UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36

Steps to reproduce the problem:
1. Run the scene here : http://playground.babylonjs.com/#SF5KIL
2. Comment / Uncomment the line about sphere.scaling (line 10)

What is the expected behavior?
You would expect this line not to change anything.
-> The scaling variation is very small and should not be noticeable.

What went wrong?
Vertices normal are not properly calculated by the shader, thus causing the odd lightning (you see stripes along the surface of the sphere, stripes whom intensity is depending on the object position)

The lowest I can track this issue is here : https://github.com/BabylonJS/Babylon.js/blob/master/src/Shaders/default.vertex.fx#L130

It seems the matrix operations :

transposeMat3(inverseMat3(normalWorld)) 

Does not returns the expect result.

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 66.0.3359.181  Channel: stable
OS Version: OS X 10.11.6
Flash Version: 

It will work well with Chrome + Windows, or Safari + IOS, as far as I know it would be specific to Chrome + IOS.