Get Normal of a mesh when point.m_ci.m_type == ON_COMPONENT_INDEX::meshtop_vertex (c++)

Rhino Developer
1

Hi;
what is wrong with my code, Why is the point has transform going in the wrong direction ?
This is my file LVI192067P.3dm (396.0 KB)

p
p911×686 74 KB 

CRhinoGetObject go;
go.SetCommandPrompt(L"SELECT POINT");
go.SetGeometryFilter(CRhinoGetObject::point_object);
go.GetObjects(1, 1);
if (go.CommandResult() != CRhinoCommand::success)
	return go.CommandResult();
CRhinoGetObject go1;
go1.SetCommandPrompt(L"SELECT MESH");
go1.SetGeometryFilter(CRhinoGetObject::mesh_object);
go1.GetObjects(1, 1);
if (go1.CommandResult() != CRhinoCommand::success)
{
	return go1.CommandResult();
}
ON_MESH_POINT point;
ON_3dVector nor = ON_UNSET_POINT;
ON_Mesh* mesh = const_cast<ON_Mesh*>(go1.Object(0).Mesh());
if (!mesh->HasFaceNormals())
	mesh->ComputeFaceNormals();
mesh->GetClosestPoint(go.Object(0).m_point, &point);
if (point.m_ci.m_type == ON_COMPONENT_INDEX::meshtop_vertex)
{
	ON_SimpleArray<int> faces;
	const ON_MeshTopology& top = mesh->Topology();
	int topvi = top.m_topv_map[point.m_ci.m_index];
	const ON_MeshTopologyVertex& topvert = top.m_topv[topvi];
	for (int i = 0; i < topvert.m_tope_count; i++)
	{
		const ON_MeshTopologyEdge& topedge = top.m_tope[topvert.m_topei[i]];
		for (int j = 0; j < topedge.m_topf_count; j++)
			faces.Append(topedge.m_topfi[j]);
	}
	faces.QuickSort(&ON_CompareIncreasing<int>);
	int fi = -1;
	for (int i = faces.Count() - 1; i >= 0; i--)
	{
		if (faces[i] == fi)
			faces.Remove(i);
		else
			fi = faces[i];
	}
	ON_3dVector ve_s = mesh->m_FN[faces[0]];
	for (int i = 1; i < faces.Count(); i++)
	{
		ON_3dVector ve_e = mesh->m_FN[faces[i]];
		ve_s = ve_s + ve_e;
	}
	ve_s.Unitize();
	ON_3dPoint point_tranform(point.m_P);
	point_tranform.Transform(ON_Xform::TranslationTransformation(ve_s));
	RhinoApp().ActiveDoc()->AddPointObject(point_tranform);
}
RhinoApp().ActiveView()->Redraw();
return success;
2

Hi @suc_kiet,

What is the code supposed to do? Any details you can provide might be helpful.

– Dale

3

HI@ dale,
I just want to add up all the vector of the faces which share the vertex, but it seam have some thing wrong in my code that return the wrong result to me, Am I getting the faces the wrong way or getting the vertex the wrong way?

4

Hi @suc_kiet,

Why don’t you just use the vertex normal, which is an average of the face normals?

– Dale

5 
ON_3dVector ve_s = mesh->m_FN[faces[0]];
for (int i = 1; i < faces.Count(); i++)
{
	ON_3dVector ve_e = mesh->m_FN[faces[i]];
	ve_s = ve_s + ve_e;
}

I think I have get it by this way, but it seam wrong

6

HI@Dale,
In my opinion, if my code is run good, the return point should be in the direction of this red line instead of being in the purple spot

E_T5K@Z4CXD)44`YANRLJD
E_T5K@Z4CXD)44`YANRLJD692×686 46.1 KB
.

7

Hi @suc_kiet,

My example isn’t much different than yours - see if it helps any.

cmdTestSuckiet.cpp (3.7 KB)

– Dale

8

Hi @dale,
Thank you for your help.
What is difference between int topvi = top.m_topv_map[point.m_ci.m_index] and const ON_MeshTopologyVertex& topv = meshtop.m_topv[mesh_point.m_ci.m_index] ?