Weird noise when baking the vertex color

Hello everybody,

I followed some advice to bake my vertex colors into a texture map.

(https://blenderartists.org/forum/showthread.php?241389-Dirt-procedure&p=2035422&highlight=dirty+vertex#post2035422 and https://blenderartists.org/forum/showthread.php?247533-Baking-vertex-color).

But, even if the baking function works, i have a weird noise on the texture map. I searched on internet, but i found nothing.

Is anyone having an idea ?

Thanks !