Modification of the orientation of normal vector

I think I understand how to implement the code for NORMAL VECTOR inside the tag <triangle>.

However, if I modify the orientation of normal vector for one or more triangles I don’t observe any change when I visualize my model inside the Collada viewer (I use Skechtup 7 Pro and Google Earth). :cry:

Why? Is the normal vector use to identify the face culling?

Instead, the inversion of triangle winding order works properly and produces the inversion of the front-side with back-side. Any help? Thank you.

What viewer are you using?

COLLADA stores vertex normals. An application can choose to use them or not. It sounds like the viewer you are using is ignoring the stored normals and computing normals.