box values are correct.
I tried also to untrim the surface but I stil have the same results.
wrong_sphere_bb.3dm (7.4 MB)

2

Hi @Gabriele_Cuccolini,

In this case, were you have a document object, you might just call RhinoGetTightBoundingBox.

cmdSampleBoundingBox.cpp

– Dale

3

Hi Dale, thank you very much. I changed my code with this:

		for (int k = 0; k < drive_geometries.Count(); k++)
			{
				const CRhinoObject* p_object = RhinoApp().ActiveDoc()->LookupObject(drive_geometries[k]);

				if (p_object != nullptr)
				{
					ON_SimpleArray<const CRhinoObject*> objArray;

					objArray.Append(p_object);

					ON_BoundingBox bb;
			
					RhinoGetTightBoundingBox(objArray, bb);

					drive_surfaces_bound.Union(bb);
				}
			}

And now I have the correct bounding box.
So in your opinion is always better to use this method to compute the bounding box of a collection of surfaces?
bye
gabriele