MeshRenderer has wrong bounds when rotated - unity3d

Question

When I try to get the bounds of my models (created in Blender) and show them in Inspector:
As you can see the bounds are correct when the objects are not rotated. But when they are (left-most object) bounds start getting totally wrong.
Here is a script that shows / gets the bounds:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class GetBounds : MonoBehaviour
{
public MeshRenderer mesh_renderer = null;
public bool show_bounds = false;
private void OnDrawGizmos()
{
if (!show_bounds) return;
Gizmos.DrawWireCube(mesh_renderer.bounds.center, mesh_renderer.bounds.size);
Gizmos.DrawWireSphere(mesh_renderer.bounds.center, 0.3f);
}
}
How can I fix this?

Answer 1

In this thread I have come across this image which explains it pretty much
Unity dos not recalculate the Mesh.bounds all the time except when you add a mesh for the first time or "manually" invoke Mesh.RecalculateBounds.
It then uses this local space Mesh.bounds in order to calculate the translated, scaled and rotated Renderer.bounds in global space based on the Mesh.bounds. This way it always has to iterate a fixed amount of 8 vertices of the bounding box.
There was also a solution provided if you want to get the exact bounds calculated directly from the vertices. I adopted and cleaned it up a bit
public class GetBounds : MonoBehaviour
{
public MeshRenderer mesh_renderer;
public bool show_bounds;
public MeshFilter meshFilter;
public Mesh mesh;
private void OnDrawGizmos()
{
if (!mesh_renderer) return;
if (!show_bounds) return;
if (!meshFilter) meshFilter = mesh_renderer.GetComponent<MeshFilter>();
if (!meshFilter) return;
if (!mesh) mesh = meshFilter.mesh;
if (!mesh) return;
var vertices = mesh.vertices;
if (vertices.Length <= 0) return;
// TransformPoint converts the local mesh vertice dependent on the transform
// position, scale and orientation into a global position
var min = transform.TransformPoint(vertices[0]);
var max = min;
// Iterate through all vertices
// except first one
for (var i = 1; i < vertices.Length; i++)
{
var V = transform.TransformPoint(vertices[i]);
// Go through X,Y and Z of the Vector3
for (var n = 0; n < 3; n++)
{
max = Vector3.Max(V, max);
min = Vector3.Min(V, min);
}
}
var bounds = new Bounds();
bounds.SetMinMax(min, max);
// ust to compare it to the original bounds
Gizmos.DrawWireCube(mesh_renderer.bounds.center, mesh_renderer.bounds.size);
Gizmos.DrawWireSphere(mesh_renderer.bounds.center, 0.3f);
Gizmos.color = Color.green;
Gizmos.DrawWireCube(bounds.center, bounds.size);
Gizmos.DrawWireSphere(bounds.center, 0.3f);
}
}
Result:
In WHITE: The MeshRenderer.bounds
In GREEN: The "correct" calculated vertex bounds