Thanks^^
I corrected a bug i found in my function.
I was emitting many times (as much as the distance covered ! Ouch !!) the same walls. I couldn’t see it while walls were 90° oriented (as they covered each other perfectly) but the horrible truth appeared when setting a random orientation !
So i added an array of vectors to check if anything has already been emitted at a location.
The array is cleared in the event graph and is the correction in the function:
The corrected asset has been reuploaded 
Cheers