Invalid ON_Brep from OpenNURBS

openNURBS
1

Hi.
When exporting geometries with OpenNURBS 8.0, I found some ON_Brep with invalid bounding box and the meshes got from ON_Brep::GetMesh() seem distorted. For example, ON_Brep::m_box：{m_min={x=-1.033144777886e-309#DEN y=0.0000000000000000 z=18373.311983570755 } m_max={x=4252825.4858648088 y=3476811.6673364569 z=4.9228653096998468e+179 } }. How can I solve these problems? Thanks.

2

It would be helpful if you tell some more about how you got the invalid ON_Brep objects, and share your code that gives this problems if possible.

3

This is part of my code.

ONX_ModelComponentIterator it(onxModel, ON_ModelComponent::Type::ModelGeometry);
for (ON_ModelComponentReference mcr = it.FirstComponentReference(); false == mcr.IsEmpty(); mcr = it.NextComponentReference())
{
    const ON_ModelComponent* modelComponent = mcr.ModelComponent();
    const ON_ModelGeometryComponent* mgc = dynamic_cast<const ON_ModelGeometryComponent*>(modelComponent);
    const ON_Geometry* geometry = mgc->Geometry();
    ON_Brep* aBrep = const_cast<ON_Brep*>(dynamic_cast<const ON_Brep*>(geometry));
    //get boundingBox
    if (NULL != aBrep)
    {
        ON_SimpleArray<const ON_Mesh*> meshs;
        int retValue = aBrep->GetMesh(ON::MeshType(4), meshs);
        for (int mesh_index = 0; mesh_index < meshs.Count(); mesh_index++)
        {
            const ON_Mesh** aMesh = meshs.At(mesh_index);
            int size = (*aMesh)->m_dV.Count() ? (*aMesh)->m_dV.Count() : (*aMesh)->m_V.Count();
            for (int vertexIndex = 0; vertexIndex < size; vertexIndex++)
            {
                ON_3dPoint point = (*aMesh)->m_dV.Count() ? (*aMesh)->m_dV[vertexIndex] : (*aMesh)->m_V[vertexIndex];
                //get vertices...
            }
        }
    }
}
4

Hi @sw11,

Can you share the .3dm file that produces this?

Thanks,

– Dale

5

Hi Dale,
The .3dm file is too large(997M), how can I send it to you?

6

https://www.rhino3d.com/upload

Sent to dale@mcneel.com

7

The file has been uploaded.

8

Hi @sw11,

I am not seeing your file. Can you zip and resend?

Thanks,

– Dale

9

Hi @dale
I’ve reuploaded it. Did you received the file?

10

Hi @sw11,

Yes, I was finally able to get your file - thank you.

I’m not finding any Breps with invalid bounding boxes.

  int brep_count = 0;
  int invalid_bbox_count = 0;

  ONX_ModelComponentIterator it(model, ON_ModelComponent::Type::ModelGeometry);
  const ON_ModelComponent* model_component = nullptr;
  for (model_component = it.FirstComponent(); nullptr != model_component; model_component = it.NextComponent())
  {
    const ON_ModelGeometryComponent* model_geometry = ON_ModelGeometryComponent::Cast(model_component);
    if (nullptr != model_geometry)
    {
      const ON_Brep* brep = ON_Brep::Cast(model_geometry->Geometry(nullptr));
      if (nullptr != brep)
      {
        brep_count++;
        ON_BoundingBox bbox = brep->BoundingBox();
        if (!bbox.IsValid())
        {
          invalid_bbox_count++;
        }
      }
    }
  }

8432 Breps, 0 with invalid bounding boxes.

To compute the bounding box of a mesh, use ON_Mesh::GetBoundingBox.

– Dale

11

Hi @dale ,
For example, ON_ModelGeometryComponent{af5e78fb-be34-48bf-834b-ae1a4c4e85eb} and
{9170d6f7-1390-4df7-bfb6-8cc77b3f3200}, the z value of their box.m_max is extremely large. Is that normal?
I also get the corresponding meshes from ON_Brep::GetMesh(). And the bounding box computed from ON_Mesh::m_dV is different from ON_Mesh::BoundingBox(). And the mesh got from brep seems to be distorted when rendering. Why does this happen?
Thanks.

12

Hi @sw11,

The two objects appear to be microscopic - use Rhino’s SelId command to select them.

The model’s unit seem is in millimeters, seems wrong.

– Dale

13

Hi @dale ,
When I use the SelId command, I still can’ see the two objects. May be the .3dm file obtained from the upstream users is wrong. - so Is the problematic bounding box caused by microscopic objects? Is there any approach to identify this kind of objects in advance?