Detecting if an object is on a surface

Hullo all, I'm making a vehicle that will go into different modes depending on whether it's airborne, in the water or flying. Detecting water and ground is easy enough, thanks to llWater and llGround.

But how do I detect if the vehicle has landed on (for example) a skyplat or other flat, non-ground surface?

It's not as easy, but use the collision_start event, and use the llDetectedType() and llDetectedPos() functions to determine a) that it actually is a prim surface (ACTIVE | PASSIVE), and b) that it actually is underneath.

Hmmmm......so something like:

integer airborne=TRUE;

default 
{
    collision_start(integer num_detected) 
     {
       vector pos = llGetPos() - <0,0,1.0>;//put an offset in for the aircraft gear length
       if (pos.z > llDetectedPos())
             {
             if (llDetectedType(0) ~ AGENT)
                {
               airborne=FALSE;
                }
              }
       }
 }

One thing I'm really sure I've got wrong is the detected type line. Basically, I don't want it to land on an avatar. The wiki says llDetectedType returns a bitfield, so you have to use bitwise operators, something I'm really not good at. How should I write that if statement so it returns true if the detected type is anything but an agent?

I think llDetectedType comparisons need to be an AND check, like:

if ( llDetectedType(0) & AGENT )

So that doesn't solve your problem really. I would try something like this:

default
{
collision_start(integer collided_number)
{
integer agentCheck = llDetectedType(0) & AGENT;
if ( !agentCheck)
{
llSay(0, "Raar!";
}
}
}


I'm not really sure that would work either and since SL is still offline I can't double check it right now.

Worked perfectly, thanks!

You're quite welcome!