private var numQuads = 10000;
private var verts = new Vector3[numQuads * 4];
private var uv = new Vector2[numQuads * 4];
private var tris = new int[numQuads * 6];
Debug.Log(verts.Length);
Debug.Log(uv.Length);
Debug.Log(tris.Length);

function Start () {
for (var n=0; n< numQuads; ++n)
{
    tris[n*6 + 0] = n*4 + 0;
    tris[n*6 + 1] = n*4 + 1;
    tris[n*6 + 2] = n*4 + 2;
    tris[n*6 + 3] = n*4 + 0;
    tris[n*6 + 4] = n*4 + 2;
    tris[n*6 + 5] = n*4 + 3;

    uv[n*4 + 0] = Vector2(0,0);
    uv[n*4 + 1] = Vector2(0,1);
    uv[n*4 + 2] = Vector2(1,1);
    uv[n*4 + 3] = Vector2(1,0);

}
var mesh = new Mesh();
mesh.vertices = verts;
mesh.uv = uv;
mesh.triangles = tris;
}