I've seen this stuff mostly around particle effect spawns, example ripped from the code:<br><br>MSG_Select(MSG_SV_DATAGRAM);<br>MSG_WriteByte(svc_explosion2);<br>MSG_WriteByte(Effects & EF_DLIGHT_MASK);<br>MSG_WriteShort(ftoi(Origin.x));<br>MSG_WriteShort(ftoi(Origin.y));<br>MSG_WriteShort(ftoi(Origin.z));<br>Effects &= ~EF_DLIGHT_MASK;<br><br><br>Where is "MSG" being written?  What is MSG_SV_DATAGRAM?  How does this all lead up to spawning a particle array?  (I can guess those are just parameters fed one-by-one to some memory array in the main source code)  The greatest question then also is, where is, say, "svc_explosion2" defined, and what exactly is the format of such a thing?

This is user extended network protocol. MSG_SV_DATAGRAM means that commands will be written to the server's datagram or unreliable message. svc_explosion2 and similar are defined in shared game files, such as doomdef.vc and are parsed in client progs file effects.vc.