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When I move some vertices around randomly, I end up with this:

alt text

void Start() {
    Mesh mesh = GetComponent<MeshFilter>().mesh;
    Vector3[] vertices = mesh.vertices;
    Vector3[] normals = mesh.normals;

    for(int i = 0; i < vertices.Length; i++) {
       float rand = Random.Range(-0.1f, 0.1f);
       vertices[i].x += rand;
       vertices[i].y += rand;
       vertices[i].z += rand;
    }

    mesh.vertices = vertices;
    mesh.RecalculateNormals();
}

Am I missing something?

Answer 1

If you print vertices.Length, you'll see it's 24 -- 4 for each face. The code is working perfectly. Each of the three verts at a corner is getting its own random shift.

Turns out graphics cards want to smooth-shade everything. When you make a hard-edge (a crease, in a modelling program) you're really splitting the verts on that edge. Seems a waste of verts, but every other way takes longer to draw. Technically, it's possible to set a model to no smooth-shading at all, but you have to specially redo the normals based on the order of the face array, which is too big a pain.

There's no easy pattern to find "same" verts: Debug.Log shows (0.5,0.5,0.5) occurs at indexes 2, 8 and 21, for example. I guess each time you change one, you could loop again to also change ones with the same values by that amount; with another array of bools to marked them as changed.

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What's wrong with this simple mesh manipulation?

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