Find 1-ring adjacent vertices of a vertex on mesh

openNURBS
1

Hi,
I am using ON_MeshTopology to access ON_Mesh data, but still not familiar with it. I want to find a ON_MeshTopologyVertices adjacencies as picture below, can anyone told me how to do it?
image

2

For a mesh topological vertex (ON_MeshTopologyVertex), you can get a list of edges that start or end by looking at its m_topei array that has length m_topei_count. These numbers are indices in the topology’s m_tope array, giving a list of topological edges. Each edge has two topological vertices, in its m_topv array. One will be the index of the vertex you started at, the other the index of the vertex in the 1-ring.
If you want to have it sorted, call SortVertexEdges first.

https://mcneel.github.io/rhino-cpp-api-docs/api/cpp/class_o_n___mesh_topology.html#aeca0c893d61e4163c80301cdd3a408f9

3

There’s also

https://developer.rhino3d.com/api/rhinocommon/rhino.geometry.collections.meshtopologyvertexlist/connectedtopologyvertices

4

Thank you for your reply,
Is that means that I still need to determine which one is the adjacenct vertex after I obtaining ON_MeshTopologyEdge.m_topvi[2] from an ON_MeshTopologyVertex,?

Here is my code implementation

const ON_MeshTopologyVertex& mesh_top_vertex = mesh_top.m_topv[index];

// traverse all TopologyEdge
for (int i = 0; i < mesh_top_vertex.m_tope_count; ++i) {
	const ON_MeshTopologyEdge& mesh_top_edge = mesh_top.m_tope[i];

	// determine which one is adjacent vertex
	int adjVertexIndex;
	if (mesh_top_edge.m_topvi[0] == index) {
		adjVertexIndex = mesh_top_edge.m_topvi[1];
	}
	else {
		adjVertexIndex = mesh_top_edge.m_topvi[0];
	}
    
    // do sth to adjVertexIndex
}
5

Found that the previously submitted code had many errors…
the modified version are as follows:

// Get TopologyVertex
const ON_MeshTopologyVertex& mesh_top_vertex = mesh_top.m_topv[index];

for (int i = 0; i < mesh_top_vertex.m_tope_count; ++i) {

	// traverse all TopologyEdge
	int topeIndex = mesh_top_vertex.m_topei[i];
	const ON_MeshTopologyEdge& mesh_top_edge = mesh_top.m_tope[topeIndex];

	// determine which one is adjacent vertex
	int adjVertexIndex;
	if (mesh_top_edge.m_topvi[0] == index) {
		adjVertexIndex = mesh_top_edge.m_topvi[1];
	}
	else {
		adjVertexIndex = mesh_top_edge.m_topvi[0];
	}
6

looks good to me