Need to understand the code

Hello,

I am presently working on visible light communication. I was trying the code to evaluate received power for Non directed Line of Sight communication (NLOS). The code is attached for refernce.

With respect to the code i have understood the following-

1. The declaration of transmitter parameters
2. Declaration of receiver parameters
3. Position of transmitter
4. Creating the mesh for room configuration

I need help in understanding the following

1. Need to create position vector for transmitter
2. Need to create position vector for receiver
3. How the position vectors of walls are defined
4. Code inside the for loop for reflected waves

Kindly help if anyone can