Face revive specular from opposite side of normal (Dirty lens effect)?

Hello,
I’m trying to create a dirt-mask like effect in blender, where the camera lens looks scratched and grimy. The problem is that while the plane’s texture of scratches and dirt need to face the camera for the “dirty lens” effect, while the plane needs to be receiving light from the opposite direction.
Here’s an example:

Basic Setup:


When I face towards the light (When I want the plane to have specular lighting:


When I face away from the light (When I don’t want the plane to receive specular lighting, but it does due to normal orientation):


Does anyone know how to make a face receive it’s specular lighting from the opposite of the normal? Or is there another way of setting up a dirty lens effect? Thanks for any tips!

Write a custom shader?

EDIT: Alternatively you could use a node material.

There was another peron not long ago with the same problem, thought he solved it, maybe worth a search.

#edit looked it up for you

the solution:

thread:
https://blenderartists.org/forum/showthread.php?423434-BGE-Lens-Dirt-Help

Ooh nice, that works pretty well : D

Edit: That tutorial was fun, thanks for sharing! Kudos, Cotaks : D

Attachments

Dirty_Lens_Test_00.blend (611 KB)