# Transmission / Penetrations Along Rays

The number of transmissions / penetrations are not limited in the rays considered for the
computation. The transmission/penetration loss of an object intersecting any ray must be
added to the free space loss *L _{FS}* of this ray:

An object is defined as a planar polygon. The material properties of the objects can be defined individually.

The determination of the intersection between a ray and an object is explained with a simple example. If more objects must be considered, this analysis must be made for each object individually.

*n*

_{W}.Consider the transmission of the ray between the two points *P _{1}* and

*P*. The point

_{2}*Q*is computed as the intersection between the line represented by

*P*and

_{1}*P*and the object (described by the normal vector

_{2}*n*and its distance to the origin of the coordinate system). If

_{W}*n*is parallel to the direction from

_{W}*P*to

_{1}*P*, no transmission / penetration is assumed.

_{2}*Q*is between the points

*P*and

_{1}*P*and if

_{2}*Q*is inside the polygon representing the object, a transmission / penetration occurs and its transmission/penetration loss (material dependent) must be added to the free space loss of the ray between

*P*and

_{1}*P*. If

_{2}*Q*is outside the polygon or not between

*P*and

_{1}*P*, no additional loss due to transmission / penetration must be considered.

_{2}