Collision Detection in non-physical items?

I'm currently making a gadget that generates a little critter every so often that will dash about madly for a minute or so before disappearing in a puff of sparkles. It mostly works ok... but I've so far failed to figure out how to get my little critter to cope with walls and other objects in its path. It just scuttles through them as if it were phantom (which it isn't). Events like collision or collision_start just don't seem to register at all when I use them.

Is it possible to get a non-phys item to detect an item in front of it or touching it? I'm hoping to avoid using physics for this task since my little critter contains more prims than the physics engine will allow.

What do folk recommend I do?

You could use sensors to search for objects around the critter, and then move it accordingly

give it whiskers and use in conjunction with volume detect... I think that might work for you

Could you expand on that a little? How will whiskers make it work better, assuming that the whiskers are also non-physical (which they'd have to be)?

That would work for avoiding walls and such? The LSLWiki says: "The sensors detect objects only if their center falls in the detection cone (see below). This makes it harder to use sensors for pathfinding, especially avoiding big objects like walls." Is there a good workaround for this that you know of?

the 'whiskers' would be sensing devices, probably 100% transparent, when they colide with an object they would return a collision eevent that could be used to trigger a change in direction. I'm pretty sure the object center doesn't need to pass through 'whiskers' to trigger the event.

basic premise, object moves, whisker comes into contact with another object, collision is triggered, object takes actions until collision end is triggered. very useful for non-physics useage

Ah, gotcha! Yes, that does sound useful! I shall give it a go and see if I can get it to work. Thanks for the tip!

Okay, my newt now has a whisker sticking out the front of its head. I can't get the dratted thing to actually do the collision detection thing successfully yet, though. Here's a little simplified testing script containing the collision code I'm using... what have I done wrong?

default
{
state_entry()
{
llVolumeDetect(TRUE);
llOwnerSay("checking for collision";
}

collision_start(integer num_detected)
{
llSay(0, llDetectedName(0) + " collided with me!";
}
}


Note that it is in the root prim of the newt critter. I have another separate script providing forward motion; I'd anticipate that when the whisker started to interpenetrate an obstacle in front of the newt, this little script would trigger a message saying that collision had occurred. (I swiped the "collision_start" function directly out of the LSL wiki to avoid inadvertant typos.)

But it's not working. I must be missing something here. Any idea what it is?

You didn't miss anything... I did...

uhm volume detect will only detect items with physics enabled... av's vehicles, etc.... I just rechecked it myself.... and now feel like an idiot

physics of course would be the easy answer (except for the prim count) and you've already guessed the worst part of the sensor issue (it detects object centers)... I really don't see an easy way around this other than tailoring the environment, or preloading the limitis your critters can use.

Darn.

Well, physics ain't really an option, since to get the prim count down to a level where that would be workable, my critter would lose its refined and newtly appearance. Although I could try and see if I could get it at least tolerable... *sigh*

I guess the other option is Plan B, which is to pass my Newt Emitter off as a Ghost Newt Emitter - now with amazing Walk Through Walls action! Not quite what I had in mind, but if I made the newts semi-transparent and added a ghostly sound effect, I could possibly get away with it. *wry laugh*

sorry (but hey that's good marketing) .... why so high on the prim count these little newts? any possibility that some of their slick skin could be remapped with sculpty parts? texture hacks? terribly tortured torii??

It's coz of their animated walking action (done by duplicating the limbs and making them alternate between transparent and non-transparent, to a time). That and their cute little toesy-woesies.

I'll have a play with one tomorrow and see how much I can reduce the prim count by. I do already have a sculpty on it for a head. It's the limbs that are the challenge. But I shall see what I can do, later on.