Unity3d. Convex collider restrictions

Question

I want to predicate that I cannot set collider to convex.

I already found some restrictions: - trigs must be between 3 and 254.

But there still some cases that I can not handle:

Vector3[] vertices = new Vector3[] {
new Vector3(-0.1f, -100f, 0f),
new Vector3( 0.1f, -100f, 0f),
new Vector3(  0f,  100f, 0f),
new Vector3(  0f,  0f, 0.1f),
};

int[] tris = new int[] {
0, 1, 2,
0, 1, 3,
1, 2, 3,
2, 0, 3,
};

returns:

Unhandled log message: [Error] [Physics.PhysX] ConvexHullBuilder::CreateTrianglesFromPolygons: convex hull has a polygon with less than 3 vertices! UnityEngine.MeshCollider:set_convex(Boolean) BzKovSoft.ObjectSlicer.ObjectSlicer.MyTests:Test() (at Assets/BzKovSoft/ObjectSlicer/Editor/MyTests.cs:43) System.Reflection.MethodBase:Invoke(Object, Object[]) NUnit.Framework.Internal.<>c__DisplayClass9_0:b__0() UnityEditor.EditorApplication:Internal_CallUpdateFunctions()

Could you advice maybe a reference to all this rules for convex collider?