|ind||The index of the particle type to change.|
|alpha1||The alpha of the particle.|
This function is used to set a particle type to have a single
alpha value (transparency) for the total duration of the lifetime
of each individual particle, and this can be from 0 (transparent)
to 1 (opaque).
The above code will set all particles created of the particle type indexed in the global variable "Snow_Part" to have an alpha value of 0.5 (semi-transparent).