Selective Highlighting of Vertices in Unity3D meshes

TLDR; I created a behaviour script that lets you highlight vertices on any type of mesh in unity3d.

I have been playing lately with mesh deformations and I needed a way to visually see the selected vertices (and neighbor vertex connections) for the meshes I was manipulating. To do this I created a simple MonoBehaviour script that one attaches to an empty game object that is a children of the mesh that is being manipulated and simply call two functions to highlight or remove vertices of said mesh.

Someone might find this utility useful. There might be other ways to do it but this one that I developed works pretty well for my needs. If you find it useful let me know; it makes me happy to know that I helped someone on the interwebs with my work :).

Its worth mentioning that the mesh to manipulate *needs* to have a mesh collider. This is how it looks:

Anyways. Without further ado. Here it goes:

And a simple script that makes it work by “Painting” with the left click on certain parts of the mesh.

To make it work, simply create an empty Game Object as a children of the mesh to highlight and attach the “NeighborVertexHighlighter” script component to it. To test the script you can attach the “PaintRemoveVerticesExample” script to the mesh to highlight. *Its important to remember that the mesh to be highlighted requires a MeshCollider component*

How it works:

The way this works is by creating a list of arrays of integers for each of the vertices; this list contains the indices of the neighbor vertices for any given vertex. This neighbor list is calculated on a separate thread (to not block the main thread) and is Order the number of triangles the mesh has.

Two main functions can be called in the highlighter script. AddIndex(int i) and RemoveIndex(int i), One just needs to pass the index of the vertex one wants to highlight and the script will automatically create a mesh with the indices that are going to be highlighted.

Internally a dictionary<Vector3, VertexNeighbor> contains the current indices that are being highlighted. This dictionarly is modified with AddIndex and RemoveIndex functions. It is worth noting that I used the position of the vertex as the key instead of the index of the vertex in the vertex array because I found that some meshes (like the base cube in Unity) contain different separate vertices in the same exact position, hence this algorithm would highlight only the index neighbors. Because of this is useful to use the position of the vertex as the key in case the mesh contains different vertices in the same position.

In order to map/know which vertex refers to the original mesh in the highlighted mesh, another dictionary is used, its called indexRemap<int, int>. This dictionary easily lets one translate from the mesh to highlight vertex indices to the highlighted mesh vertex indices.

Finally, after an index is added or removed, a line mesh is created with the already saved indices in the class. The idea is pretty simple but works pretty well.

Future work:

Perhaps this could be further optimized by not creating a mesh every time an index is added or removed but perhaps having all the indices of the original mesh and adding, removing triangles. But unfortunately this will make it consume more memory. So I will have to assess how good this will work in huge meshes.