Control of Particle Emission Upon Sit/Unsit

Hi All, I am looking for info on the commands that will start particles emitting when an AV sits on an object then stop the particles when the AV unsits. I am familiar with "touch_start" using if/else to start and stop particle emissions ( ParticleStart()/ParticleSystem([]) ). Looking for something like that for AV sitting. If someone can point me in the right direction, I would greatly appreciate it!

The event that's triggered when an AV sits/unsits on an object is «changed»...

Here's the wiki-link:

http://www.lslwiki.net/lslwiki/wakka.php?wakka=changed

Take a look at any of the sit scripts around.
The basic process is
1) Set a sit target
llSitTarget( Target, r );
2) A changed event is triggered with an av sits
changed(integer change)
{
//this checks to see if anyone has sat/gotten off the stand
if (change & CHANGED_LINK)
{

agent = llAvatarOnSitTarget();

//insert call to particles here

if ( mkLoungingAgentKey == NULL_KEY && agent != NULL_KEY )
{

//changed user
//cache new user key and request their permissions
mkLoungingAgentKey = agent;


}
else if ( mkLoungingAgentKey != NULL_KEY && agent == NULL_KEY)

//user is getting up
{

//stop particles

}


II) An alternate method that I use is llGetNumberOfPrims(). Get the number on_rez and if the number increases I assume it's a because an av sat on it and if the number decreases I assume a av got up. (It helps with teleporting av's who didn't stand first).

That's very interesting. But I'm not sure why it's different--wouldn't a CHANGED_LINK event get triggered on TP? Or, if that's the event where the decreased link count is found, does llAvatarOnSitTarget() not always get nulled when the agent TPs?

I first start using the prim count when I wanted a function to start when two avs sat on a multiprim object and stop if one of them left (either stood up/tp/crashed). The regular sit checking functions did not work (or I didn't understand it properly).

Thanks. That makes perfect sense: llAvatarOnSitTarget won't work if there's no sit target, and there can't be if more than one AV is to sit on the prim. Now that I think about it, I've used something similar where the script in another linked prim--not the one with a sit target--needed to know if somebody sat or stood. (As I recall, I walked the linkset looking for "prims" for which llGetAgentInfo looked like an agent, but that's the difficult way to do it. )

Thanks Destiny and Haruki! I even went a step further and included and animation. So much to learn... lol