Calculating particle normal velocity using UDF
 

Hi all

I need to calculate the normal velocity of a particle when it hits a wall in my UDF. I know it is the dot product of the normal vectors in each direction and the normal velocities in the corresponding directions. Could someone tell me how to obtain the normal vectors in each direction? Mine is a 3d case. Please explain as detailed as you can as I want to make sure I get this right before I move on.

Thanks

Prashanth