[C++] ON_PlanarSections - how does this work!?

Rhino Developer
1

Hi,

I was trying to get ON_PlanarSections::AttachToObject running, but so far I have not been able to see a result. Also, I don’t know exactly what to expect as a result so that doesn’t really help.

So far, this is what I have. After AttachToObject, which is successful, what is supposed to happen? Should I be able to see something in the document? Can I query the planarsections object somehow? When the object updates, are the planar sections automatically updated too?

Any hints on how to proceed are much appreciated!

CRhinoObjRef objRef; // obtained by selecting one surface_object
const CRhinoObject* obj = objRef.Object();
if (!obj) 
{
    // when nothing was selected there isn't anything left to do.
    return nothing;
}
obj->Select(false);

const ON_Surface* srf = objRef.Surface();
if (!srf)
    return nothing;

ON_SimpleArray<const ON_Mesh*> arr;
obj->GetMeshes(ON::mesh_type::any_mesh, arr);
    
if (arr.Count() == 0)
{
    ON_MeshParameters mp;
    mp.DefaultAnalysisMeshParameters();
    ON_Mesh* m = srf->CreateMesh(mp);
    arr.Append(m);
}
    
ON_Plane xp(ON_3dPoint(0,0,0), ON_3dVector(1,0,0));
ON_MeshXPlane mxp( *(arr[0]), 0);
ON_SectionAnalysisPlane p;
p.m_plane_equation = xp.plane_equation;
if (!ON_PlanarSections::AttachToObject(obj, mxp, srf, ON_SectionAnalysisAppearance::Default, p))
    RhinoApp().Print("Failed to attach planar sections to object\n");
    
context.m_doc.Redraw();
return success;
2

The openNURBS definitions is available. But thats it. You’ll need some Rhino stuff exposed to use this.

Just curious, what are you looking to do?

3

I’m trying to show planar sections in all world-axis directions on ship hull shapes that update their shape while the user is dragging control points.

Since my original post, I have since explored further and now have a working solution based on ON_PlanarSections that still needs some further optimization. I will try to post an example on its use later.