2. Fundamentals

Reading Render Meshes

by Dale Lear

This brief guide describes how to read render meshes using the openNURBS toolkit.

If you are developing software to read .3dm files, you might find that the software only seems to read NURBS data; but render meshes are ignored. We do provide methods for third-party developers to read render meshes from .3dm files.

An object’s render meshes are stored on that object. For example, the render meshes for an ON_Brep object are stored on that brep. The developer can obtain an object’s render meshes from a brep by calling ON_Brep:GetMesh.

It should be noted that if the call to ON_Brep:GetMesh does not return any meshes, then the object did not have any render meshes.

If you are referencing the Example_read sample included with the openNURBS toolkit, then after the 3DM file has been read, you can obtain the render meshes from the ONX_Model object as follows:

ONX_Model model = .....

int i;
for( i = 0; i < m_object_table.Count(); i++ )
{
 ONX_Model_Object model_object = m_object_table[i];
 ON_Brep* brep = ON_Brep::Cast( model_object->m_object );
 if( brep )
 {
   ON_SimpleArray<const ON_Mesh*> meshes;
   int mesh_count = brep->GetMesh( ON::render_mesh, meshes );
   if( mesh_count )
   {
      // TODO: do something with the array of meshes..
   }
 }
}