LSL Wiki : Collisions

Collisions

In SL, a collision occurs when two objects make contact (impact, collide) in-world. Phantom objects do not cause collision events unless llVolumeDetect is used, except in the case of land collisions.

A script can have a stack/heap collision.

Attachments will not trigger collision events if the object itself collides with something else. However, if the avatar collides with the object, the collision event is triggered.

Note: collisons are not "touches", which is when a user clicks ("touches") on the object with their mouse cursor.

Function	Purpose
`llCollisionFilter`	Limits collisions to a specific name or key, so only collisions with a certain object(s) or agent(s) will trigger them.
`llCollisionSound`	Replaces or disables the sound the object makes when something collides with it.
`llCollisionSprite`	Replaces or disables the particles the object emits when something collides with it.
`llDetectedGrab`	Returns the direction the detected object is being dragged in.
`llDetectedGroup`	Returns `TRUE` if the detected agent/object is in the same active user group.
`llDetectedKey`	Returns the key of the detected agent/object.
`llDetectedLinkNumber`	Returns the link number that triggered the collison/touch event.
`llDetectedName`	Returns the name of the detected agent/object.
`llDetectedOwner`	Returns the key of the detected agent/object's owner.
`llDetectedPos`	Returns the position of the detected agent/object.
`llDetectedRot`	Returns the rotation of the detected agent/object.
`llDetectedType`	Returns the detected object type (`AGENT`, `ACTIVE`, `PASSIVE`, `SCRIPTED`).
`llDetectedVel`	Returns the velocity of the detected agent/object.
`llPassCollisions`	In a linked object, passes collison events from a child prim containing a collision event to the parent.
`llVolumeDetect`	Turns the object phantom and triggers `collision_start` and `collision_end` events when an agent/object intersects it.

Event	Triggered
`collision`	while agent/object is colliding with the object containing the script
`collision_start`	when agent/object starts colliding with with the object containing the script
`collision_end`	when agent/object stops colliding with with the object containing the script
`land_collision`	while the object containing the script is colliding with the ground
`land_collision_start`	when the object containing the script starts colliding with the ground
`land_collision_end`	when the object containing the script stops colliding with the ground

Example Script:

//By James Benedek
//Collision Detection
default 
{
        collision(integer num_detected)
        {
         if (llDetectedType(0) & AGENT)
        {
         llSay(0,"I Collided with an Avatar!");
        }
         if (llDetectedType(0) & ACTIVE)
        {
         llSay(0,"I Collided with a Physical Object!");
        }
         if (llDetectedType(0) & SCRIPTED)
        {
         llSay(0,"I Collided with a Scripted Object!");
        }
        if (llDetectedType(0) & PASSIVE)
        {
         llSay(0,"I Collided with a Object!");
        }
        }
        land_collision(vector pos)
        {
        llSay(0,"I Collided With Land!");
        }
}

Resources

tunneling, Andrew Linden, 5/29/05

Functions | Events | Detection | Physics

Has anyone tested the behavior of functions heavily dependent on the timing of each event, like llDetectedVel? If I want to get the velocity of my falling object an instant before the collision happens, do I call llGetVel in the collision_start event? Can I determine the time it took for two objects to collide by calling llResetTime in the collision_start event and llGetTime in the collision_end event?

Im trying to determine the force exerted upon an object due to a collision, and all formulas point to force = change in velocity / time. How can I measure the two required variables using the events provided? Is it possible?

-- ChristopherOmega (2005-07-12 11:47:24)